Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida)
RICHARD CIFELLI and GEORGE SCOTT
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Robert McC. Adams Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY • NUMBER 58
Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida)
Richard Cifelli and George Scott
SMITHSONIAN INSTITUTION PRESS City of Washington 1986 ABSTRACT
Cifelli, Richard, and George Scott. Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida). Smithsonian Contribu tions to Paleobiology, number 58, pages 101, 43 figures, 1986.—The histories of lineages forming the Neogene globorotalid radiation in the planktonic foraminifera are reconstructed primarily from stratigraphic distributions. Data on major taxa are synthesized, with particular reference to the devel opment of shell design, and related to biogeograpy and evolutionary strate gies. The radiation was established about the base of the lower Miocene by three groups {Fohsella, Globorotalia zealandica lineage, and G. praescitula plexus), which probably arose from separate paragloborotalid lineages. Common trends (size increase, chamber compression, keel development, reduced wall relief) early in the radiation culminated in the evolution of disk like taxa which, since the middle Miocene, have been centered in the tropics. The later phase of the radiation (post middle Miocene) was marked by architectural diversification as spiroconical (e.g., G. margaritae), ventroconical (e.g., G. truncatulinoides), and globose (e.g., G. inflata) taxa arose. Architec tural diversification may be linked with watermass differentiation in the late Neogene. Neogene designs have close counterparts in the earlier, but phyletically isolated, Paleogene and Cretaceous radiations. There are also resemblances in ontogenetic strategies and lineage histories. Common adaptations are suggested, but specific functional explanations have not been established. Periods of major redesign are recognized in most lineages and are not confined to speciation events. Examples of stasis in adult morphology occur particularly in taxa that have evolved compressed, keeled shells. Bifurcations in lineages are indistinctly represented by wide spectra of morphotypes. Within the radiation very rapid speciation events are conspicuously absent, although they possibly occurred at the origin of some lineages. The distinctly sluggish tempo of change may be due to large population sizes and their degree of intercommunication. Good examples of allopatric and parapatric speciation were not found, but the prevalence of polytypic taxa, often distributed in contiguous populations showing clinal variation, would favor the inception of parapatric speciation.
OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The trilobite Phacops rana Green.
Library of Congress Cataloging in Publication Data Cifelli, Richard. Stratigraphic record of the Neogene Globorotalid radiation (Planktonic foraminiferida). (Smithsonian contributions to paleobiology ; no. 58) Bibliography: p. Supt. of Docs, no.: SI 1.30:58 ]. Globorotalia, Fossil. 2. Paleontology—Tertiary. 3. Geology, Stratigraphic—Tertiary. I. Scott, George II. Title. III. Series. QE701.S56 no. 58 560s [563'.12] 84-600360 [QE772] Contents
Page Introduction 1 The Neogene Succession of Globorotalids 4 Root Stocks 4 Major Evolutionary Trends 7 Origins of the Early Lineages 13 Fohsella Lineage 16 Globorotalia zealandica Lineage 19 Globorotalia praescitula Plexus 21 New Zealand Record of Globorotalia miozea 24 Encrustation 25 Northern Representatives o^ Globorotalia miozea 27 Summary of the Early History of the Plexus 29 Early Spirally Convex Forms 30 Globorotalia conoidea-Globorotalia menardii Divergence 32 The Conservative Branch, Globorotalia conoidea 32 The Innovative Branch, Globorotalia menardii 35 The Scitulines 39 Globorotalia tumida Lineage 44 Later Developments 46 Globorotalia inflata Lineage 46 Globorotalia crassaformis Plexus 49 Origin 50 Relation to Globorotalia inflata Lineage 52 Keel Development 52 Globorotalia crassula 53 Globorotalia truncatulinoides 54 Analysis of the Succession 58 Globorotalid Radiations 58 Overview 58 Evaluation 65 Biogeography 66 Some Precepts 66 Adaptive Strategy 69 An Historic Perspective on the Evolution of Form 71 Bathymetry and Architecture 76 Evolutionary Patterns 78 Shape of the Phyletic Tree 78 Pattern in Individuals 79 Pattern within the Tree 81 Evaluation 84 Retrospect 88 Literature Cited 92 iii
Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida)
Richard Cifelli and George Scott
Introduction Fossil planktonic foraminifera have been stud summaries hardly do justice to the record avail ied primarily from a geologic point of view. able. Indeed, the documented record ofthe Cen Research was stimulated through the expansion ozoic planktonic foraminifera is matched by few of oil exploration that followed the second world groups of organisms. This sort of record ought war and from a newly gained awareness by the to be ideally suited for in-depth evolutionary industry of the advantages of long ranged, inter studies that could provide a good background to continental correlations that could be obtained assess current theories and models. There are at by means of the widely distributed planktonic least two reasons why full advantage has not been foraminifera. Additional opportunities for study taken of the planktonic record in this respect. of the history of foraminifera in geologic context One reason is that biostratigraphers have were provided by the Deep Sea Drilling Project higher priorities than evolution. Their zonations (DSDP), which has resulted not only in an im are constructed using events (appearances and proved biostratigraphic framework and a cali extinctions) that occur in fixed stratigraphic or brated time scale but also in solutions to problems der. Lineages tend to be treated as stratigraphic in tectonic and climatic history. successions of morphotypes and species concepts The paleobiologic aspects of planktonic fora are sometimes quite arbitrarily restricted to spec minifera, by contrast, have received relatively imens closely resembling the type specimen. Usu little emphasis so far. On occasion, biostratigra- ally, no information is given about population phers have considered the evolutionary implica structure, and it is uncertain whether one or tions of their work and proposed phylogenetic more morphotypes may be present in the devel schemes (e.g., Walters, 1965; Berggren, 1966; opment of lineages. Lineages that contribute McGowran, 1968; Blow, 1969; Jenkins, 1971; events of little stratigraphic value are generally Srinivasan and Kennett, 1981b; Kennett and Sri- ignored, even though they may provide critical nivasan, 1983). For the most part, however, their links in the line of development. Therefore, it is difficult to obtain insight into the dynamics of Richard Cifelli, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. transformation from most biostratigraphic re 20560 (deceased). George Scott, Department of Scientific and ports, even though they contain important doc Industrial Research, Geological Survey, Lower Hutt, New Zea land. umentation about species occurrences. 1 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
The other reason for the lag in evolutionary or more feet thick (e.g., Arkell, 1933). Plank interest is perhaps more compelling, but much tonic foraminifera are generally found continu more subtle, because it involves a question of ously, although not always abundantly, through attitude about foraminifera that is rarely con out marine sequences outside of very near shore, fronted directly. As pointed out by Lipps (1981), shallow facies; in pelagic facies they are very ever since Carpenter (in Carpenter, Parker, and often remarkably continuous and abundant in Jones, 1862) denied that foraminifera had un distribution. A few grams of residue often con dergone any significant change since the Paleo tains a larger sample than the 352 (approxi zoic, a view upheld by Darwin, the foraminifera mately, incomplete data) primate teeth from 59 have been relegated to a role of "secondary citi samples used in an evolutionary study by Ginger zens" in evolutionary biology. Chiefly responsible ich and Simons (1977, text-fig. 10). Moreover, for the origin of this attitude was Dujardin because of their small size, a refined sampling of (1835), who discovered that the foraminifera populations is possible, sometimes to a nominal were single celled and relegated them to the resolution of about 1000 years, even in slowly "lowest forms of life." This attitude has persisted. deposited deep sea sequences (Schindel 1982). Van Valen (1965) remarked of foraminiferal re The planktonic record, however, is not always as search that, despite material scarcely paralleled it would seem. There may be facies influences in abundance, little of value for the general study on morphology. Size, extent of secondary calci of evolution has appeared from it. Even today, fication, and some aspects of form (e.g., axial probably few evolutionary biologists believe that shape in the group studied here) vary appreciably the record of planktonic foraminifera can reveal between open ocean and neritic environments. much that is of importance. Lipps (1981) empha Occurrences of planktonic foraminifera are spo sized the backwardness of biologically oriented radic in the excellent marine Tertiary sequence research. We will not argue the question of of California and they are poorly represented in whether or not there is a fundamental difference parts of the Mediterranean succession. Recovery in evolutionary potential between protozoans of planktonic foraminifera from deep sea cores and metazoans, but merely point out that there is sometimes poor because of local unconformi is a demonstrable historic order in the develop ties and dissolution of tests by diagenetic proc ment of planktonic foraminifera that compares esses (e.g., Berger, 1971). Bioturbation may af favorably with that of metazoans (Cifelli, 1969). fect the resolution of the record, but more seri Whether the pattern of planktonic development ous are the very large regional gaps between is typical is yet to be resolved; the point is that outcrop sections. Many important parts of these the record of planktonic foraminifera is about as gaps are being filled by the DSDP, but even at good a documentation as there is about the phy eupelagic sites there may be extensive hiatuses letic development of a group. Any evolutionary (Moore and others, 1978; Keller and Barron, model that ignores, or cannot account for, this 1983). At such sites stratigraphic completedness record is inadequate. (Sadler, 1981) may be as low as 1% at the 100- The quality of the planktonic foraminiferal year scale of resolution (Schindel, 1982). Despite record should be placed in perspective, because many local gaps or imperfections, however, there while it may be considered excellent, it is excel appears to be no global loss of the planktonic lent only in a relative sense. It still has limitations. foraminiferal record over the last 20 m.y. that Relative to a group such as the ammonites, the inhibits reconstruction of the history of the planktonic record appears superior because am group we study. In a piecemeal fashion the res monites are often concentrated in shell beds, olution of the record, at one or more locations, perhaps a few tens of feet or less thick, which are is probably always better than 0.05 m.y. separated by clays and silts, perhaps one hundred We use this record to trace the history of the NUMBER 58 3 major Neogene to Recent globorotalid lineages. tative. However, the latter method is assisted by Although diverse architectures developed, the the density of the record and the relatively slow lineages are linked by several common trends progress of character trends. Effectively, we are and demonstrate particularly well the iterative suggesting a version of phenetic linkage as out pattern of planktonic foraminiferal evolution (Ci lined by Gingerich (1976). Evaluations of char felli, 1969). A synthesis ofthe extensive biostra acter polarities are used only when stratigraphic tigraphic data about the lineages should assist in evidence is inadequate. This occurs particularly understanding their evolutionary patterns. at the origin of the radiation. Recognition that a group has a good fossil The study focuses on evolution at the species record calls for comment on methodology and level and, within the radiation, the record is often objectives. For Neogene biostratigraphers there adequate to provide evidence of taxonomic tran is a need to review the morphology, distribution, sitions. However, we do not consider that phy and relationships of taxa used in zonations. While logeny can be literally read from the rocks. Dif biostratigraphers can, and do, pursue their ob ferences between our interpretations and those jectives without knowledge of phyletic history, of Kennett and Srinivasan (1983) are witness to there is little doubt that such information, to the equivocal nature of the record in some in gether with an understanding of population var stances, but we consider that the gross form of iation and biogeography, can raise the accuracy the phyletic tree can be estimated from the stra and resolution of zonations. The scrutiny of the tigraphic record. Paul (1982) provided a theo stratigraphic record needed to meet this objec retical justification for this approach. Compara tive is also appropriate for studying the history tive morphology provides a secondary approach of globorotalid shell design and adaptation and to the assessment of phylogeny. Its use is pro for assessing the tempo of character evolution. moted by the prevalence of simple unidirectional Malmgren and Kennett (1981, 1982) provided trends in chamber design throughout globoro good examples of the resolution attainable in talid lineages. In several examples, the polarities character mappings of Globorotalia from the fos of important trends (increasing compression of sil record. chambers, development of keel) are clearly de When Eldredge and Gould (1972) challenged fined by stratigraphic evidence, and accord with the model of gradual phyletic evolution, they architectural and structural considerations. Po generated a need not only for new observations larities so confirmed are relevant to studies of of the stratigraphic record of lineages but also other lineages that have poor or inadequately for a re-examination of old ones. Although most researched stratigraphic records. We also at of the data we mention were collected for bio tempt to discriminate characters that are rela stratigraphic purposes, they warrant considera tively stable (effectively plesiomorphic in cladistic tion in light of questions about evolutionary terminology) from those in which major archi mode and tempo. Here, magnetostratigraphy tectural changes occur. The former are useful in now provides a sound chronologic basis for as identifying lineages; some transformations in the sessment of evolutionary rates. Therefore, with latter group are remarkably similar among line out apology to methodologists like Cracraft ages, and we consider their functional role (1974) and Patterson (1981), we interpret the through reviews of biogeography and compari phylogeny of Neogene globorotalids primarily sons with earlier globorotalid radiations. from the stratigraphic record. Ideally, this is While this study is eclectic and lacks the inter done by identifying sequences of populations in nal consistency of cladistic methodology, it allows which variation fields overlap but, because of the for multiple approaches to the estimation of an small amount of biometric mapping, most esti cestry. We do not attempt to minimize conver mates of continuity between samples are quali gences (cf. Eldredge and Cracraft, 1980); neither SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY do we eschew character reversals (a bete noire of tionships that such a study must address. cladistic theory). Indeed, there is good strati Biostratigraphers and evolutionists remain rel graphic evidence of such an occurrence in the atively isolated groups who pursue quite differ origin of a major Neogene lineage. We recognize ent research objectives and often neglect each the limitations of the fossil record but do not others' theory and data. This is mutually disad consider they inhibit valid inferences about vantageous. We hope this study allows both ancestor-descendant relationships. groups tojudge the value of a broader conspectus Only an overview of the Neogene globorotalid of the fossil record of a planktonic foraminiferal radiation is provided here. The treatment is un group. even and some taxa have been omitted, either ACKNOWLEDGMENTS.—We thank B.J. Burt, because we lack knowledge of them or because New Zealand Geologicail Survey, for taking some they appeared to be of minor evolutionary sig of the micrographs and for his great care with nificance. The study is further biased by our printing them. N. deB. Hornibrook and C.P. limited knowledge of lineage histories in some Strong, New Zealand Geological Survey, pro regions (e.g., Indian Ocean). A major formal vided valuable comments on the manuscript, and systematic revision of the group is desirable. M.A. Buzas, Smithsonian Institution, assisted While we do not attempt this, attention is drawn with its final preparation. to several outstanding problems in lineage rela
The Neogene Succession of Globorotalids
Root Stocks a globorotalid affinity, but some connection is indicated by the flattened spiral side and extra The development of the globorotalids, per umbilical extension of the aperture. haps the highlight of the Neogene planktonic A smooth wall, an important feature of ad radiation, had modest beginnings because of the vanced globorotalids, occurs in some Oligocene severe reduction of similar designs at the close forms, such as Globorotalia munda. However, this ofthe Paleogene. By early Oligocene, all lineages wall is more like the kind found in Globigerinita that had earlier achieved a globorotalid architec than in the globorotalids, as it has minute pores tural design were exterminated and few clues and pustules distributed more or less evenly on were left to the course of future development. all chambers (Figure la). There is no evidence Inferences from comparative morphology are that forms having this type of wall ever developed essential. The Oligocene faunas are character in a globorotalid direction. Fleisher (1974:1033) ized by simple, generalized forms, reminiscent of proposed the genus Tenuitella for such species, the assemblages found in temperate to subarctic and it is likely that this group developed indepen regions today (Cifelli, 1969). Prominent among dently. Oligocene faunas is Paragloborotalia, a genus that Walters (1965), McGowran (1968), and Ken in many respects compares closely with the mod nett and Srinivasan (1983) proposed the Oligo ern Neogloboquadrina pachyderma and N. in- cene group of species centered around Paraglo compta. Paragloborotalia has inflated chambers, a borotalia opima (e.g., P. nana, P. pseudocontinuosa, spherical profile, and a coarse wall that is ridged and P. semivera) as a globorotalid root stock and, and often honeycombed (Figure \b-c,f-g). At in view of the limited options available, this in least some species o^Paragloborotalia are spinose, terpretation serves as a reasonable first approxi with a texture comparable to that of the modern mation. However, with one possible exception Globigerinoides (Cifelli, 1982). The coarse wall (Srinivasan and Kennett, 1981b), transformation and inflated chambers are not at all suggestive of series have not been identified and specific con- NUMBER 58
FIGURE 1.—a, e, Globorotalia munda ]enk\ns, S127/f422, Waitaki Valley, New Zealand, lower Oligocene, topotype, (a, X 260; e, X 1430); b,f, Paragloborotalia ciperoensis (Bolli), 18-1-2 (R. Cifelli), PTrinidad {b, X 180;/, X 750); c, g, Paragloborotalia opima (Bolli), 40-3 (R. Cifelli), PTrinidad (c, X 130; g, X 660); d, h, Paragloborotalia pseudocontinuosa (Jenkins), N2/f554, Parengarenga Harbour, New Zealand, lower Miocene, topotype {d, X 200; h, X 355).
nections remain obscure. Although we focus on formation from paragloborotalids occurred? the paragloborotalids, it may be premature to There is really no good reason to assume that regard them as the only potential ancestral this was the case, because the paragloborotalids group. While the later chambers of Globorota were not totally replaced by the globorotalids at loides (a widespread taxon in the Oligocene) are the end of the Oligocene. For example, the typ globigerine, the early chambers closely resemble ically Oligocene Paragloborotalia opima group is those of Globorotalia. Did some globorotalids succeeded in the Miocene by species variously arise by neoteny? This merits investigation (N. referred to as Globorotalia mayeri, G. siakensis, deB. Hornibrook, pers. comm., March 1984), and G. continuosa, which show no globorotalid despite the prevalence of recapitulatory patterns advancement and therefore belong with Para in globorotalids. globorotalia. Bolli and Saunders (1982) viewed One of the major unresolved questions in glo the latter two species as junior synonyms of G. borotalid evolution concerns the actual number mayeri and extended the range of G. mayeri down of connections with the paragloborotalids. In the into the late Oligocene, emphasizing that the early Miocene, three distinct globorotalid lines paragloborotalids can be viewed as a long rang with self-contained histories can be recognized. ing group with the potential for repeated globor Was the early Miocene the only time that trans otalid development. In the late Cenozoic there SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
> ? 1S T CD N22 a. 4 " N21 ^ s ppe r CENZIA N UJ D •X Z N20 u •S3 P S
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_ UJ E SER R Nil 15 mid d N10 rVUIDA N9 scrrvLA N6 H UNEABE 3 N8 !5 PLEXUS FOHitlLA - N7 UNI AGE 20 ffi PnAESCfTVlA lowe r PIEXUS - N5 ZEAIAHDKA NEOGENE GLOBOROTAUD PHYLOGENY UNEA6E ,_ N4 Q U derived from biostratigraphy < FIGURE 2.—Phylogeny of Neogene globorotalids showing major groups and selected taxa. (Species ranges in Fohsella lineage partly after Blow (1969); in menardine taxa after Berggren and Amdurer (1973); in G. tumida lineage partly after Blow (1969) and Srinivasan and Kennett (1981a, 1981b); in G. praescitula plexus partly after Catalano and Sprovieri (1971), Berggren (1981), and Hornibrook (1981 b); in G. scitula plexus partly after Catalano and Sprovieri (1971), Wernii (1977), Perconig and others (1980), Berggren (1981), and Hornibrook (1981b); in G. crassaformis plexus partly after Rogl (1974), Stainforth and others (1975), Zachariasse (1975), and Berggren (1981); calibration of zonation after Berggren (1981).) NUMBER 58 are several advanced globorotalid groups whose morphotype involved a change in the shape of origins are obscure and the possibility of inde the chamber on the spiral side, to narrowly radial pendent development from paragloborotalid in Fohsella, and to elongate in the direction of ancestors cannot be ruled out. A tree with a coiling in Globorotalia (e.g., G. incognita). The single root has been proposed from biostrati earliest representatives tend to have chambers graphic data (Steineck and Fleischer, 1978). that are intermediate in shape. In the major However, our reconstruction (Figure 2) takes Globorotalia plexus (G. praescitula), the new shape cognizance of the limited stratigraphic and mor was fully established in the earliest representa phological evidence that there are probably mul tives (Figure 6o). Once established, the new tiple roots. chamber shapes remained relatively stable. Closely correlated with these spiral side Major Evolutionary Trends changes is compression of chambers. Once the chambers were transformed in shape, some de As a basis for examining the historic develop viation from the paragloborotalid axial profile is ment of the Neogene globorotalids, we review visible. This change was gradual, as both the their major advances over the paragloborotalids: early Fohsella and Globorotalia are only slightly (1) The wall surface is nonspinose and smooth, compressed and their profiles deviate but little although pustules are commonly present; the from the spherical profiles of the paragloboro ridged, honeycomb topography of paragloboro talids (Figure 7, compare G. incognita with Para talids is obliterated (Figure 3). (2) Whereas par globorotalia opima; Figure Sm). Later, they be agloborotalid chambers are quasi-spherical as in came increasingly subangular to angular and, globigerinids, globorotalid chambers are com finally, acute. pressed and the axial profile is angular (Figure Flattening of the wall also occurred early, but 3); compression increases during ontogeny. (3) A a fully smooth surface was not attained until the keel is developed as a fold in the chamber wall profiles became acute and keels were formed. (Figure 4); in the earlier globorotalids this fea Transformation may have involved a change in ture is a late ontogenetic development, but in regulatory balance of the calcifying processes. more advanced forms it occurs through most of Wall relief lowered from honeycombed to flat the test; there is no comparable structure in tened, and eventually became smooth as cham paragloborotalids. (4) The shape ofthe chambers bers became reinforced less by ridge develop on the spiral face (Figure 5) is modified from ment and more by the addition of sheet-like broadly radial (I-type) to either narrowly radial laminations. In Fohsella, flattening and smooth- (T-type, characteristic of Fohsella) or elongate in ening occurred in a reasonably uniform fashion, the direction of coiling (A-type or B-type, char as the wall is at first coarse, then generally be acteristic of Globorotalia); a flaring (C-type) comes decreasingly honeycombed with succeed chamber develops later (characteristic of the G. ing species and finally smooth with the arrival of menardii group). the keeled form. In the principal Globorotalia These advances began near the base of the plexus, development was more variable. The ear Miocene (Zone N4) and were fully achieved by liest forms of G. praescitula are quite smooth- the middle Miocene (Zone N12), when com walled, with only slight honeycomb texture (Fig pressed, fully keeled, smooth-walled globorotal ure 60-5); but these may be succeeded by forms ids had developed. At this stage, globorotalid with coarser textures and more clearly defined architecture was fully established, and later de ridges. As in Fohsella, a totally smooth wall was velopments primarily concerned details of cham not achieved until the profile became acute and ber form and coiling geometry. a keel formed. Once fully achieved, the smooth The first deviation from the paragloborotalid wall was always retained and there was no rever- FIGURE 3.—a, h, Globorotalia conoidea Walters {a, cotype locality Paragloborotalia mayeri Zone, Trinidad, middle Miocene, Trinidad example of "form 3" morphotype of Tjalsma (1971), X 345; h, N98/f565, Waimata Valley, New Zealand, topotype, middle Miocene, X 245); b, Globorotalia cultrata (d'Orbigny), Atlantic Ocean, 22°07'N, 81°08'W, 270 fathoms, Recent (X 240); c, Globorotalia menardii (Parker, Jones, and Brady), type locality Paragloborotalia mayeri Zone, Trinidad, middle Miocene (X 240); d, Globorotalia tumida (Brady), Atlantic Ocean, 22°07'N, 81°08'W, 270 fathoms. Recent (X 60); e, Globorotalia praescitula Blow, S137/f615, Oamaru, New Zealand, lower Miocene (X 455); /, Globorotalia miozea Finlay, F5089, Grey- mouth, New Zealand, middle Miocene, topotype, (X 240); g, Globorotalia praemenardii Cushman and Stainforth, locality 13 (P. W. Jarvis), Lower Green Clay, Cipero Section, Trinidad (X 340). FIGURE 4.—Dissections of last-formed chambers: a, Globorotalia miozea Finlay, S68/f31, Dovedale Stream, New Zealand, lower Miocene(X 310); b,c, Globorotalia praemenardii Cushman and Stainforth, S44/f7l7, Stillwater Creek, New Zealand, middle Miocene {b, X 650; c, X 900); d, Globorotalia conoidea Walters, T26/fl75, Whakatahine Stream, New Zealand, upper Miocene (X 490). NUMBER 58 CHAMBER ENVEtOPES SPIRAL ORIENTATION A CLASSIFICATION SIMPLE CRASSAFORMIS GLOBOROTALIDS PLEXUS juanai trunca tulinoides tumida Type C TypeT praescitula ADVANCED MENARDINE ocrassula incognita crassaformis Type B3 (paragloborotalid) GLOBOSE SHELL exilis Type I SPIROCONICAL SHELLS C^ inflata^ Type B2 Radial extension by rotation opima FOHSELLA LINEAGE gibberula Type B1 praefotisi / I previous whorl attached margin' margaritae kugteri ••- coiling direction FIGURE 5.—Left, Classification of spiral shape of chambers (after Cifelli and Glafon, in press) based on the angular position of the leading margin and location of the trailing margin (types A-C) and the angle between these margins (types I, T). Types A-C describe the amount of outward (radial) rotation of the chamber envelope. Type C, utilized by menardine taxa, increases the diameter ofthe shell and is a technique for producing a large shell. Right, Some examples of chamber envelopes (last-formed or final chamber drawn from SEM micrographs). The segment of the attached margin abutting the middle whorl is thickened and its straight- line length is approximately constant in the drawings. This scaling illustrates the radial elongation of late-formed chambers in large biconvex, tumid, and discoidal taxa (Figure 7). In contrast, in the ventroconical Globorotalia truncatulinoides, in which the ventral surfaces are greatly extended, the spiral surface is relatively small. The slightly elongate, crescentic shape of a phyletically early taxon (G. incognita) quite closely resembles the semicircular envelope of Paragloborotalia opima, a possible member of its ancestral group. A-type crescentic chambers occur early in the G. praescitula plexus and are transformed to B and C types in most advanced members. Radial elongation of quasi-T-type chambers occurs in the Fohsella lineage and similar chambers evolved in G. tumida. As with type C, this is a technique for increasing the radial diameters of shells. Phyletically simple shapes occasionally occur late in the radiation. The envelope of G. juanai resembles that of a paragloborotalid and, although it is regarded as a scituline, it may represent a separate line of descent (Figure 2). 10 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY FIGURE 6.—a-f, i, Globorotalia praemenardii Cushman and Stainforth, J32/f 7589, Greymouth, New Zealand, middle Miocene {a,b, X 100; c, X 90; d,e, X 80;/, X 220; i, X 205); g,h, j-n, Globorotalia miozea Finlay: g-h, l-n, F5089, Greymouth, New Zealand, topotypes, middle Miocene {g, X 205; h, X 300; /, X 120; m,n, X 115);;,A, S68/f241, Waipara, New Zealand, lower Miocene (X 85). o-s, Globorotalia praescitula Blow: o,p, S136/fll59, 91-92 ft (27.76- 28.06 m), Awamoa Drillhole, New Zealand, lower Miocene (X 245); q, S136/fll59. 11.5 ft (3.51 m), Awamoa Drillhole, New Zealand, lower Miocene (X 170); r,s, S137/f615, Oamaru, New Zealand, lower Miocene (X 185); {p-r are in ascending stratigraphic order, left to right). NUMBER 58 11 sion towards a honeycomb texture. In G. zeal In most lineages the keel, once evolved, was andica lineage partial smoothing of the wall was retained by all descendants. Indeed, Blow (1969) achieved rapidly. considered that the keel was a fixed structure, Once the globorotalid test became fully devel incapable of complete suppression. However, in oped, subsequent architectural changes were re the Globorotalia inflata lineage, which arose from stricted primarily to chamber design and partic the compressed and keeled G. conoidea (a main ularly to the axial profile. Design changes within branch of the G. praescitula plexus), radial infla the spiral face of chambers were relatively minor tion of chambers resulted in reduction and even (Figure 5). C-type chambers arose in the menar tual elimination of the keel. The axial profile of dine branch of the G. praescitula plexus while, in G. puncticulata sensu stricto (Pliocene) resembles contrast, quasi-rectangular shapes arose in the G. that of G. zealandica from the lower Miocene. crassaformis plexus, notably in G. truncatuli The latter is phyletically close to the paraglobo noides. But most of the praescituline descendants rotalids; the former arose from a globoro remained conservative and retained the B-type talid ancestor in which the keel had been univer chamber without change. sal for about 8 m.y. A similar but less pronounced Spiral chamber shape is related to the number reversal may have also occurred in the scitulines, of chambers in the outer whorl. Fohsella is gen although their record is less clear. erally multi-chambered, with six or more cham No doubt there are some like Blow (1969) who bers in the outer whorl. A radially elongate shape look upon reversals of trend as biologically in permits chambers to be closely packed. Globoro defensible. Yet, what else can be read from the talia normally has only four to six chambers in stratigraphic record? Starting in the latest Oli the outer whorl and rarely only three. The few gocene or earliest Miocene, there is a singular short-lived menardine Pliocene species that ex trend towards the development of an acute pro perimented with arrangements of more than six file and keel, along with a smooth wall, that chambers, such as G. multicamerata and G. exilis, culminated in the middle Miocene. These acutely developed radially elongate chambers that profiled, mostly keeled forms are the sole glo closely approximate those of Fohsella. borotalids available for ancestry of the later rep The axial profile became modified in two prin resentatives of Globorotalia. If there was not a cipal directions: (1) The axial compression of reversal, then an independent connection with a chambers, which produced a disk-like shell, and later paragloborotalid must be envisaged. This is (2) the radial compression and extension of the not demonstrable for the G. inflata lineage. umbilical side of chambers, which produced axi- However, an actual case of direct transforma ally elongated chambers, culminating in a trun tion from a late paragloborotalid may be repre cated cone. Both architectures are most strongly sented by a form such as G. anfracta Parker (e.g., developed in mid-late ontogeny. Ultimate Poore, 1979, pi 2: figs. 8, 9). This species has a expressions of the two trends are Globorotalia totally smooth wall, but a spherical profile and cultrata and G. truncatulinoides, but there are chambers that are broadly radial. If a ridged, intermediaries. Throughout the radiation, the honeycombed texture were superimposed on the spiral side, with a few important exceptions, re surface, one would, with little hesitation, refer it mained flat or gently convex. The menardine, to Paragloborotalia. Yet, although smooth, the disk-like form became a stable design and little wall is not a typical globorotalid type. It is very architectural change occurred in the G. menardii thin and glassy in appearance throughout the group. On the other hand, the G. conoidea group, test, like the walls of early formed, unreinforced though conservative in other respects, retained chambers. Immature, honeycombed forms that greater plasticity and the early-middle Miocene have not yet reinforced any of their chambers by trend of globorotalid development was reversed secondary calcification may show a very similar in one branch. smooth, glassy surface (Cifelli, 1982, pi. 1: fig. 12 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY coiling — mons^ zealandica VBfmOCONICAL DISCOID GIOBOSE (inflated) mayeri opima truncatulinoides inflata NUMBER 58 13 1). The wall of G. anfracta lacks the distinctive FIGURE 7.—Axial outlines (in the plane of the coiling axis) laminations of Globorotalia and there is a total of taxa representing major Neogene globorotalid architec absence of pustules. Therefore, this distinctive tures. Drawings, from micrographs, are to a common scale and are of representative, mature specimens. The form of species may very well have quickly transformed the axial outline in these trochospiral shells is largely deter from a late paragloborotalid by a retardation of mined by the shape of chambers in the outer whorl, their shell growth. rate of expansion, and by the rate of vertical translation of In perspective, reversals in trends and loss of whorls along the coiling axis. There is much greater varia advanced structures were minor components of tion in axial shape of globorotalid shells than in spiral shape (defined by the equatorial outline of the outer whorl). The the radiation. They demonstrate the plasticity of difference may relate to the preferred orientation of the chamber form and the potential for advanced organism in water, but there has been no research. Lower lineages to change architectural directions. In Miocene taxa {Globorotalia praescitula, G. zealandica, G. in fact, few did so. The dominant feature of the cognita), which occur early in the Neogene radiation, have radiation is canalization of evolutionary advance shapes similar to the inflated discoidal form of paraglobor along a few, well-defined routes. otalids like Paragloborotalia opima and P. mayeri. Occasion ally, this form occurs later in the radiation (e.g., G. juanai). The dominant axial architectures have compressed chamber Origins of the Early Lineages margins. The primitive discoidal shape (inflated) is stretched radially to a large diameter in compressed discoidal taxa. The Neogene globorotalid radiation began Radial extension is assisted by the use of C-type chambers with the appearances of Fohsella kugleri, Globo (Figure 5). Biconvex and tumid shapes develop when mod erately inflated ventral surfaces of chambers approximately rotalia praescitula, and G. incognita in the early correspond with curvature of the spiral surface of the shell Miocene. These forms are the first to show a produced by translation of whorls along the coiling axis clear deviation from paragloborotalid architec {Fohsella fohsi, G. praemenardii, G. menardii, G. tumida). ture, and they are the progenitors of three sep Spiroconical profiles form when the rate of translation of arate stocks that achieved various degrees of whorls is high (quasiconical spiral surface), and the ventral success during the Neogene. Fohsella kugleri ap surface is depressed {G. margaritae, G. panda). In ventrocon ical shells the rate of translation of whorls is low (flattish peared first, in Zone N4, and was preceded in spiral surface), but ventral surfaces of late-formed chambers the late Oligocene (Zone N2) by F. mendacis, a are highly elevated (G. mons, G. truncatulinoides). In the form that still lacked well-developed globorotalid globose G. inflata, relatively low whorl translation is associ features. Globorotalia praescitula and G. incognita ated with rapid increment in size of the radially inflated both appeared later, in Zones N5-N6. chambers. While the diagram suggests common morpholog ical pathways, comparison with Figure 2 shows that several Jenkins (1971) recognized Fohsella periphero taxa with very similar profiles are placed in separate lineages ronda as the most primitive Fohsella and derived (e.g., F. fohsi and G. tumida; G. mons and G. truncatulinoides; that species directly from Paragloborotalia bella, G. margaritae and G. panda). Only a simple transformation an early Miocene form with an inflated profile, seems to be required to redesign P. opima into G. inflata, which shows some advancement towards a glo but the record (Figure 2) shows that the latter descended from biconvex to ventroconical populations with compressed borotalid in the flattening of the wall surface. peripheries. Lines of descent are sometimes much more Arguments against P. bella are that the chambers complex than analysis of the form of end members might are sometimes elongate in the direction of coil suggest. Generally, modification of the phyletically primi ing, which is more suggestive oi Globorotalia, and tive, inflated discoidal profile is associated with pronounced the number of chambers in the outer whorl is increase in size. This, together with good stratigraphic evi dence of convergence in axial shape, suggests that modifi lower than in Fohsella. An early form displaying cation to the primitive forms may be size-required responses distinct profile angularity is F. kugleri, which that have followed a few common plans. appeared close to the Oligocene-Miocene bound ary (Blow, 1969:350, about 23 m.y. ago on the time scale of Ryan and others, 1974, table 7). Kinship of F. kugleri to the succeeding Fohsella 14 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY FIGURE 8.—a~c, Fohsella fohsi (Cushman and Ellisor), type locality Fohsella lobata Zone, Trinidad, middle Miocene (X 90); d,e, Fohsella robusta (Bolli), near type locality F. lobata Zone, Trinidad (X 95); f,g, Fohsella praefohsi (Blow and Banner), cotype locality Fohsella fohsi Zone, Trinidad, middle Miocene (X 115); h-j,n,o, Fohsella peripheroronda (Blow and Banner) {h-j, type locality Globigerinatella insueta Zone, Trinidad, lower Miocene (X 150); n-o, locality 12 (P. W. Jarvis), Upper Marl, Cipero Section, Trinidad, middle Miocene (X 115)); k-m, Fohsella kugleri (Bolli), type locality F. kugleri Zone, Trinidad, lower Miocene (X 160). species was suggested by Stainforth and others principal difference between F. kugleri and de (1975:279) and the connection appears very scendant forms is its coarsely ridged texture, with close. Fohsella kugleri has the same narrow, radi projections from the ridge corners, suggesting ally elongate, T-type chambers that are charac that the species was spinose in its living state teristic of Fohsella and that show the beginnings (Cifelli and Glafon, in press). of distinct profile angularity (Figure 8A—m). The In texture, Fohsella kugleri compares favorably NUMBER 58 15 with Paragloborotalia ciperoensis (Figure If), a talid-globorotalid connection is Globorotalia in possible ancestor of Fohsella. Both species lack cognita (Figure 9a,e). Srinivasan and Kennett the regular honeycomb pattern of Oligocene (1981b:518) reported a transition between G. forms, such as P. opima, where the ridges spread incognita and Paragloborotalia continuosa, but laterally to enclose single pores (Figure Ig-). Some they did not show the chamber transformation. honeycomb patterning is formed on chambers of The loop-shaped aperture of G. incognita sug F. kugleri and P. ciperoensis, but not on all parts, gests affinity with P. semivera and P. pseudocontin and the spine-like projections may stand in iso uosa, and possibly P- acrostoma. Early represent lation without ridge support. Where ridges do atives of G. incognita have distinct honeycombed develop, they spread erratically and sometimes walls and subspherical profiles that are barely join to enclose two or more pores (Figures If distinguishable from the spherical profiles oi Par 8k-m). Paragloborotalia ciperoensis is a quasi-glo- agloborotalia (Figure 7). The only major advance bigerine form with a large, open umbilicus, but of G. incognita is a definite elongation of cham there is some extension of the aperture towards bers in the direction of coiling, seen on some the periphery. There is also minor flattening of individuals. With the appearance in the lower the spiral side. This species is comparable to the part of Zone N6 ofthe descendant G. zealandica, modern Neogloboquadrina dutertrei, which shows a globorotalid shell form with a partially flat wall similar quasi-globigerine features. is achieved. Fohsella kugleri has a narrow but distinctly Globorotalia praescitula is remarkably ad open umbilicus, which conceivably could be de vanced from the outset. Even the earliest repre rived from P ciperoensis. However, there is no sentatives are distinctly globorotalid with cham evidence of a transition, as the very primitive bers that are all distinctly elongate in the direc fohsellid, F. mendacis, has the same narrow um tion of coiling. The wall is nearly smooth, with bilicus as F. kugleri. Primitiveness of F. mendacis honeycombing retained only on the earliest is shown by its chamber shape, which varies be chambers. Features shared in common with tween the broadly radial I-type, characteristic of paragloborotalids are an elongate, narrow aper Paragloborotalia and the radially elongate T-type, ture and the four to five chambers in the outer characteristic of Fohsella (Blow, 1969, pi. 38: figs. whorl. Some tendencies toward a globorotalid 7, 8). Also F mendacis has a tapered profile that shell form can be seen in late-occurring Paraglo is neither distinctly spherical nor angular (Blow, borotalia species, such as P bella, which tend to 1969, pi. 38: fig 5). The wall is coarse and have flattened, although distinctly honey irregularly ridged as in P. ciperoensis and F. ku combed, walls and chambers that are somewhat gleri. Fohsella pseudokugleri shows no additional elongated. However, G. praescitula represents a stages in development. Chambers on the holo clear break with Paragloborotalia and its origin type of this species are consistently more radial has rightly been termed cryptic (Jenkins, than in F. mendacis, but appear to fall within the 1965:268). The derivation from any particular range of variation ofthe latter. Possibly, F. pseu paragloborotalid is speculative. In light of the dokugleri is a junior synonym of F. mendacis. Oligocene-early Miocene DSDP sequences that Keller (1981) reported intergradations among P. have been studied, the chances of finding addi kugleri, P. pseudokugleri, and P. mendacis. There tional links become increasingly remote but fore, while early Fohsella compare closely with should be searched for. The chamber shape and the paragloborotalids and a connection with P. flat wall of G. praescitula represents a major ciperoensis is suggested, the actual line of descent redesign that may have occurred through rapid remains obscure, both from comparative mor speciation. phology and from the stratigraphic record. This view of the origin of Globorotalia praesci The species showing the closest paragloboro- tula disagrees with those of Keller (1981), Srini- 16 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY FIGURE 9.—a,b,e, Globorotalia incognita Walters, S136/fll59, 48.5-49.5 ft (14.79-15.10 m), Awamoa Drillhole, New Zealand, lower Miocene {a,e, X 195; b, X 550); c,d,f-h, Globorotalia zealandica Hornibrook, S137/f615, Oamaru, New Zealand, lower Miocene {c,g, X 145; d,h, X 130;/, X 765). vasan and Kennett (1981b) and Kennett and they are treated here as a lineage totally distinct Srinivasan (1983). Keller (1981, fig. 3) depicts G. from Globorotalia. Trinomial nomenclature is not praescitula arising via G. cf. miozea from G. incog used as the relationship of the members is suffi nita. Srinivasan and Kennett (1981b, fig. 10) ciently indicated by their inclusion in the genus show G. praescitula branching from G. zealandica. Fohsella. In these papers the entry of G. praescitula is Bolli (1950; 1957) recognized the following shown to be subsequent to the evolution of G. sequence in Trinidad: zealandica sensu stricto. In New Zealand and at Fohsella robusta DSDP Site 516 in the South Atlantic (Berggren Fohsell lobata and others, 1983) the reverse occurs, suggesting- Fohsella fohsi that the sequences studied by Srinivasan and Fohsella peripheroronda (originally Globorotalia barisanensis) Kennett and by Keller do not contain the early This species group was later revised by Blow history of G. praescitula. Pending further data, and Banner (1966), who added Fohsella peri- we discount their reconstruction. pheroacuta and F. praefohsi as intermediaries be tween F. peripheroronda and F. fohsi. Blow and Banner also considered F. robusta and F. lobata Fohsella Lineage as varietal forms of F. fohsi and made no taxo Formerly, the members of this group were nomic distinction among them. Bolli (1967) ac designated as subspecies of Globorotalia fohsi, but cepted the addition of Blow and Banner's two NUMBER 58 17 new species to the Fohsella group but rejected test. Most of the flattening occurs in the final the grouping of F. lobata and F. robusta with F. chambers; the early chambers are almost as fohsi. Bolli was supported by Stainforth and oth coarse as the chambers in F. kugleri. ers (1975:276, 280) who pointed out that F. Fohsella peripheroronda is a long-lived species, lobata and F. robusta are not only larger, but which was cosmopolitan in the tropical and tem show greater advancement in keel development. perate regions during the greater part of its From examination of holotypes and other mate range. About the level of Zone NIO a split in the rial we are in agreement with this conclusion. In parent population occurred, with one part retain addition to having better developed keels, F. ing relatively primitive features and the other robusta and F. lobata tend to have smoother walls. part evolving into a rapid succession of increas However, we are uncertain about the distinction ingly advanced species. The split was accompa between F. robusta and F. lobata, and so we nied by geographic partitioning, as the evolving tentatively call these most highly advanced glo stock became increasingly restricted to the trop borotalid forms ofthe Fohsella lineage F. robusta. ics (Figure 34) and the parental F. peripheroronda To the above group of species, F. kugleri and F. retracted to higher latitudes. In New Zealand, mendacis are added here as the ancestral forms. the relatively primitive F. peripheroronda, or a Srinivasan and Kennett (1981a:4I0) previously close descendant, extends into Zone N14, but assigned Globorotalia kugleri to Fohsella. for the most part this species was unsuccessful It might appear that the Fohsella lineage (Fig after the split and beyond the Southwest Pacific ure 8) would serve as an example of phyletic is poorly known above Zone NIO. Middle Mio gradualism, since its development is seemingly cene populations transitional between Fohsella marked by a unidirectional, progressive series of peripheroronda and Paragloborotalia mayeri were increasingly advanced forms culminating in a noted by Jenkins (1966b:27, 1971:119) from this single type of globorotalid shell. However, region. Nominally, this is an important instance branching occurred along the line of descent, as of a globorotalid evolving into a paragloboro well as significant variation in the rate of devel talid. However, P mayeri has a long history in opmental change. The early representative of the tropics prior to the level of origin postulated Fohsella, F. kugleri, is a small lobulate form with by Jenkins in the Southwest Pacific. Hoskins five or more chambers in the peripheral whorl (1984) contrasted the honeycombed surface tex and a narrow, open umbilicus. It has an arched, tures of New Zealand specimens of P. mayeri with rather broad profile but is distinctly subangular, the smooth interpore spaces on the shells of F. rather than rounded as in F. mendacis. The wall peripheroronda and argued that they were not is very coarse, with well-developed ridges sur related. rounding single pores or distributed irregularly The evolving Fohsella robusta stock was short among the pores (Figure 8k—m). Occasional lived. Although paralleling and achieving the spike-like projections protruding from the sur same globorotalid architecture as Globorotalia, it face may be relic spine bases. become extinct soon after the time of most rapid Fohsella peripheroronda (Figure 8h-j,n-o) and important change. The evolving species sel shows small, but distinct advances over F. kugleri. dom wandered far beyond the tropics, and they Keller (1981) and Srinivasan and Kennett became increasingly restricted in distribution (1981a) reported intergradations between these (Jenkins, 1965; Saito, 1977; Figure 34). Fohsella taxa. The test of F. peripheroronda is more com peripheroacuta is the first species of the evolving pact, with a more rounded, circular periphery, branch and its principal advance over F. peri and a profile that is perhaps a little more suban pheroronda is the acquisition of a distinct, acutely gular, although still distinctly arched. There is angular profile that compares favorably with the some flattening of the wall in F. peripheroronda, profile of Globorotalia miozea and G. archeomen- but a ridged texture is retained throughout the ardii. Transformation may have been rapid but i: SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY was of long enough duration to leave a geologic There is some keel development in F. fohsi, but imprint. Jenkins and Orr (1972:1102) reported it is weakly formed and is not found on all a transition between F. peripheroronda and F. specimens. peripheroacuta in DSDP cores from the Equato Fohsella robusta (Figure 8d-e) is appreciably rial Pacific. larger than its predecessors. This form also dis The wall surface of Fohsella peripheroacuta is plays a small reversal in evolutionary direction, considerably smoother than in F. peripheroronda, as it has a circular outline like the earlier Fohsella although a relic honeycomb texture is retained. species rather than the radially elongate outline Like F. peripheroronda, the honeycomb texture of F. fohsi, its immediate predecessor. Fohsella is most strongly developed in the earlier cham robusta is a fully developed globorotalid, with an bers. In the final chamber or two, the wall may acute profile and a distinct keel bounding the be lacking visible ridges (Stainforth and others, peripheral margin. There is variation among 1975; fig. 117:3). The peripheral margin of F. populations, and some individuals may lack a keel peripheroacuta is either totally or partially perfo around the early chambers; but other individuals rate (Stainforth and others, 1975; fig. 117:1,4; have keels that extend around the entire test. Quilty, 1976, pi. 12: figs. 3, 4). A globorotalid The wall is smooth, but a strong development of feature introduced by F. peripheroacuta is the pustules sometimes conceals the primary surface. development of pustules around the apertural This form is totally comparable in architecture area (Stainforth and others, 1975, fig. 117:3). to the advanced forms of Globorotalia. Fohsella The succeeding forms, Fohsella praefohsi (Fig robusta evolved rapidly and has a limited strati ure 8f-g) and F. fohsi (Figure 8a-c) are very graphic range. It made its first appearance in similar to F. peripheroacuta, and these three spe Zone NI2, the same zone in which F. fohsi first cies have sometimes been grouped together as F. appeared, and became extinct in Zone N13. fohsi. The figures of Stainforth and others (1975) Using the scale of Ryan and others (1974) as a cited above as examples of F. peripheroacuta were reference, the estimated sequence of events (ap grouped with F. fohsi by those authors. The proximately in millions of years before present) globorotalid advancement shown by these suc in the evolution of Fohsella is as follows: ceeding forms is in the development of an im perforate peripheral rim and weak keel. There F. kugleri (first appearance) Zone N4 (base) 23 m.y. F. peripheroronda (first appearance) Zone N5 (middle) 21 seems to be no dispute that this development m.y. occurred sequentially; but the problem is that F. peripheroronda (last appearance) Zone N14 (lower) 12.5 development appears to have been rapid and m.y. with wide variation, so that the successive stages F. peripheroacuta (first appearance) Zone NIO (base) 15.5 can seldom be distinguished in stratigraphic se m.y. quences. F. praefohsi (first appearance) Zone Nl 1 (base) 15 m.y. F. robusta (first appearance) Zone N12 (middle) 14 m.y. Both Fohsella praefohsi and F. fohsi are about F. robusta (extinction) Zone N13 (early) 13 m.y. the same size as F. peripheroacuta with equiva- lently acute profiles and almost totally smooth While this scale can be used only as an approx walls. There is some increase in radial elongation imation, it does underscore the pattern of devel ofthe test, especially in F. fohsi. An imperforate opment, which was one of a long period of stasis rim is formed in F. praefohsi but is well developed and a short interval of rapid change. It took F only in the final chambers. The rim may be peripheroronda some 3 m.y. to evolve from F. accompanied by some weak keel formation, as kugleri, even though the architectural change suggested by the sectioned specimens of Blow amounted to very little. Another 5.5 m.y. elapsed and Banner (1966, pi. 2: figs. 6, 7). In F. fohsi a before F. peripheroacuta branched off from F. distinct rim extends around the entire test. peripheroronda. Here, a significant advance oc- NUMBER 58 19 curred, but it is possible that the transformation fully equivalent to that of Globorotalia, the F. was compressed within a short interval of time. robusta branch did not flourish and soon became The branching did not result in the complete extinct. Olsson (1972:183) attributed the devel replacement of the parental stock as F. peripher opment and extinction of the Fohsella robusta oronda survived in its original form for about branch to climatic causes. He correlated a maxi another three million years, somewhat longer mum size increase with the peak of a warming than the descendant lineage. Once branching cycle, and keel development and extinction with occurred, the advances in shell form were rapid, cooling at the end of the cycle. However, it is with the succeeding Fohsella species appearing at overly simple to view the oceans as a homoge intervals of about 0.5 m.y. The terminal Fohsella, neous entity that becomes equally warmed or F. robusta, survived for only slightly more than cooled in all places. In fact, the regional separa 0.5 m.y. The status of some of the short-lived tion of the Fohsella parental stock and its branch fohsellid taxa is uncertain. We have followed suggests that differentiation of watermasses oc current biostratigraphic usage but, as we note curred in the middle Miocene. Also, the devel later, several may represent arbitrarily defined opment of the menardines, a group strongly morphotypes within populations. preferring the tropics, occurred about the time In summary, Fohsella developed in the late of extinction of Fohsella, and so one would pre Oligocene-early Miocene from a coarse walled sume that suitable warm-water habitats were paragloborotalid, possibly like Paragloborotalia available. Indeed, competitive exclusion by G. ciperoensis. Some of the early development may menardii is a possibility. The increasing stenotopy have occurred through rapid speciation. How of the F. robusta branch may also be significant. ever, the actual transformation in shell design Cracraft (1982) suggested, for example, that probably did not occur through a quantum jump, stenotopy raises susceptibility to extinction. because Fohsella mendacis has intermediate paragloborotalid-globorotalid features. Once the Globorotalia zealandica Lineage basic globorotalid type of shell was achieved, there was a long period of stasis during which Although this is a minor lineage, with a short Fohsella was first represented by F. kugleri and history, it provides an interesting record of a then succeeded by the little modified, long-rang design that deviated from the main line of early ing F. peripheroronda. Throughout this time, Foh globorotalid development and presaged a later sella was cosmopolitan and showed no regional architectural trend. The early taxon, Globorotalia concentration in distribution that would suggest incognita, is differentiated from paragloborotal a watermass preference. In the middle Miocene ids like Paragloborotalia opima by several modest branching occurred, with a rapid (in a geologic but distinctive alterations of chamber shape. In sense) succession of populations developing along spiral view, chambers are elongated in the direc the branch that culminated in a fully developed, tion of coiling so that chamber length (coiling keeled globorotalid {F. robusta). With branching direction) exceeds height (radial direction). In P. occurred biogeographic partitioning, as the pa opima (Figure Ic) and allies the chamber margins rental F. peripheroronda retracted from the trop are semicircular, but in G. incognita they are ics, while the newly evolved species became in transformed to a broad, crescentic arch (Figure creasingly restricted to the tropics (Figure 34). 9^). The leading edge may show greater curva The seemingly anomalous occurrence of F. fohsi ture than the trailing edge, creating slight asym and F. lobata reported by Bartlett (1968) from metry in the margin. Convexity of the spiral Nova Scotia may be a reflection of Miocene surface of chambers (axial orientation) is weaker watermass structure (Cifelli, 1976a). than on the umbilical surface (Figure 9a). This Despite rapid development of a shell design produces a primitive version of the characteris- 20 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY tically flattened, or compressed, spiral surface of andica at a slightly earlier horizon and suggested globorotalid shells. Umbilically, chambers in the that it descended directly from P continuosa. On outer whorl are commonly slightly extended to the other hand, her figures of G. zealandica form a low, broad, convex surface without trace (Keller, 1981, pi. 3), do not compare well with of compression near the periphery. The umbili the New Zealand form (Figure 9g, h). They have cus is closed. The aperture is a high arch, some a fully ridged texture and chambers that are times like that in P. acrostoma, and greater than broadly radial, rather than elongate, in the direc in P. semivera. However, G. incognita retains the tion of coiling. These specimens offer no evi strongly ridged, honeycombed texture that char dence of G. zealandica development. acterizes the paragloborotalids. Evidence that the lineage was distributed The evolution of globorotalid chamber form wideiy around the southern oceans is indicated is advanced further in the succeeding species, by records of Globorotalia incognita from the Globorotalia zealandica (Figure 9c,d,f-h), which Southwest Atlantic (Tjalsma, 1977, DSDP Site appears in New Zealand at about Zone N6 (Hor 329) and G. zealandica from the Southeast Atlan nibrook, 1981b). The spiral margin is often less tic (Berggren and Amdurer, 1973, DSDP Site arched and some outlines are subquadrate. In 18; Jenkins, 1978, DSDP Site 360; Pujol, 1983, axial orientation, the central portion ofthe spiral DSDP Site 516). The specimen shown by Jenkins surface of late-formed chambers is nearly flat, (1978, pi. 1: fig. 19) may show the textural while the ventral surface is usually more strongly modification seen in Southwest Pacific popula raised than in G. incognita. The periphery varies tions. However, that the lineage was not re from subangular to broadly convex. In advanced corded from the lower Miocene sequence at specimens of G. zealandica both spiral and ventral DSDP Site 362 (Southeast Atlantic latitude 20 °S) components of chamber shape closely resemble by Jenkins (1978), or from Indo-Pacific se those in Pliocene G. crassaformis and G. puncti quences at similar latitudes (e.g., Shafik and culata. There is also some advance towards the Chaproniere, 1978), or from the equatorial smooth wall texture typical of the globorotalids. DSDP Site 289 (Srinivasan and Kennett, 1981b), Honeycombing is absent on the last-formed suggests that it primarily inhabited higher lati chamber, and the wall between pores has only tude water in the Southern Hemisphere, a view very low amplitude undulations. The penulti also advanced by Pujol (1983:628). mate and earlier chambers, however, retain mod There are several North Atlantic records, erately well-developed honeycomb texture. This again from higher latitudes. Specimens shown by tends to be strongest on chambers of the inner Poore (1979, pi. 7:figs. 10-12, DSDP Site 408, whorls, but chamber by chamber increments are 64°N) have the chamber form, textural, and not obvious. Shells from open ocean environ apertural features of Southwest Pacific popula ments may be encrusted. tions of Globorotalia zealandica, as does one of This history, based on temperate Southwest the specimens in Jenkins (1977, pi. 4: fig. 11, Pacific sequences, conflicts with that of Keller English Channel 49°N). King (1983:11) re (1981) who studied tropical and subtropical corded it from the North Sea and there is also a North Pacific sequences. She considered that tentative record of G. zealandica in Poore and Globorotalia incognita descended, via an inter Berggren (1975, DSDP Site 116, 57°N). None mediate, from Paragloborotalia continuosa, as ear of these works record the presence of both taxa. lier suggested by Walters (1965, fig. 5) and Jen There is an absence of records in the lower kins (1971:133), and recently reported by Srini Miocene of the Aquitaine Basin (e.g., Jenkins, vasan and Kennett (1981b:518), at about the 1966a; Poignant and Pujol, 1976). In the lower middle of Zone N4. In contrast to the New Miocene assemblages from southern Spain, Mol Zealand record, however, she identified G. zeal ina (1979) identified Paragloborotalia semivera, P NUMBER 58 21 nana, and related taxa as in the Southwest Pacific phylogenetic transformation rather than diver but did not find G. incognita or G. zealandica. gence. However, Tjalsma (1971, fig. 25) recorded G. In the perspective ofthe Neogene globorotalid zealandica from this region in higher faunas con radiation, this lineage represents an early exper taining Orbulina. This report draws attention to iment in the evolution of an inflated discoidal the need for further study of the later history of shell with only moderate advancement on the the lineage; The middle Miocene Globorotalia globular axial profile of the paragloborotalids. conica closely resembles G. zealandica, and South Spirally, chamber and shell shapes are as ad west Pacific records of the former (Jenkins, vanced as in later globorotalids (e.g., Globorotalia 1971:134) include one that was originally iden crassaformis) but, in G. zealandica, wall texture tified as G. zealandica by Hornibrook (1961:143). remained incompletely rectified. While the pe Possibly the lineage continued into the middle riphery of some late-formed chambers became Miocene. narrowly rounded (Figure 9d), advanced com The origin ofthe lineage involved only modest pression and keel development did not arise. changes to the chamber shape of the paraglo However, axial chamber shape may be significant borotalid ancestor. As yet, only Srinivasan and here as the later globose globorotalids (e.g., G. Kennett (198Ib:518) have reported connecting puncticulata, G. inflata, G. crassaformis) are simi populations (suptropical Southwest Pacific). larly keel-less. The lineage is thus distinguished However, it is premature to conclude that the from its two lower Miocene contemporaries by lineage arose in this region because of the possi its architectural direction towards ventrally in ble difficulty in distinguishing the slightly inno flated chambers rather than towards the com vative architecture of Globorotalia incognita in pressed biconvex design. The latter design large paragloborotalid assemblages (e.g., Molina, reached its acme in the middle Miocene whereas 1979). The character transformations in Globor globose designs, presaged by G. zealandica, arose otalia incognita that led to G. zealandica are afresh in the major Pliocene lineages. greater and better defined than those of the initial divergence. The New Zealand record in Globorotalia praescitula Plexus dicates that textural change and chamber rede sign occurred concurrently, although not neces Globorotalia praescitula is the stem species of sarily jointly on a particular individual, in a short the major component (in longevity, architectural stratigraphic interval. The distinguishing archi innovation, and taxonomic diversity) ofthe Neo tectural characters of G. zealandica occur only gene globorotalid radiation. Globorotalia praesci on chambers formed late in ontogeny. In some tula plexus is used here to include the main individuals, usually small, late-formed chambers descendants, as can be reasonably inferred from retain the shape of G. incognita. the stratigraphic records of intergrades and The evolutionary pattern suggested by the transformations of taxa. It refers to a minimally New Zealand record is step-like, in which two monophyletic group with limits that are some taxa of relatively stable morphology are linked, what arbitrarily defined. Thus, the plexus in in an ancestor-descendant sequence, by a brief cludes the widely divergent menardines because interval in which late ontogenetic innovations in the approximate time and mode of transforma form and texture occurred. Although there are tion in that group seem fairly clear, but excludes specimens in Globorotalia zealandica populations the scitulines, and the G. crassaformis plexus, that have not progressed beyond the G. incognita because their origins are still obscure. They are grade of evolution, there is no evidence of dis considered separately. Some taxa in the plexus tinct populations of the latter taxon after the have been placed in separate genera or subge appearance of G. zealandica. The record suggests nera by Steineck and Fleischer (1978) and Ken- 22 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY nett and Srinivasan (1983), but here we are con cerned primarily with tracing ancestry rather than with classification. Despite a certain amount of variability sug gesting a species group rather than a single spe cies, Globorotalia praescitula (Figure 10) retains a good degree of interregional identity and uni formity. Therefore, it seems appropriate to con sider it as a world-wide taxon from which later Globorotalia emerged. Globorotalia praescitula has been recorded from the tropical Atlantic region (Blow, 1959:221), the temperate North Atlantic (Poore, 1979:471), South Atlantic (Berggren and others, 1983:678), Mediterranean (Bizon and Glafon, 1978:691), the temperate North Pacific (Oda, 1977:60), and temperate Southwest Pacific (Walters, 1965:115). Srinivasan and Kennett (1981a:410-411) ap parently overlooked this cosmopolitant distribu tion when they restricted G. praescitula to a stem species of a tropical lineage leading to the men ardines and proposed G. incognita as the stem species of a temperate lineage leading to G. co noidea and descendants. Subsequently, however, Srinivasan and Kennett (1981b:518) and Ken nett and Srinivasan (1983:108) proposed that G. praescitula descended from the temperate G. zealandica and was ancestral to G. miozea. We consider that G. praescitula evolved independ ently ofthe G. zealandica lineage. It appeared in FIGURE 10.—Globorotalia praescitula Blow: a, BN141, base New Zealand prior to G. zealandica sensu stricto of section 6.75 km east of Ancona, Italy, lower Miocene (x and has more advanced wall topography. 170); b, Tocuyo Formation Eastern Falcon, Venezuela, par In its typical form from the Caribbean (Blow, atype (USNM 625714), lower Miocene (X 190); c, locality 1959:221), Globorotalia praescitula has a small, 309 (H.M. Bolli), Globigerinatella insueta Zone, Trinidad, lower Miocene (X 280); d, S136/f615, Oamaru, New Zea compact test with slightly more than four cham land, lower Miocene (X 230). bers in the peripheral whorl and a distinctly angular, but not acute, profile. In axial view (Figure \0b) the periphery appears blunted, and bean some ofthe early Miocene sequence is poor, the spiral side is just slightly convex. Wall relief obscuring the early development of G. praesci is low but there is a clear honeycomb texture in tula. According to the locality data given by Blow all but the final chambers. Pores are large and (1959:221) the holotype and paratypes come occur throughout the entire test. There is no from a horizon referable to Zone N7. Recent visible reduction in porosity at the peripheral examination of material from Trinidad has re margin. Chambers are elongate in the direction vealed an occurrence of this species in Zone N6 of coiling and are asymmetrical (B-type). The (type locality ofthe Catapsydrax stainforthi Zone). aperture is elongate and narrow. In the Carib- Berggren and others (1983) considered that it NUMBER 58 23 appeared near the base of Zone N7 in the South from the same zonal level. This basic form was Atlantic sequence at DSDP Site 516. retained by descendants; it was varied only in the The development of Globorotalia praescitula degree of compression at the periphery and in can be followed in the New Zealand early Mio the inclination of the ventral segment of the cene sequences where this species first appears at chamber wall. the base of the Altonian Stage (about Zone N6- Size Increase: Earliest individuals are small lower N7). Earliest representatives found in shelf (under 200 jtim diameter) with 4-4.5 chambers facies (Figure 6o,p) are sparse and small but in the outer whorl and a total of about 12 cham distinctly praescituline, except for a subspherical bers. Larger shells (over 400 um diameter) oc axial profile that deviates but little from the cur in later populations. Extension of ontogeny spherical profile of the paragloborotalids. Cham to include about 15 chambers occurred very bers are crescentic and distinctly elongated in the quickly, but the major mechanism of enlarge direction of coiling, representing a major trans ment was probably by increase in chamber formation from the slightly elongated chambers growth rates between the successive chambers. seen in some paragloborotalids, like Paraglobor Size increase possibly occurred gradually as a otalia bella. Another major transformation is seen phyletic trend. in the texture of the wall, which is nearly flat. A Texturally, New Zealand representatives of slight honeycomb texture is suggested, but it is Globorotalia praescitula made little progress to confined to the chambers of the early whorl. ward total reduction of wall topography. Ac Like the Caribbean types, New Zealand early tually, there is even an apparent slight reversal, representatives contain rather large, evenly as the earliest representatives are the smoothest. spaced pores, except in the final chamber where The only indications of honeycomb texture on pore size is reduced considerably. An apparent them are gentle undulations and low, broad difference, however, is that pore density tends to mounds around the pores of the inner whorls be reduced around the peripheral margin and (Figure 6o-p). In later Altonian populations, extends to the umbilical surface. This feature ridges constructed on the early whorls are remi persists in descendant forms. It is common but niscent of the honeycomb texture of the para variable in extent (Figures 6p, lOd). An imper globorotalids (Figure 6q,s). However, there is a forate band has not been observed on individuals conflict in the interpretation of these textures. from the Caribbean. According to one view (R.C), the undulations Two principal trends can be seen in the devel and ridges are actually vestigial traces of a par opment of Globorotalia praescitula in New Zea agloborotalid honeycombed texture. The fact land, where it is ubiquitous in middle shelf to that the wall in these early New Zealand forms is bathyal facies of the Altonian Stage. mostly flat shows that the transformation in tex Axial Profile: All populations show variation ture occurred neither in a single step nor through in profile, but the earliest ones (Figure 6p) tend a progressive series of changes. During the trans to be subspherical and lack the angularity of formation, the regulatory balance between ridge- typical globorotalids. In later forms from the forming and sheet-like calcification included a Altonian Stage (Zones N6-N7), most outlines are period of instability so that relic honeycombed considerably more compressed. At this stage the textures were retained to a greater extent in spiral side is weakly convex and runs into a sector some populations than in others. The paratype of rapid curvature at the periphery. The umbil of G. praescitula has a rather coarse, ridged tex ical side inclines downward towards the coiling ture (Figure lOb) that provides a good link with axis and often is partly linear. This results in a a paragloborotalid ancestor, even though it may subangular to angular profile that compares fa be younger (in Zone N7) than the New Zealand vorably with the profiles of the Caribbean forms forms. According to another view (G.H.S.), the 24 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY undulations and ridges on the early New Zealand large and evenly distributed. However, as in New forms (Figure 65) may be no more than simula Zealand, there is a tendency towards imperfora- tions of ridged, honeycombed textures and may tion or semiperforation around the peripheral not necessarily be a paragloborotalid relic. Their margin and adjacent umbilical region. This absence entirely from some of the earliest speci tendency persists in descendant forms. There mens, and from late-formed chambers of more is no difference in wall texture between early advanced specimens, support this interpretation. and later Mediterranean populations. The prin Furthermore, the constructional ridges often cipal change from early to later populations of fuse together over the earliest chambers (Figure Mediterranean G. praescitula involves, as in New 6s), a feature not seen in Paragloborotalia. Zealand, the extent of compression at the cham In the Mediterranean, developmental trends ber periphery. This results in an acute profile in Globorotalia praescitula are similar to those in (Bizon and Glafon, 1978, pi. 1,2). There also New Zealand, although comparison is somewhat appears to be some increase in size of the test complicated by a "timing" problem. Planktonic between early and later populations. foraminiferal markers for a biostratigraphic framework are lacking at the DSDP core Site NEW ZEALAND RECORD OF 372 where the early Mediterranean occurrences GLOBOROTALIA MIOZEA of G. praescitula are recorded (Bizon and Glagon, 1978). Globorotalia praescitula first appears in the A useful perspective on the development of upper part of the Sphenolithis belemnos Zone Globorotalia miozea, which we consider to be the (NN3), which is about equivalent to the base of descendant of G. praescitula, is available in New the planktonic foraminiferal Zone N7. There Zealand, the region from which that species was fore, G. praescitula possibly appeared later in the first described. The taxa show a gradational re Mediterranean than in the Caribbean or New lationship. Hornibrook (1961:144) noted the Zealand where records extend down into Zone larger size of G. miozea (he identified G. praesci N6. tula as "G. miozea small variety"), but discrimi As elsewhere, the Mediterranean appearance nation solely on this basis would be arbitrary. of Globorotalia praescitula is cryptic and cannot However, populations of the upper Altonian be connected in a gradational series with an Stage (about Zone N7) exhibit several other ancestor. Even the earliest forms have distinctly changes which, either singly or in combination, elongated chambers in the direction of coiling are more useful in identifying the appearance of and, like New Zealand representatives, are sym G. miozea. The transformations are neither ab metrically crescentic. However, in later popula rupt nor necessarily concurrent: (1) Chambers tions chamber shape changes from symmetric to became more compressed at the periphery (Fig asymmetrical (Bizon and Glafon, 1978, pi. 1,2). ure 6k,m) and the profile sometimes became an Profiles are variable and early populations in gular, particularly in crust-free specimens; there clude some that tend to be subspherical, although was a tendency towards umbilical elevation of they are generally subangular and compare more the axial profile, a tendency that was continued favorably with the Caribbean profiles than the in some descendants of G. miozea. (2) Not strictly ones in early New Zealand populations. The spi architectural but nonetheless important, was the ral sides of the Mediterranean forms are flat to initiation of crust formation, a feature that is convex. Convexity is found not only in early particularly characteristic of Southwest Pacific populations but in later ones as well. Wall surface populations. (3) A change in coiling direction is low, comparing favorably with the New Zea occurred (Walters, 1965, fig. 4; Jenkins, 1971, land forms, but a relic honeycomb texture is table 58); sinistrally coiled shells became domi visible in most of the chambers. Pores are rather nant in the upper Altonian Stage and this mode NUMBER 58 25 remained dominant in Miocene descendants. (4) discriminate the weak ridges formed on the ear The number of chambers in the outer whorl liest keeled specimens. At this stage, the keel is increased, with some individuals having five; B- more obvious on the spiral side of the peripheral type spiral chamber outlines (Figure 6) became margin. However, the amplitude of the fold in typical. creases and, in populations associated with the Of the above changes, the increased chamber appearance of Orbulina universa (in Zone N9), compression resulting in an acute profile was the some cord-like structures occur. We use the de most significant, as it marked the inception of velopment of a keel to mark the appearance of the evolution of the keel, the culminating archi the G. praemenardii morphotype. Specimens fig tectural structure in Globorotalia development. ured as G. miozea by Kennett and Srinivasan The earliest stage in the evolution of the keel (1983, pi. 26: figs 1-3) are at this stage (compare detectable in New Zealand representatives of G. with topotypes in Figure 6j-n). miozea is the presence of a narrow, translucent The axial shape of Globorotalia miozea is com rim at the angular periphery of compressed monly biconvex but there is wide variation. chambers. Under reflected light it appears con Chambers in some individuals extend umbili tiguous with the intercameral suture and is made cally, presaging the architecture that became typ distinct by its highly reduced pore density (Scott, ical of G. conoidea populations. Other shells, often 1973a, pi. 2: figs. 8,9). It has no topographic crust free, show less umbilical extension (Walters, expression and cannot be distinguished by scan 1965, fig. 8f-h), and a few have flat or even ning electron microscopy. This rim is compara slightly concave umbilical surfaces as in G. panda. ble to the one seen in Fohsella fohsi and represents Compression of chamber peripheries is also a comparable stage in keel development. The widely variable but tends to be correlated with structure is most obvious on the latest chambers the axial form of the shell. It is weakest in um but commonly extends back to those formed in bilically extended chambers and strongest in mid-ontogeny. In New Zealand, a rim first ap those with relatively flat umbilical surfaces. Usu pears in G. miozea populations near the entry of ally, there are about five chambers in the outer Praeorbulina or early in Zone N8. Initially, all whorl with six-chambered variants occasionally gradations from absence to clear definition of present. These variants tend to be large with the structure occur, possibly depending on the wide, radially extended chambers and raised angularity of the junction between spiral and trailing edges (advanced B-type form). umbilical walls. The interval between the appearances of ENCRUSTATION Praeorbulina glomerosa curva and Orbulina sutur alis (Zone N8), corresponds with the period in In New Zealand, the first occurrence of Glo which rim formation spread in Globorotalia borotalia miozea often equates with the onset of miozea populations to become a common char encrustation. Indeed, the earliest representatives acter of the species; the type population is from of G. miozea are little more than rather large, this interval. Concurrently, a primitive keel ap encrusted counterparts of G. praescitula and ap peared, recognizable as a distinctive topographic pear in the Altonian Stage. Thereafter, encrus feature at the peripheral margin. The keel de tation is a characteristic feature of New Zealand velops as a fold or a crimp in the chamber wall G. miozea and its descendants. While onset of at the junction ofthe umbilical and spiral surfaces encrustation helps to define the first occurrence (Scott, 1973a, pi. 2: figs. 1-4), forming a cord of G. miozea, it did not coincide with any major like structure. As with the origin ofthe rim, keel change in shell design. It possibly arose late in a formation was initially weak and variable (Figure phase of chronoclinal increase in size, and it 6f,i). Scanning electron microscopy is needed to could be argued just as easily that encrustation 26 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY originated in the late stages of G. praescitula. regions (Cifelli, 1982). Of course, this evidence Encrustation is a highly variable phenomenon in does not completely negate a bathymetric and/ G. miozea and cannot be used as a governing or cool water control of encrustation because it taxonomic criterion. New Zealand populations is possible that, in towing down to 200 m, the of G. miozea commonly contain crust-free as well critical depth had been passed and the encrusted as heavily encrusted specimens, with ratios be specimens were recovered in the lower depth tween the morphotypes and the amount of en range. On the other hand. Be (1980:294) found crustation varying considerably. Nor can the that laboratory cultured specimens of G. sacculi- crusted and uncrusted forms be separated satis fer became calcified during gametogenesis, factorily by other morphologic criteria. Jenkins where neither depth nor temperature was a fac (1971, table 38: sample 651) referred small un tor. crusted specimens to G. praescitula, large un This review could be pursued at length, but crusted specimens to G. praemenardii, and en there would be no advantage, as a satisfactory crusted ones to G. miozea. All are probably intra- conclusion cannot be reached at present. Un populational variants, not easily discriminated questionably, encrustation occurs ontogeneti- except for size and incidence of crust. We do not cally, but the relationship of this phenomenon consider such reports as evidence of speciation with the environment, or with life processes, in G. praescitula. remains unclear. Probably no single generaliza The evolution of the crust is an interesting tion can be made and individual species may have problem, as yet unresolved. At least initially, their own peculiar habits. Certainly, the devel crusted forms of G. miozea tended to be larger opment of crust in Southwest Pacific populations than crust-free ones, which suggests that an on of G. miozea and its long persistence in descen togenetic factor is involved, while the very nature dants is a rather unique historic feature among of the phenomenon seems to call for some envi planktonic foraminifera. Following the model of ronmental explanation, such as bathymetry and/ Hart (1980), this development in G. miozea pos or temperature. That bathymetry was a control sibly resulted from colonization of the lower is implied by the fact that encrusted specimens depths for part of its ontogeny during the early do not occur in shallow shelf, inshore Altonian Miocene when that section of the water column facies. Whether a bathymetric explanation can provided a vacant niche. Migration could have be upheld by analogy with the distribution of been induced by the increase in size and ex modern planktonic species remains unclear. Ken tended ontogeny of G. miozea over its praescitu nett (1976) reviewed the problem and, while he line ancestor. The first invasions may have oc concluded that encrustation was an ontogenetic curred fortuitously as "buoyancy costs" arising feature associated with deeper and/or colder wa from the evolution of large shells. Such an expla ter, the evidence remains equivocal. For exam nation, of course, would have to allow that mi ple, Hecht and Savin (1970) studied the oxygen gration to lower depths did not occur uniformly composition ofthe crust and entire shell of Sphae throughout the oceans, because in the tropics roidinella dehiscens and found that crust regis encrusted forms are scarce. However, it is not tered a warmer temperature than the whole possible to arrive at a good estimate of the rela shell. Their conclusions were challenged by Be tive importance of encrusted versus crusted and van Donk (1971). In the water column, forms in various regions from published ac encrusted forms of the subtropical species Globi counts, because encrustation has sometimes been gerinoides conglobatus are commonly captured in used as the principal criterion for identification. oblique plankton tows from 0-200 m, while en Uncrusted counterparts have sometimes been crusted forms of Neogloboquadrina dutertrei are referred to as unkeeled forms of G. praemenardii recovered from similar types of tows in tropical (e.g., Jenkins, 1971). NUMBER 58 27 NORTHERN REPRESENTATIVES OF very similar. The holotype of G. praemenardii has GLOBOROTALIA MIOZEA a weak keel that extends around the entire shell (Blow, 1969, pi. 6: figs. 1-3), but, as in New A major question at this point is whether Glo Zealand, populations are variable and include borotalia praescitula was succeeded by world-wide rimmed or even unrimmed forms as well. Blow populations referable to G. miozea or whether G. (1969:368) noted that G. praemenardii has a more praescitula was followed by divergent tropical depressed shell than G. archeomenardii and a and temperate lineages. We have previously more circular spiral outline (compare Figure 11/ noted that Srinivasan and Kennett (1981a, with Figure 1 Ik). He thought that the two forms 1981b) proposed inconsistent views about this could often be distinguished in this way. But such question. The issue involves matters of taxonomy separation can sometimes be difficult (compare and levels of variation considered allowable. Cer Figure lla with Figure llo). Blow (1969:369) tainly, what divergence may have occurred recognized a transition between G. archeomenar amounted to very little, because the developmen dii and G. praemenardii at about the boundary tal trends in the tropics following G. praescitula between Zones N9 and NIO. closely parallel those in the temperate Southwest Forms transitional between Globorotalia prae Pacific. Also, while the pace in development may scitula and G. archeomenardii occur in the Carib not have been identical, changes occurred at bean about the level of Zone N8, which is some about the same time. The developmental trends what higher than the time of transition from G. involve profile changes that lead to the formation praescitula to G. miozea as identified in New Zea of a keel. At the partially keeled stage, Caribbean land. Earlier, Scott (1972) referred a Zone N8 populations of G. praemenardii are not clearly Caribbean population to G. praescitula with separable morphologically from New Zealand which it shows close affinity in its totally perfo populations of G. miozea and a two-lineage hy rate profile. However, advancement is shown by pothesis was not upheld by Scott (1972). Whereas strong compression and acuteness of the profile, Kennett and Srinivasan (1983) envisaged a trop which appears more developed than in the New ical-temperate divergence in G. praescitula pop Zealand forms of G. miozea. In the G. barisanensis ulations, we locate the major branch in the plexus Zone of Bolli, or Zone N9, rims and some partial later, between G. conoidea (fully keeled B-type keels appear on G. archeomenardii, which is about chambers, moderately elevated on the umbilical contemporaneous with the development of these side) and G. menardii (fully keeled C-type cham features on G. miozea in New Zealand. Through bers and compressed, discoidal shell). out the development of G. praescitula-G. archeo- In the Caribbean, Globorotalia praescitula is menardii-G. praemenardii the pores remain large. succeeded by a form that Bolli (1957) called G. The major differences in development be archeomenardii (Figure ll^-o,r-^). It is a small tween the Caribbean and Southwest Pacific pop form, little larger than G. praescitula, with a very ulations involve size and encrustation. In the acute profile that usually has a rim around the Southwest Pacific populations size increase is ev peripheral margin and, sometimes, even a partial ident by Zone N8, but in the Caribbean an in keel. In his description, Bolli (1957:120) men crease does not occur until Zones NIO-Nll. tioned that G. archeomenardii has a convex spiral Populations showing size increase in the Carib side, but the taxonomic importance of that fea bean are the ones that have been referred to ture should not be overemphasized. It is common Globorotalia praemenardii, while the older, (Figure 1 Ir), but many individuals do not show smaller forms have been referred to G. archeo it at all. Globorotalia archeomenardii in turn is menardii {e.g., Blow, 1969). Globorotalia praemen succeeded by G. praemenardii (Figure lla-j), ardii populations do show an advancement in which is an appreciably larger form but otherwise keel development, but the keel is weak and not FIGURE 1 1.—a-j, Globorotalia praemenardii Cushman and Stainforth {a,b, type locality Fohsella robusta Zone, Trinidad, middle Miocene (X 105); c-e, cotype locality F. fohsi Zone, Trinidad, middle Miocene (X 100);/, locality 13 (P.W. Jarvis), Lower Green Clay, Cipero Section, Trinidad, middle Miocene (X 90); g, locality GG20379 (BMNH), Santo Domingo, middle Miocene (X 125); h-j, type locality F. lobata Zone, Trinidad, middle Miocene (X 80)); k-o,r-t, Globorotalia archeomenardii Bolli {k,l, locality 12 (P.W. Jarvis), Upper Marl, Cipero Section, Trinidad, middle Miocene (X 160); m-o,r-t, type locality F. peripheroronda Zone, Trinidad, middle Miocene {m-o, X 145; r-t, X 150)); p,q, Globorotalia praescitula Blow, Tocuyo Formation Eastern Falcon, Venezuela, paratype (USNM 625714), lower Miocene (X 170)). NUMBER 58 29 much better defined than the rim of G. archeo quence. However, the succession of forms in the menardii. The available evidence suggests that G. Gaudalquivar Basin of southern Spain that archeomenardii populations are smaller in size Tjalsma (1971:57) referred to as Globorotalia than G. miozea while G. praemenardii is fully menardii forms 1-5, are relevant. The earliest of comparable to the latter. Encrustation is mostly these forms, G. menardii form 1, is comparable lacking in the Caribbean populations but, as dis to advanced G. praescitula or early G. miozea (4.5- cussed before, this is a variable feature in the 5 chambers in the outer whorl). It has chambers Southwest Pacific populations and is of dubious elongate in the direction of coiling and a profile taxonomic value. that is subangular, but not acute. There is no In the North Atlantic, morphotypes of Globor indication of a peripheral rim. The succeeding otalia miozea (Poore, 1979, pi. 6: fig. 12) and of G. menardii form 2 is clearly more advanced and G. praemenardii (Poore and Berggren, 1975, pi. compares well with G. archeomenardii. This form 1: figs. 4-6) occur together through Zones Nl 1- has a distinctly acute profile. Some specimens N13 (approximately), a distribution resembling (e.g., Tjalsma, 1971, pi. 4: fig. 5c) are without a that in the Southwest Pacific. keel, while it is weakly developed on others In the Mediterranean, a similar developmental (Tjalsma, 1971, pi. 4: fig. Ab). Tjalsma's Globor trend leading from the primitive Globorotalia otalia forms 3-5, are fully keeled forms and will praescitula to G. miozea with rims and partially be considered later. The Mediterranean region formed keels occurs at DSDP Site 372 (Bizon is in need of more sampling and study. and Glafon, 1978). Forms transitional between G. praescitula and G. miozea, or primitive G. ar SUMMARY OF THE EARLY HISTORY OF THE cheomenardii, occur in association with Praeorbu PLEXUS lina glomerosa or at a level equivalent to Zone N8. These forms, referred to as G. archeomenar We suggest that the same developmental stages dii (Bizon and Glafon, 1978, pi. 3: fig. 7), have in the evolution of the axial profile and keel a very acute profile, like the Caribbean forms, (Figures ?>e-g, 4) can be followed in sequences and a peripheral margin that is partially im.per- from the Southwest Pacific, Caribbean, and Med forate and even slightly rimmed. They tend to iterranean regions and that they occurred at be somewhat larger than G. praescitula and are approximately equivalent horizons. There was a succeeded by still larger forms that have distinct world-wide, progressive trend in the evolution of rims and partially formed keels. Bizon and Gla- Globorotalia during the early to middle Miocene, fon (1978) referred some of these forms to G. despite some regional differences in size, shape, magnifica, a spiroconvex species that shows close and encrustation. Importantly, the same, pro relationship with G. panda. However, some in gressive development in profile and keel can be dividuals figured by Bizon and Glaf on are clearly followed at both tropical and temperate latitudes. biconvex and of the same evolutionary grade as Because development was so cosmopolitan, we G. praemenardii (Bizon and Glafon, 1978, pi. 4: think that the single lineage concept for the fig. 5). Encrusted forms of G. miozea were iden evolution of Globorotalia is better supported than tified from the same core section. Partially keeled that of parallel tropical and temperate lines of forms referable to G. praemenardii are well rep descent (Kennett and Srinivasan, 1983:103, resented at levels equivalent to Zone N12. As in 120). Furthermore, in each region there is a the Southwest Pacific and the Caribbean, these common pattern of gradual transformation, sub forms are not readily separable from an unkeeled stantial intrapopulation variation, and intergra- G. miozea population. dation. Surface outcrops ofthe lower and middle Mio The taxonomy ofthe lineage is currently in an cene in the Mediterranean region are inade unsatisfactory state because of synonymies aris quately exposed to establish a developmental se ing from studies of contemporaneous popula- 30 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY tions in different regions, wide local variation, In the Neogene radiation, spiral convexity first and the rather inconspicuous, gradual evolution developed in the Globorotalia praescitula plexus of the keel. Blow and Banner (1966) used the during the middle Miocene (Figure 12<2-^), sub stages in development of profile and keel for the sequently redeveloped at about the beginning of subdivision ofthe Fohsella lineage and we suggest the Pliocene in G. margaritae (Figure 12h-j) and, that this method might also provide a workable still later, appeared occasionally in populations taxonomy of the Globorotalia praescitula lineage, of G. cultrata (Figure 12^-/). Architecturally, as follows. these forms are very close, but the stratigraphic Globorotalia praescitula: rounded periphery, record indicates that they are products of con rimless; 4-4.5 A- or B-type chambers in outer vergent trends. whorl. When they first appear in the middle Miocene, Globorotalia miozea: moderately compressed spiroconical shells are closely associated with pop periphery, usually rimmed, rarely with very weak ulations of Globorotalia miozea and G. praemen keel; 4.5-5 chambers in outer whorl; chambers ardii. Globorotalia panda was named from the of the B-type. Globorotalia archeomenardii may Southwest Pacific and G. magnifica from the warrant recognition as a smaller, more com Mediterranean, but both show similar patterns pressed, regional subspecies. of variation; we tentatively regard them as a Globorotalia praemenardii: compressed, angu single branch of the G. praescitula plexus. lar periphery, usually rimmed and often with a Earliest spiroconical forms (about Zone N12) weak keel on late-formed chambers; about five from New Zealand, referred to Globorotalia B-type chambers in outer whorl. Such specimens panda by Jenkins (1971:97), display moderate to have been previously identified in New Zealand strong spiral convexity, but the ventral surfaces as G. miozea. Careful inspection by scanning mi are commonly slightly raised rather than de croscopy may be required to determine the pres pressed (Figure 12^). The periphery tends to be ence of a keel. more strongly compressed than in the contem It should be stressed that all of the morpho porary G. praemenardii and the keel is more types, as defined above, may occur in individual prominent. However, most characters intergrade assemblages at about Zones N9-N12. The value with those of G. praemenardii, and it is only the of identification by major morphotype, as op combination of spiral convexity and well-formed posed to the mere presence of an advanced form, keel in a few individuals that allows recognition needs to be assessed. of G. panda. The record therefore suggests a morphotype within the main G. miozea-G. prae EARLY SPIRALLY CONVEX FORMS menardii populations rather than a separate spe Most globorotalid shells are either biconvex or cies or even a subspecies. more convex on the umbilical side than the spiral Later (about Zones N14-N16), populations of side. Individuals in which the spiral side is more Globorotalia panda can be recognized in New convex than the umbilical are more often the Zealand that are clearly differentiated from G. exception rather than the rule. Forms with a very conoidea and G. menardii. The periphery is acute rapid translation of whorls along the coiling axis, and bounded by a prominent, thick keel. Spirally, such as the benthonic Patellina corrugata or the chamber shape resembles the B-type but is gen planktonic Globigerinita bradyi did not develop erally more elongate, as in G. margaritae (com out of the basic globorotalid architecture. The pare Figures 6, I2a,i). In some specimens spiro closest globorotalid form is Globotruncana con- conical shape is accentuated by a depressed, or tusa from the Cretaceous radiation. Among mod flat, ventral surface (Figure 12*). Similar shells ern Globorotalia, only G. hirsuta is spirally con occur in the Southeast Atlantic (Jenkins, 1978, vex. pi. 2: figs. 3-5). NUMBER 58 31 FIGURE 12.—a-d, Globorotalia panda Jenkins {a-c, Y18/f92, Gisborne, New Zealand, upper Miocene {a,b, X 100; c, X 195); d, N80/fl405, Mata River, New Zealand, middle Miocene (X 110)); e, Globorotalia archeomenardii Bolli, type locality Fohsella peripheroronda Zone, Trinidad, middle Miocene (X 145);/,^-, Globorotalia hirsuta (d'Orbigny), DSDP Site 284, 1-1-35, Southwest Pacific, Quaternary (X 45); h-j, Globorotalia margaritae Bolli and Bermudez, Chain Station 115- 6-67, South Atlantic, Pliocence (A, 346 cm, X 195; i, 346 cm, X 80;;, 323 cm, X 95); k,l, Globorotalia cultrata gibberula Be, locality RC 9-150 (surface sediment), Indian Ocean, Recent (X 45); m-o, Globorotalia aff. margaritae Bolli and Bermudez, Chain Station 115-6-67, 507 cm, South Atlantic, upper Miocene {m,n, X 90; o, X 95). While many Trinidad individuals of Globoro fails to develop to any significant degree. There talia archeomenardii have a moderately convex is no subsequent record of morphotypes like G. spiral surface (Figure 12^; Bolli, 1957, pi. 28: fig. panda in that region and, indeed, Caribbean 11; Blow, 1969, pi. 47: figs. 1-4), this feature populations of G. praemenardii tend to be less 32 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY convex, spirally, than the preceding G. archeo flaring, C-type chambers, increased axial com menardii (Figure 11). pression, and a reduction in pore size. The bifur The Mediterranean record of spiroconical cation is accompanied by the first biogeographic forms is more comparable with that ofthe South differentiation in the plexus, as G. menardii de west Pacific. Bizon and Glagon (1978) proposed veloped in the tropics and all of its descendants Globorotalia magnifica for a spirally convex form continued to show a strong preference for that with a distinct keel and they noted similarities habitat (Figure 35). Globorotalia conoidea and its with G. panda and G. praemenardii. Their illus successors tended to avoid the lower latitudes trations show only a moderate development in and are characteristic of subtropical and temper spiral height, ventral depression and keel, which ate regions (Srinivasan and Kennett, 1981b). suggests that G. magnifica is closer in affinity to However, there is considerable overlap in the early forms of G. panda (Figure I2d) than to distribution of these two groups, particularly in later, fully developed forms (Figure I2a,b). Some the northern hemisphere. weak-keeled specimens of G. magnifica (e.g., Bi zon and Glafon, 1978, pi. 4: fig. 5) compare with THE CONSERVATIVE BRANCH, ones from New Zealand identified as G. praemen GLOBOROTALIA CONOIDEA ardii (Figure 6a,b). The range attributed to G. The origin of Globorotalia conoidea involved magnifica (about Zones N10-N12) further sug neither rapid character transformations nor in gests that this form refers to an early segment of troduction of novel structures. Fixation of keel the G. panda branch. Globorotalia ichinosekiensis, construction in late ontogeny is the major evo described by Takayanagi and others (1976) from lutionary advance of this species over G. praemen strata of about Zone N14 age in Japan is possibly ardii. Walters (1965) distinguished G. conoidea a synonym of G. panda. from G. miozea (in which he included specimens While further work on the middle Miocene we regard as G. praemenardii) by its larger size spiroconical forms is needed, present records and high umbilical side, as well as by the presence indicate a gradational and perhaps rather grad of a distinct keel. However, in New Zealand there ual divergence from Globorotalia praemenardii is no consistent size difference, and individuals populations. In both hemispheres the distribu with vaulted umbilical surfaces occur in both G. tion was extratropical. In New Zealand and ad miozea and G. praemenardii populations. The jacent deep sea sites (Srinivasan and Kennett, New Zealand record shows that G. conoidea pre 1981b, figs. 4, 5) the extinction of G. panda served much of the variation spectrum of G. occurred in Zone N16, significantly before the miozea and G. praemenardii except for the fixa entry of G. margaritae. tion of the keel (Scott, 1975). Architecturally minor, but significant, changes were reductions GLOBOROTALIA CONOIDEA- GLOBOROTALIA in the convexity ofthe spiral surface of chambers, MENARDII DIVERGENCE in the depression of sutures, and in offset be The appearances of Globorotalia conoidea and tween chambers. While some early populations G. menardii mark the separation of Globorotalia of G. conoidea are strongly conical, ventrally bio- praescitula plexus into two distinct lineages. It is convex shells persisted. Some populations from a major divergence (Figure 2). Both species are northeastern New Zealand also include large, fully keeled and represent culminations of the disk-like forms. Walters (1965) treated popula globorotalid architectural form. Globorotalia co tions of biconvex forms as G. miozea sensu lato, noidea remained close to the parental stock and while Jenkins (1971, pi. 6: fig. 138) identified is hardly more than a fully keeled G. praemenar crust-free biconvex specimens like that in Figure dii, with a tendency towards vaulting on the 13n-o as G. miotumida. Both are here regarded ventral side. Globorotalia menardii underwent a as variants of G. conoidea. While the umbilical change in shell design by the development of surfaces of G. conoidea are, on the whole, clearly FIGURE 13.—a-c, Globorotalia pliozea Hornibrook {a, DSDP Site 284, 14-4-20, Southwest Pacific, Pliocene (X 70); b-c, DSDP Site 284, 14-6-20, Southwest Pacific, Pliocene {b, X 80; c, X 70)); d-g Globorotalia mons Hornibrook {d,e, DSDP Site 284, 15-6-20, Southwest Pacific, topotype. Pliocene (X 65); f,g, DSDP Site 284, 16-3-20, Southwest Pacific, upper Miocene (X 85)); h-r, Globorotalia conoidea Walters {h-j, DSDP Site 284, 16-3-20, Southwest Pacific, upper Miocene {h, X 80; i, X 100; j, X 80) {h represents the ventrally elevated morphotype described as G. conomiozea by Kennett, 1966; k-o, N98/f 565, Waimata River, New Zealand, topotypes, middle Miocene k,l, X 100; m X 105; n,o, X 100); p-r, cotype locality Paragloborotalia mayeri zone, Trinidad ("form 3" morphotype of Tjalsma, 1971, middle Miocene, p,q X 95; r X 105)), s,t, Globorotalia mediterranea Catalano and Sprovieri, JTl911 A, Falconara, Sicily, upper Mio cene (X 75). 34 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY more vaulted than in G. miozea, the axial shape ocene descendants of Globorotalia conoidea are oscillated within wide limits. Late in the history widely distributed in the temperate regions of of G. conoidea in the Southwest Pacific (about the Southern Hemisphere. Scott (1983) recorded Zone N17), there was an acme of highly conical, them from the South Atlantic Rio Grande Rise. quasitruncatuline forms. Kennett (1966) pro G. pliozea, at least, seems to occur in the Indian posed G. conomiozea for these (Figure 13/i) but, Ocean (Boltovskoy, 1974: pi. 11: figs. 8,15,17; commonly, gradation in degree of ventral eleva recorded as G. conoidea). Globorotalia conomiozea tion with G. conoidea forms occurs within a single subconomiozea Bandy, described from Pliocene assemblage, and we do not think that G. cono sediments in a submarine core, may be a very miozea is specifically separable. Vincent close relative of G. pliozea. The Pliocene speci (1981:345) has a similar view. Records from the mens from North Pacific DSDP Site 310, illus Southwest Atlantic (Pujol, 1983, Table 4, DSDP trated by Keller (1978, pi. 1: figs. I-IO) as Glo Site 516) of G. conomiozea almost always associ borotalia conomiozea and G. conoidea, may resem ated with G. conoidea in consecutive samples over ble G. mons. The extinction of G. pliozea in the a substantial interval in the upper Miocene may upper Pliocene appears to close the record of the indicate intraspecific variation. G. conoidea group in the Southern Hemisphere. The number of chambers in the outer whorl The relationships of species recorded from the also fluctuated in the history of Globorotalia co Mediterranean region as Globorotalia menardii noidea. In recollections from the type locality, an form 3, G. dalii, G. mediterranea, and G. cono early horizon (about Zone N14), 4-4.5 cham miozea are uncertain. A close relationship with G. bered forms are dominant. In later populations conoidea is indicated by the retention in these five-chambered forms are dominant, and some species of a shell design like those of G. miozea individuals have six chambers; similar variation and G. praemenardii, with elongate, B-type cham occurred in G. miozea. However, late in the spe bers and large pores (Figure l'6p-t). However, cies history, the number of chambers declined there are some regional differences between the progressively and the four-chambered form development of the Mediterranean and South again became predominant. This trend in reduc west Pacific populations. The earliest of the tion is associated with the acme of the highly above Mediterranean species, G. menardii form conical G. conomiozea variants and probably oc 3, like G. conoidea, is hardly more than a strongly curred throughout the southern oceans. There keeled G. praemenardii. In the Mediterranean, it is evidence of it in the South Atlantic (Scott, immediately succeeds G. praemenardii at a level 1983) and the Southwest Pacific (Malmgren and equivalent to Zone N13 where it occurs side by Kennett, 1981). side with G. menardii (Bizon and Glagon, 1978). In the Pliocene, variation in the ventral eleva Globorotalia menardii form 3 also occurs at about tion of shells appears to be much more bimodal the same level, and alongside G. menardii, in the among Southern Hemisphere populations than Caribbean (Cifelli and Glagon, in press). Globor the late Miocene ones. Globorotalia mons (Figure otalia menardii form 3 probably can be regarded I2>d-g) is strongly ventroconical, while G. pliozea as an infra-specific form of G. conoidea. The only (Figure 13fl-c) retains the convex shape of many apparent difference is that G. menardii form 3 of the earlier G. conoidea populations. In both tends to have a narrrowly biconvex rather than species, the umbilicus is narrower and the aper a vaulted profile. However, Zachariasse ture lower than in the preceding populations of (1975:101) noted that this species may also have G. conoidea, including the truncatuline, cono a moderately convex umbilical side (Zachariasse, miozea, form. In G. pliozea, an elongate, A-type 1975, pi. 2: fig. bb). Distinctly vaulted forms chamber is typical and, like G. mons, four cham have not been recorded from the Caribbean or bers are included in the outer whorl. The Pli other tropical regions. NUMBER 58 35 It is more difficult to establish the possible taxa associated with G. conoidea as follows. relationships of the later occurring Globorotalia Globorotalia miotumida: crust-free variants in dalii and G. mediterranea (Figures I3s,t, llfg), Southern Hemisphere; possibly a senior synonym which do not appear in the Mediterranean until of G. conoidea. Zone N17. Both species show a distinct vaulting Globorotalia menardii form 3 of Tjalsma: in- ofthe umbilical side, and the more vaulted forms fraspecific variant, usually more compressed than of G. mediterranea have been assigned to G. con Southern Hemisphere form of G. conoidea. omiozea by Mediterranean workers (e.g., Zachar Globorotalia dalii, G. mediterranea, G. conom iasse, 1975:105; D'Onofrio and others, 1976, pi. iozea (of Mediterranean usage): closely interre 4: figs. 1,2). However, Scott (1980b) noted that lated forms, varying primarily in axial shape; none ofthe Mediterranean populations show the greater similarity with G. menardii form 3 and same developmental trends as the New Zealand early southern populations of G. conoidea than populations of G. conoidea. The Mediterranean with uppermost Miocene populations in the latter forms, while distinctly vaulted, are always domed region. and never conical as in the quasitruncatuline Globorotalia iwaiensis: possibly a synonym of G. conomiozea morphotype. Also, the Mediterranean conoidea. populations do not show the reduction to four Globorotalia miozea rifensis: synonym of G. co chambers in the outer whorl (Figure 39) that noidea; fully developed keel; probably the equiv characterizes the later populations of G. conoidea alent of G. menardii form 3 of Tjalsma. in New Zealand. Globorotalia saheliana (Figure Globorotalia saphoae: greater ventral elevation lla,b) may be related to these keeled Mediter of chambers than on other Mediterranean mor ranean populations. Catalano and Sprovieri photypes; very closely resembles southern G. co (1971:241) described the keel as weak and lim noidea (e.g.. Figures 13A,/, l'lh,i; Feinberg and ited to the outer whorl. On the specimen figured Lorenz, 1973, pi. 2: fig. 10; Scott, 1973a, pi. 2: (Figure 17a,b), it is absent from the last two fig. 3). chambers and very weak on the preceding cham ber. This variability and the radial inflation of chambers also occur in G. puncticulata sphericom- THE INNOVATIVE BRANCH, iozea. However, southern populations of the lat GLOBOROTALIA MENARDII ter contain only four chambers in the outer whorl With the appearance of Globorotalia menardii, while G. saheliana has at least five. Again, the the only major modification of the elongate, B- contrast in northern and southern populations is type chamber was introduced. The new, C-type apparent. Further, specimens resembling G. chamber (Figure 5) is broad and flaring, with a mons, one of the Pliocene descendants of G. raised trailing edge and a leading edge that joins conoidea, have not been illustrated from the the spiral surface at either a right or obtuse angle. North Atlantic (Poore and Berggren, 1974, Tjalsma (1971) and Zachariasse (1975) distin 1975; Poore, 1979). This may also apply to G. guished two forms (4 and 5) of G. menardii ac pliozea. Some isolation is suggested among pop cording to the angle of intersection, but the ulations of G. conoidea in the late Miocene (Figure angular range is slight. Both compare favorably 43). with the Mediterranean lectotype of G. menardii We have interpreted Globorotalia conoidea proposed by Stainforth and others (1978). broadly for, although there is a large amount of The C-type arrangement allows more cham variation in axial form, it seems to be gradational bers to be included in a whorl. The design also and there are strong interregional resemblances moves the greatest spiral dimension of chambers in spiral chamber shape, keel development, and in a radial direction (Figure 5), so tending to aperture. We summarize our view of the various increase overall test diameter. Therefore, the C- 36 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY type chamber might be viewed as a strategy for and superficially, because the taxonomy of this producing a larger shell without significantly ex group is intricate and connections between spe tending ontogeny. The hydromechanical penalty cies in many cases remain obscure. There were of large size was reduced in the menardines by no important changes in shell design after the the good form resistance of the axially com appearance of Globorotalia menardii, but the lin pressed shell (Scott, 1973b). The new form was eage was innovative in many minor ways. A num well suited to the exploitation of tropical waters. ber of species or distinctive variants (Figure 14 The C-type chamber became the trademark of d,e) developed by changes in the number of tropical Globorotalia but was never adopted by chambers in the outer whorl, the shape of the species endemic to regions outside ofthe tropics. peripheral margin, and the rate of size increase Most of the early representatives of Globoro in chambers. There were also changes in the talia menardii are modern in appearance, with shape of the axial profile, but they were much typical C-type chambers and pores that are re more limited than in the G. conoidea lineage. The duced in size. However, some early individuals menardines never developed a highly vaulted are intermediate with G. praemenardii. Blow ventral profile; most species have compressed, (1969:369) noted the intergradation and pro biconvex axial profiles with the greater convexity posed that G. menardii be applied to specimens on the umbilical side. Some individuals are mod in which the sutural limbation extended into the erately domed (Zachariasse, 1975, pi. 4: fig. 1 lb). middle whorl. Limbation is produced by keel That, however, is about the extent of vaulting, formation; hence Blow was attempting to employ and the menardines never exploited this type of the progressively earlier inception of the keel in shell form as did G. conoidea. In the short-lived ontogeny. He considered that, in joint G. prae- Pliocene species, G. miocenica, a dome-like ap menardii-G. menardii populations of Zones Nl 1- pearance is exaggerated by the presence of a flat N13, progressively more specimens achieved spiral side. The common tendency of the men early initiation of the keel in ontogeny. Applica ardine group has been to develop a thin, disk tion of the C-type chamber criterion also points like shell (Figure 7). Examples of this shell form to gradational relationships among G. praemen are found in Miocene populations of G. menardii ardii, G. menardii, and G. conoidea. Bizon and but are more common after the Miocene (Figure Glagon (1978, pi. 8) illustrated specimens with 14^-c). The disk shape is achieved during ontog C-type chambers but with weak keels restricted eny, particularly in the final volution of the test to the later chambers of the outer whorl (G. (Scott, 1973b). praemenardii level of keel development). Con Normally, the menardines have five to six versely, Cita and others (1978, pi. 5: figs. 1-3) chambers in the outer whorl. During the Pli show specimens with strong keels (some with ocene there was experimentation, particularly in limbation, meeting Blow's menardii criterion) but the Atlantic (Parker, 1973; Keigwin, 1982), to with B-type chambers. These are associated with develop multichambered species with more than individuals that they referred to G. conoidea. six chambers in the outer whorl. All of these From the perspective of the later record of the species (e.g., Globorotalia multicamerata, G. mio plexus, it is certain that major divergences oc cenica, G. pertenuis) include individuals with curred in Zones Nl 1-N13, but the level of anal seven or more chambers in the outer whorl; G. ysis thus far fails to indicate well-defined specia- pertenuis includes individuals with as many as 11 tions. That little use has been made of events in or more. Olsson (1973) showed that growth dur the plexus in the middle Miocene biostrati ing ontogeny was complex. The menardines graphic classifications reflects the complexity of were no more successful with the multicham population variation. bered experiment than other planktonic forami We deal with the menardine lineage briefly nifera. All of the Pliocene forms with seven or NUMBER 58 37 FIGURE I4.^a,bf, Globorotalia cultrata (d'Orbigny), Atlantic Ocean 22°07'N, 81°08'W, 270 fathoms. Recent (X 60); c-e, Globorotalia exilis Blow, Folly Point, Jamaica, Pliocene (X 55); g-j, Globorotalia menardii (Parker, Jones, and Brady) {g, X18/fl5, Hangaroa River, New Zealand, upper Miocene (X 110); h-j, cotype locality Paragloborotalia mayeri Zone, Trinidad, middle Miocene (X 70)). more outer chambers were short-lived and be cultrata, and suggested that they might be onto came extinct before the end of the Pleistocene. genetic variants. A larger problem is the similar Connections among these species and their roots ity between the G. menardii-G. cultrata group are obscure, although Berggren and Amdurer and G. tumida. These may represent end mem (1973) postulated a phylogeny (Figure 15). bers of an almost interconnecting morphocline. The historic development of the menardines Brady (1884:692) thought that G. tumida might was intricate and is reflected in the unsatisfactory be only a variety of G. menardii. Schmidt state of their taxonomy. There are several major (1934:52) and Ericson and others (1961:263) unresolved questions. Following Stainforth and considered them conspecific, while Thompson others (1975), Globorotalia menardii refers to the (1982:372) remarked that most Pacific speci middle to upper Miocene populations that devel mens of G. menardii are intermediate with G. oped from G. praemenardii (Figure 1 Ag-j). Many tumida. Bronnimann and Resig (1971:1276) pro post-Miocene tropical populations, which tend to posed G. tumida lata for one such morphotype. be strongly compressed (Figure 146), are placed Variants in which flexuose chambers are formed in the modern G. cultrata, but the relationship of in late ontogeny have been assigned to both this taxon to its close Miocene precursor, and to groups. (G. menardii flexuosa Srinivasan, Kennett other Pliocene menardines, is poorly known. and Be; G. tumida flexuosa (Koch)). Rogl Fleisher (1974:1026) found it impossible to con (1974:752) recorded G. menardii, G. tumida, and sistently distinguish between G. menardii and G. G. cultrata as a single group in a Timor Sea 38 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY 3 MIOCENICA - MULTICAMERATA LINEAGE EXILIS - PERTENUIS LINEAGE - PLEISTOCEN E Z) PLIOCEN E _i Uppe r MIOCEN E Middl e cultrata FIGURE 15.—Phylogeny of some Pliocene-Pleistocene menardine taxa redrawn from Berggren and Amdurer (1973). (Miocene populations of Globorotalia cultrata are probably referable to G. menardii.) sequence, noting that they showed no significant tergradation, Globorotalia tumida has been shown difference in occurrence. In census work, speci by Banner and Blow (1965:1352) to have a sep mens of G. cultrata or G. menardii are occasion arate ancestry from G. menardii-G. cultrata and ally counted with G. tumida (Poore, 1981). to have appeared near the base of the Pliocene. Nevertheless, despite these indications of in Reports indicating their subsequent integrada- NUMBER 58 39 tion require, initially, detailed study of popula a later Miocene paragloborotalid. If this is the tion variation and, as Cosijn (1938:57) urged, an case, then the non-acute profiles ofthe late Mio understanding of life histories in living material. cene forms are the result of a repetition rather Are there discontinuities? This problem, perhaps than a reversal of an evolutionary trend. A pos the most longstanding in globorotalid taxonomy, sible link with a late Miocene paragloborotalid is remains unresolved. Certainly, it is premature to provided by a form such as G. juanai, but the place G. tumida and G. menardii in different stratigraphic record is insufficiently known to subgenera (cf. Kennett and Srinivasan, determine the actual course of scituline devel 1983:120, 151). opment or to determine if there is a discontinuity between G. gigantea and the later scitulines. The Scitulines In light of the general obscurity of the scitu lines, we review some of the important species. Among the remaining Miocene Globorotalia Globorotalia scitula (Figure I6f-h, k-o) is a mod are the scitulines, a seemingly natural morpho ern form that Brady (1882:716) described from logic group of architecturally simple forms. Za a dredge haul near the Faroe Islands. In modern chariasse (1975) included G. scitula, G. subscitula, sediments and in the water column G. scitula is G. gigantea, G. ventriosa, and G. suterae in the seldom numerically abundant, but it is cosmo scitulines, but G. juanai and G. cibaoensis proba politan. The species is characterized by symmet bly should also be added to this group. All show ric, A-type chambers, with four almost equally a close morphologic affinity to G. miozea or G. sized chambers making up the outer whorl; there conoidea but are distinctive in that they have is no tendency towards radial extension of the symmetrically crescentic, A-type chambers, gen shell. Examination of Recent G. scitula specimens erally without keels. They are reminiscent of in the Smithsonian USNM collections, identified early representatives of G. praescitula. In other by various workers, reveals an acute profile respects too, such as axial compression, the sci which, while variable, is never quite as acute as tulines are enigmatically primitive and they give in G. gigantea. Also, no rim has been observed the appearance of being a group of evolutionary on the peripheral margins of the Recent speci "throwbacks." They are taxonomically difficult mens. The wall of the modern form is most often and have been interpreted in various ways (Per glossy and smooth with small, widely spaced, conig and others, 1980). Species limits and pores. However, some populations of G. scitula ranges are poorly known and the lines of descent may have a coarsely porous surface (Saito and are obscure. Despite their broad morphologic others, 1981:138). affinities, it is not by any means certain that the In the Miocene sequence of Venezuela, Blow scitulines represent a phyletic group. Blow (1959:219-221) recognized two scitulines, iden (1969), for example, treated such forms as G. tifying one as Globorotalia scitula and designating scitula, G. gigantea, and G. cibaoensis as links along the other as G. scitula gigantea, a new taxon. At the line of descent of G. miozea. What is clear is the time, he regarded G. scitula as ancestral to that the oldest scituline, G. gigantea (middle Mio G. gigantea because it occurred lower in the sec cene) is architecturally more advanced than some tion. Blow's figured specimen (1959, pi. 19: fig. later representatives (late Miocene), even though 126) of G. scitula is from a level equivalent to the later forms are more diverse. Some later Zone Nil and the holotype of G. gigantea from Miocene scitulines have a somewhat coarsened a level equivalent to Zone N12. Later, Blow wall surface that is suggestive of a relic, honey (1969:355) reversed his view and regarded G. combed texture. The relatively primitive appear gigantea as ancestral to G. scitula. He gave the ance of this texture suggests that they could have lower range of G. gigantea as Zone N6 and G. developed independently of G. gigantea, through scitula as Zone N9. Impressed with the similarity FIGURE 16.—a-e,ij, Globorotalia gigantea Blow {a-c, Pozon, Venezuela, paratype (USNM 625716), middle Miocene (X 85); d,e,i,j, cotype locality Paragloborotalia mayeri Zone, Trinidad, middle Miocene {d,e, X 120; ij, X \ 00));f-h,k-o, Globorotalia scitula (Brady) {f-h. Guide Station 1,32°08'N, 129°06'W, Pacific Ocean, 740 fathoms, Recent (X 110); A-m, DSDP Site 284, 1- 1-100, Southwest Pacific, Quaternary (X 95); n,o, DSDP Site 284, 22-5-20, Southwest Pacific, upper Miocene (X 105)); p-r, Globorotalia juanai Bermudez and Bolli, Well Cubagua-1, 2691- 2703 ft (820.76-824.42 m), Venezuela, paratype (USNM 221849), middle Miocene (X 130); s,t, Globorotalia praemargaritae Catalano and Sprovieri, Section Rossi (Enna), Sicily, upper Miocene (X 135). NUMBER 58 41 between G. gigantea and G. miozea, Blow made sella and Globorotalia, this possibility cannot be G. gigantea the connecting link between G. prae discounted. Another possibility is that G. gigantea scitula and G. miozea. Examination of the original bifurcated from a later G. miozea population material leaves little doubt that the form which through an evolutionary reversal that involved Blow (1959: pi. 19: fig. 126) identified as G. chamber shape only. A third alternative, that G. scitula is the same as his G. gigantea. The holotype gigantea developed directly from a paragloboro of G. gigantea is larger than the hypotypes of his talid ancestor, seems unlikely because of the ad G. scitula, but the unfigured paratypes are over vanced features displayed by G. gigantea and the lapping in size; there are no other distinguishing lack of connecting links. The early record of features. Globorotalia gigantea is also about the Globorotalia gigantea is critical to an interpreta same size as modern G. scitula, a species with tion of its development. Blow (1969:354) gave which it shows a very close morphologic affinity. the lower range of G. gigantea as Zone N6 but It has the same symmetrical, A-type chambers provided no documentation. Indeed, there is still with four almost equally sized chambers in the no good evidence that this species appeared outer whorl and a quadrate test outline. While much before Zone N11, at least in the Caribbean the wall of G. gigantea is never glossy, it is flat region. Blow's (1959) figured specimens of G. and smooth, fully comparable to the walls of gigantea (his pi. 16: fig. 127) and G. scitula (his advanced globorotalids. The only apparent fea pi. 19: fig. 126) both from Venezuela are from a ture distinguishing G. gigantea from modern G. level equivalent to Zone Nil or slightly higher. scitula is its profile, which is often very acute, Bolli (1957) recorded a first occurrence of G. partially rimmed, and occasionally weakly keeled gigantea (as G. scitula) in Trinidad at a level (Figure I6i-j). It is not surprising that Blow equivalent to Zone Nil. This is confirmed by (1969:355) linked this species with G. miozea, our observations. The occurrence of G. gigantea because G. gigantea is as fully developed a glo in the Mediterranean recorded by Tjalsma borotalid as the more advanced forms of G. (1971:63) and Zachariasse (1975:108) cannot be miozea. However, the symmetric chambers and from horizons older than Zone N11. It is possible quadrate test of G. gigantea not only point to a that specimens Blow (1969:354-356) identified specific difference but also suggest divergence as G. gigantea in the earlier horizons, down into from the G. miozea stock. Zone N7, actually belong to G. archeomenardii, Evidence as to whether divergence may have but this would not account for the Zone N6 occurred early or late remains equivocal. The record of G. gigantea. If the early records (Blow, symmetric, A-type chambers suggest a connec 1969:354) are correct, then G. gigantea probably tion with the early representatives of Globorotalia did develop independently from an ancestral praescitula, but the acute, rimmed profile and stock that retained a primitive type of chamber. smooth wall point to a connection to more ad If the early records are wrong, then G. gigantea vanced forms (i.e., G. archeomenardii or G. prae probably developed from G. miozea through an menardii). Therefore, there seem to be several evolutionary reversal in chamber shape. possibilities for the development of G. gigantea. In the Caribbean, Globorotalia gigantea is well A separation of stocks may have occurred at the represented from Zone Nil to Zone N13 or time that the asymmetrical, B-type chamber was N14, but the upper Hmits ofthe species remain introduced in G. praescitula, with a G. gigantea as obscure as its lower limits. While Blow lineage retaining the A-type chamber and follow (1969:354) placed the upper range of G. gigantea ing a course of development independent of the in Zone N15, there appears to be a dearth of later G. praescitula and G. miozea. In this case, reports of any scitulines from this stratigraphic there must have been a very near parallel series interval. Tjalsma (1971:63, fig. 26) very ques in the development of Globorotalia. Considering tionably assigned G. gigantea to Zone N15 in the the close parallel in development between Foh Mediterranean, but the form he figured 42 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY (Tjalsma, 1971, pi. 7: figs. 3-5) is not a typical G. suterae, where the ventral side is distinctly scituline, as it has more than four chambers in raised (Zachariasse, 1975; pi. 11: fig. 5b), this the outer whorl and they increase rapidly in size. development is parallel to that in G. conoidea. Typical scitulines next appear in Zone N16 and However, unlike G. conoidea, G. suterae totally later horizons and seem to be particularly well lacks a keel or rim. In G. nicolae, another upper represented in the Mediterranean. Whether real Miocene Mediterranean form (Figure 17c,d), or an artifact of compendious taxonomic treat there is also marked radial inflation of chambers. ment of a stratigraphically unimportant group, The elevation of ventral surfaces in these taxa is there seems to be a discontinuity in the record reminiscent of the profiles in the earlier G. zeal between the early and later scitulines. andica and the later G. crassaformis, testimony to Some later scitulines appear architecturally the persistent development of this type of shell and structurally primitive relative to the earlier design. Relationships between G. suterae, G. ni Globorotalia gigantea. Of all the scitulines figured colae, and G. praemargaritae were suggested by by Zachariasse (1975) from the Mediterranean Wernii (1977, pi. 5). Several of these scitulines late Miocene, none show any trace of a rim, while occur primarily at Mediterranean and adjacent the profiles tend to be broad and even arched or North Atlantic sites, and their distribution else vaulted. Also, the coarsely perforate surfaces are where may be limited. rather roughened in appearance, in contrast to Possibly belonging to the scitulines is Globoro the smooth, flat surface of G. gigantea. The form talia cibaoensis, but this species has been inter that Zachariasse (1975, pi. 13: figs. 1-3) identi preted in various ways (Blow, 1969; Parker, fied as G. gigantea from the late Miocene Medi 1973; Berggren and Haq, 1976; Perconig and terranean, like Tjalsma's (1971, pi. 7: figs. 3-5) others, 1980). Bermudez (1949:285) described form, has more than four chambers in the outer this species from late Miocene deposits of the whorl. However, the chambers are symmetrical Dominician Republic. It has reasonably symmet and the resemblance to G. gigantea is clearly very ric chambers but, unlike the later scitulines, it close. Yet a rim is totally lacking, and the surface has an occasional, partially formed rim (Cifelli ofthe wall is rather coarse. The G. scitula figured and Belford, 1977:104) and a rather thickened, by Zachariasse (1975, pi. 72: figs. 1-3) has a less blunt profile. acute profile. It compares very favorably with The most primitive upper Miocene scituline is the modern, coarse-walled form of G. scitula, Globorotalia juanai, described by Bermudez and such as that described by Saito and others Bolli (1969:171-172) from Venezuela. The spi (1981:138). Globorotalia subscitula is virtually an ral profile of chambers (Figure 5) is barely elon identical form except that it has a glossy, largely gated and is close to the paragloborotalid shape. nonporous wall. This form first occurs in the Axial compression of Venezuelan specimens is Mediterranean in the Pliocene, and it appears to slight (Figure 16r) and little greater than on a be the same as that which most workers identify primitive specimen of G. praescitula (Figure 6p). as G. scitula in modern sediments and from the Some Southwest Pacific specimens (Scott, 1983, water column. pi. 2: fig. 25) also have ridged, honeycomb-like Two other scitulines that occur in the later surfaces on early formed chambers, as in G. Miocene of the Mediterranean are Globorotalia praescitula. Chamber form, particularly, is more ventriosa and G. suterae (Figure I1e,j). They primitive than in contemporary G. scitula and a closely resemble G. scitula with which they are separate origin is postulated (Figure 2). found associated in Zone N16, but they are dis Globorotalia juanai, or similar upper Miocene tinguished by their tendency towards a broad scitulines (e.g., G. suterae, G. praemargaritae), extension of the umibilical side and inclusion of may have played a significant role in the origin five chambers in the outer whorl. Especially in of several important groups that appear in the NUMBER 58 43 FIGURE 17.—a,b, Globorotalia saheliana Catalano and Sprovieri, Section Falconara, Sicily, upper Miocene (X 85); c,d, Globorotalia nicolae Catalano and Sprovieri, Section Monte S. Nicola, Sicily, upper Miocene (X 105); e,j, Globorotalia suterae Catalano and Sprovieri, Section Sutera, Sicily, upper Miocene (X 110);/,^^, Globorotalia mediterranea Catalano and Sprovieri, Section Rossi, Sicily, upper Miocene (X 110); h,i, Globorotalia saphoae Bizon and Bizon, Strelia, Greece, upper Miocene (x 130). Pliocene. The best documented connection is in which late-formed chambers form a high (ra with the spiroconvex lineage leading to G. hir dial direction) arch and the aperture is low, as in suta. Several taxa that distinguish stages in the the succeeding G. margaritae. However, the um evolution of a keeled, spiroconical shell have bilical surfaces of chambers remain raised, so that been proposed. Globorotalia praemargaritae (Fig spiroconical form is still weak. The specimens ure I6s,t) retains a ridged wall but chambers, identified here as Globorotalia aff. margaritae spirally, are ofthe symmetrical A-type, elongated (Figure 12w,o) correspond with this evolutionary in the direction of coiling. There is only weak to grade. In G. margaritae (Figure I2i,j) there is a moderate compression ofthe peripheral margin. distinct keel. Because the ventral surfaces of The spiral surface of the shell is raised but chambers are now depressed, the axial shape of matches the umbilical elevation of chambers so the shell is more clearly spiroconical. Perconig that shell shape remains biconvex at this stage. and others (1980) considered that these transfor Chamber compression is more advanced in G. mations took place in the later Miocene (Zones martinezi, and the periphery is subacute and tend N16-N17). On the evidence of chamber shape, ing to thicken (Perconig and others, 1980). This we suggest that a form like G. praemargaritae may correspond with rim formation in G. miozea. offers a more direct ancestral connection than G. A very weak keel is developed on G. andalusiana. juanai. Several grades in the sequence may occur 44 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY together as intrapopulation variants. Cita Globorotalia tumida Lineage (1973:1352) proposed G. margaritae primitiva for small forms lacking the keel, which occurs in G. Banner and Blow (1965) regarded Globorotalia margaritae sensu stricto. This taxon corresponds merotumida, G. plesiotumida, and G. tumida as a in evolutionary grade with G. martinezi or G. gradually evolving lineage and used these taxa as andalusiana. Wernii (1977, pi. 6) illustrated the the principal criteria in recognizing the upper intergradation. Miocene Zones N16-N18, particularly in tropi There are no further advances in the subse cal sequences. That they represent character quent history of this lineage. Umbilical surfaces transformations occurring during the late Mio of chambers are less depressed in Globorotalia cene seems fairly clear but whether the transfor praehirsuta, and in some specimens of G. hirsuta, mations developed independently of the G. men axial shape is quite similar to ancestors of G. ardii-G. cultrata group remains uncertain (Bolli margaritae (compare Figure 12g" with Figure and Krasheninnikov, 1977:448). 12o). These later taxa retain the narrow, low Banner and Blow (1965) proposed that the keel of G. margaritae but have a larger umbilicus, lineage developed from Globorotalia lenguaensis signifying greater radial translation of the spiral (Figure 18*2,^), a species that Bolli (1957) de side during ontogeny. Increase in shell size was scribed from the G. mayeri and G. menardii zones reported by Parker (1967:179). (N13-N15) of Trinidad. Globorotalia lenguaensis FIGURE 18.—a,e, Globorotalia lenguaensis Bolli, locality RM 19507 (R. Muhlemann), Pozon Formation, Venezuela, middle Miocene (X 200); bf, Globorotalia merotumida Banner and Blow, Well Cubagua-2, core 2700 ft (823.50 m), Venezuela, paratype (USNM 641928), upper Miocene (X 85); c,g, Globorotalia pleisotumida Banner and Blow, Well Cubagua-2, core 1400 ft (427.00 m), Venezuela, paratype (USNM 641929), upper Miocene (X 75); d,h, Globorotalia tumida (Brady), Atlantic Ocean, 22°07'N, 81 °08'W, 270 fathoms. Recent {d, X 45; h, X 40). NUMBER 58 45 is a small, circular form with a smooth wall, large Banner and Blow (1965) in the Globorotalia mer pores, and a moderately compressed margin. otumida—G. plesiotumida—G. tumida series involves Chambers are elongate in the direction of coiling the spiral shape of chambers formed in later and distinctly of the B-type throughout. This ontogeny. The C-type chamber is already well species is apparently rare and little is known developed in G. merotumida, but this is followed about its variation spectrum. The figure of the by a progressive radial chamber extension in G. holotype (Bolli, 1957, pi. 29: fig. 5) shows a slight plesiotumida (Figure 18c,g) and G. tumida (Figure keel or, more likely, a rim that bounds the entire I8d,h), resulting in rapid increase of shell diam peripheral margin. Blow (1969, pi. 34: figs. 10, eter and a characteristically flared appearance to 11) figured a near topotype that has only a par the outer whorl. In G. tumida, late-formed cham tially formed rim around the periphery. Globor bers are extended to such an extent that they otalia lenguaensis, therefore, is of about the same become virtually of the same design as the T- evolutionary grade as G. miozea in terms of keel type chamber in Fohsella. Indeed, the resem development. The origin of G. lenguaensis is blance between G. tumida and F. fohsi in spiral cryptic. orientation is sometimes quite close (compare Blow (1969:402) introduced Globorotalia Figure I8d with Figure 8a). Note that Pliocene paralenguaensis as a connection between G. len multichambered menardine forms, such as G. guaensis and G. merotumida. An advance shown multicamerata and G. pertenuis, also are often by G. paralenguaensis is the flaring, radially ex characterized by radially extended chambers that tended quasi-C-type chambers formed in later are virtually the same as the T-type. The allo- ontogeny (Blow, 1969, pi. 46: figs. 2,3). In other metric change in chamber shape during ontog respects, however, this species shows little eny is considerable. As late as the middle whorl, change. The periphery is little more compressed chambers in G. tumida may retain a B-type design than in G. lenguaensis (Kennett and Srinivasan, and then change to a normal C-type and finally 1983, pis. 36, 37). The carina shown by Blow to a radially elongate T-type. Trends in size (1969, pi. 46: figs. 4-6) is closer to a rim than a increase, and perhaps also in strength ofthe keel keel. noted by Banner and Blow (1965), are related to The shell of Globorotalia merotumida (Figure the late ontogenetic alteration in chamber shape. I8b,f) is much more compressed axially than The axial shape of the shell shows no progres either G. lenguaensis or G. paralenguaensis. sive trend. Globorotalia merotumida has a thick, Chambers are distinctly acute with all in the rather ventrally elevated profile. But it is suc outer whorl bearing a strong keel. The keel is ceeded by G. plesiotumida, which has an axial initiated at least by mid-ontogeny or, according profile (Berggren and Poore, 1974, fig. 1) as to Banner and Blow (1965), extends throughout compressed as that in G. menardii. In G. tumida ontogeny. This indicates an advanced state of there is a wide, biconvex profile that results, development since, by analogy with other spirally, from the relatively high spiral of the groups, keels first develop in the last several inner whorls and, ventrally, by progressive ele chambers and then extend into the earlier ones. vation of chamber walls towards the umbilicus. Forms with intermediate keel development, such Biostratigraphically, the first appearances of as G. praemenardii, that provide a link between Globorotalia merotumida, G. plesiotumida, and G. G. miozea and G. menardii, or Fohsella praefohsi tumida, as originally proposed by Banner and that links F. peripheroacuta and F. fohsi, have not Blow (1965), remain the primary criteria for the yet been found to connect G. paralenguaensis recognition of the upper Miocene zones in trop with G. merotumida. If G. merotumida did descend ical sequences (Berggren and Poore, 1974; Vin from G. paralenguaensis it represents a unique cent, 1977; Srinivasan and Kennett, 1981a). example of rapid, in toto, acquisition of a keel. While this points to the reality of the character The principal architectural trend observed by transformations, difficulties have been reported 46 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY in distinguishing the taxa (Parker, 1967:180, Its modern counterpart, G. hirsuta, is a more 182; Fleischer, 1974:1027; Vincent, 1977:536). conspicuous element among subtropical assem Jenkins and Orr (1972:1100) considered that G. blages. merotumida might be a juvenile of G. plesiotumida. Inflated Discoidal: Globorotalia zealandica in All three taxa are fully comparable to the Glo troduced this profile in the early Miocene but borotalia menardii-G. cultrata group with which became extinct. A modern version of the design they coexisted in tropical habitats during the is found in G. crassaformis. Miocene. However, a progressive convergence Globose Profile: Reminiscent of the early between the two groups during the later Miocene paragloborotalids, this type of profile is now is not demonstrable. Axial shape fluctuated in found in the quasiglobigerine Globorotalia in development and, in this character, G. plesiotum flata, a highly successful form. ida resembles G. menardii more closely than its These design changes may be related to cli successor, G. tumida. matic changes initiated in the late Miocene, The one distinctive character trend involves which possibly led to better definition of exten the radial extension of the final few chambers sive gyral watermasses. Subtropical gyral waters which became more pronounced between Zones have become the domain of the nonmenardines. N16-N18. If these flaring chambers are ne There has been encroachment into temperate glected, the resemblance with Globorotalia men regions, but the tropical waters have been the ardii is close, particularly when allowance is made preserve of the menardines. The subpolar to for variation. Therefore, while there is good polar waters, with important exceptions, have evidence for a chronoclinal development in the never been successfully colonized by globorotal form of the terminal chambers, this change may ids. We now survey several post-Miocene groups have possibly occurred within populations closely of architectural importance. related to G. menardii. Globorotalia inflata Lineage Later Developments In the perspective of Neogene globorotalid Whereas the dominant feature in the Miocene evolution, in which keel development and cham history of the globorotalid radiation was axial ber compression are major trends pursued by the compression of the shell, substantially greater important lineages, the Southwest Pacific history architectural diversity occurred in the later phase of the Globorotalia inflata lineage is remarkable. of the radiation. The menardine design contin Reversionary trends have resulted in loss of the ued to dominate in the tropical waters but other keel and inflation of chambers. These changes types of profiles, for which there were already were initiated in uppermost Miocene populations precedents in the Miocene, were reintroduced of G. conoidea (close to the Epoch 5: Gilbert and proved successful, especially in the subtrop paleomagnetic boundary). Important features of ical, gyral waters. In the later part of the radia G. conoidea shells at this time were the common tion we find a variety of profiles (Figure 7). occurrence of highly conical individuals (Figure Ventroconical or Truncatuline: In the Mio I3A) and a strong preference for a 4-chambered cene, this type of profile was introduced as var arrangement in the outer whorl. The conical iants among the later populations of Globorotalia forms are commonly identified as G. conomiozea, conoidea. It was exploited afterwards to a much but they are completely transitional to G. co greater extent by G. truncatulinoides. noidea and are regarded as variants of the latter. Spiroconical: Globorotalia panda utilized this The first evidence of modification is the loss of profile successfully during the middle to late the keel on late-formed chambers of a few small Miocene but never achieved a wide distribution. specimens and its reduction in amplitude and NUMBER 58 47 continuity in some others. The relative fre quency of such individuals (Figure 396) increases rapidly (Malmgren and Kennett, 1981; Scott, 1982). In the later stage of the trend, the keel is absent in most specimens and is vestigial in a few (where it appears in incident light as a dense zone around the periphery, perhaps analogous to the rim in a primitive G. miozea). Regressive changes in the keel, leading to its disappearance, are accompanied by decrease in the rate of curvature at the chamber periphery. The abrupt, angular junction between ventral and spiral surfaces in keeled specimens becomes rounded and there is also slight radial inflation of the ventral wall at the periphery. The spiral outline of chambers becomes symmetrically subquadrate rather than asymmetric as in G. conoidea. Populations in which these transformations occur are referred to G. puncticulata sphericomiozea (Figure I9e-h). They are polymorphic in terms of keel develop ment. On a morphotype basis, totally unkeeled specimens could be identified as G. puncticulata sensu stricto (e.g.. Figure 19/). However, conti nuity of variation in keel development and cham ber shape suggest that a single taxon is repre sented. Globorotalia puncticulata puncticulata (Figure I9c-d) has been restricted to subsequent populations in which the keel is completely ab sent (Scott, 1980a). The later history of the lineage in the South west Pacific is less dramatic. Further radial infla tion of chambers occurred in Globorotalia punc ticulata puncticulata and the number packed into the outer whorl declined to about 3.5 (Figure 39a). Shells with strongly inflated chambers (3- 3.5 in the outer whorl) and resembling the mod ern form of G. inflata, appear as outliers in mid- Pliocene populations of G. puncticulata puncticu FIGURE 19.—a,b, Globorotalia inflata (d'Orbigny), DSDP Site 284, 9-1-100, Southwest Pacific, Pliocene (X 85); c,d, Glo lata and become dominant in the upper Pliocene borotalia puncticulata puncticulata (Deshayes), DSDP Site (Figure I9a,b). There were no subsequent major 284, 11-2-20, Southwest Pacific, Pliocene (X 85); e-h, Glo innovations in design, and the morphotype with borotalia puncticulata sphericomiozea Walters {e, 15-6-20, X three chambers in the outer whorl represents the 95;/ 15-6-20, X 100; g,h, 14-6-20, X 85), DSDP Site 284, lower limit in chamber packing achieved any Southwest Pacific, Pliocene, 'ancestor" Globorotalia conoidea where in the radiation. The width of the mor Walters, DSDP Site 284, 16-3-20, Southwest Pacific, upper Miocene (X 45). phologic spectrum developed in the radiation is indicated by a comparison of Figure I9b with 48 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Figure 14^ (G. exilis) or with other taxa (e.g., G. G. bononiensis as variants of G. puncticulata and a multicamerata. Lamb and Beard, 1972; pi. 12: regional component ofthe G. inflata lineage. The fig. 5) in which chamber packing was raised to origin of G. puncticulata does not seem to be about 10. While outer chambers in G. inflata are recorded in Mediterranean sequences but the characteristically inflated, giving a globose axial planktonic record there is interrupted by events profile to the shell, this lessens in some popula of the Messinian salinity crisis. tions, giving the shell a quasiventroconical axial In the Northwest Pacific, Maiya and others profile. Theyer (1973) formally recognized such (1976:400) discussed an evolutionary lineage in forms from the Southwest Pacific Pleistocene as which Globorotalia inflata descended from G. or G. inflata triangula. Comparable variants have ientalis via G. inflata praeinflata. Globorotalia or also been recorded from Pleistocene horizons in ientalis has four inflated chambers in the outer the Gulf of Mexico (Lamb and Beard, 1972, pi. whorl. Spirally, chambers show greater radial 27). The tendency for chamber envelopes to inflation and less extension in the coiling direc reduce their radial globosity increases the resem tion than do those of the Southwest Pacific G. blance of axial profiles with those of the early puncticulata. The aperture is relatively low representatives in the lineage. This resemblance arched. Maiya and others (1976:400) considered can be seen by comparing the figures of G. inflata that chambers in the outer whorl increased in triangula given by Theyer (1973, pi. 1, fig. 6) size more rapidly in G. inflata praeinflata, but and Lamb and Beard (1972, pi. 27: fig. 2) with this is an expression of the change in chamber Figure 19g' of G. puncticulata sphericomiozea. packing that occurs between G. puncticulata and However, while profiles became somewhat an G. inflata. Thus, the Northwest Pacific popula gular, reinitiation of a keel apparently has not tions are distinctive in some characters, although occurred. the gross architectural trends are similar to those Records of the lineage from other regions are in the Southwest Pacific. at variance with that from the Southwest Pacific. Future work on synonymies and variation From a study of South Atlantic material (Rio fields is likely to establish that Globorotalia inflata Grande Rise, 30°S) Berggren (1977:306) con is preceded by widespread, but variable, popula cluded that Globorotalia puncticulata descended tions of G. puncticulata in both hemispheres. from a scituline form that he identified as G. More open, however, is the question of the dis cibaoensis and, in turn, evolved into G. crassafor tribution of the earliest populations of the latter mis. The populations referred to G. puncticulata (G. puncticulata sphericomiozea). Several workers by Berggren (1977, pi. 4: figs. 4-16) have low, (Poore and Berggren, 1974; Ujiie and Hariu, slit-like apertures, which are distinct from those 1975; Oda, 1977; Keller, 1978;) have figured G. in Southwest Pacific populations. Scott (1983) puncticulata sphericomiozea from the North Atlan considered that they represent early stages in the tic and North Pacific, but none have recorded evolution of G. crassaformis and were not con the polymorphic populations that occur in the nected with the G. inflata lineage. Southwest Pacific during keel regression. These Typical populations of Globorotalia puncticu are distinctive as they include specimens in which lata puncticulata occur in Mediterranean Pli the keel is in various relic stages. Their apparent ocene sections but Gradstein (1974:94) held that absence from the Northern Hemisphere may be they did not pass upward into G. inflata. He related to the late Miocene variation in G. co considered that the latter descended from G. noidea. In the Mediterranean and North Atlantic bononiensis, a globose form with a particularly regions, at least, the 4-chambered form found in large, open aperture and less embracing cham the south and from which G. puncticulata spheri bers than G. puncticulata. However, Spaak comiozea seems to diverge never became domi (1981:213, 1983:39) interpreted populations of nant. NUMBER 58 49 In review, the fullest record of the origin of is relevant. In the Southwest Pacific, populations the Globorotalia inflata lineage is found in South closely resembling G. puncticulata were recog ern Hemisphere midlatitudes, the region in nized as a subspecies {puncticuloides) by Horni which modern G. inflata is now most abundant brook (1981a:274) in the upper Pliocene-Pleis and widely distributed. We suggest that it origi tocene, contemporaneous with G. inflata. Their nated in this region as branching populations distribution also suggests that Malmgren and from an advanced, keeled globorotalid. The pri Kennett's (1981:236) model is too simple and mary architectural trend was the development of that G. inflata possibly branched from G. puncti a globose shell. It was achieved by redesign of culata. axial and spiral profiles of chambers and altera tion in chamber packing and probably in coiling Globorotalia crassaformis Plexus parameters. Although there was regression in keel development and loss of chamber compres Since its origin near the base of the Pliocene, sion, the resultant shell is distinct from those of Globorotalia crassaformis has been a relatively mi the lower Miocene precursors of the keeled glo nor component of most temperate to tropical borotalids. Chamber shape, spirally, retained the assemblages and has never achieved the domi elongation of the miozea plexus. Axially, the ven nance of its contemporary, G. inflata, of grossly trally vaulted chambers of the immediate ances similar size and shell form. However, G. crassa tor of G. puncticulata were inflated to produce formis and the plexus of taxa that are either its globose form. The extent of the evolutionary close relatives or descendants are significant in reversal in this lineage can be appreciated when the history of the Neogene radiation both for it is recalled that d'Orbigny (1826:277) originally their re-enactment of some of the principal Mio included Globorotalia inflata in Globigerina, a ge cene trends and for their own peculiar course of neric designation commonly followed until the architectural development. Whereas the lower last two decades. Miocene globorotalid pioneers developed from Malmgrem and Kennett (1981) considered the paragloborotalids by major redesigns, G. cras that the lineage evolved by gradual phyletic saformis possibly arose from a nonspecialized sci transformation. They mapped several long-term tuline globorotalid. Basic transformations were trends (reduction in number of chambers in the obviated and advanced characters (e.g., wall sur outer whorl, rounding of chamber periphery) face) were present at the outset. However, in that are consistent with this interpretation. But contrast to the main course of early Globorotalia gradual phyletic transformation of Globorotalia and Fohsella development, the main trend in the conoidea into G. puncticulata is inconsistent with G. crassaformis plexus was not towards axial the continued presence in Southwest Pacific Pli chamber compression but towards ventral exten ocene strata of keeled populations (G. mons, G. sion or inflation. Some weakly discoidal variants pliozea) that retain the major characters of G. arose in G. crassula, but this design was never conoidea. Their occurrence indicates that G. fully adopted by the plexus. Minor ventral exten puncticulata branched from the keeled stock. sion of chambers was initiated early in globoro Keel regression was relatively rapid in early pop talid evolution by G. zealandica, but that lineage ulations of G. puncticulata and probably identifies occupied a minor position in the Miocene history the period of divergence. Similarly, while G. of the radiation. In the Pliocene, the design was inflata seems to arise by progressive transforma much more successful and culminated in G. trun tion of G. puncticulata populations, there is wide catulinoides, the quintessential ventroconical variation in the latter and divergences may have form. There is close similarity here with the occurred. The status of G. bononiensis and G. conical forms of G. conoidea and its Pliocene praeoscitans, found in the Northern Hemisphere, descendent, G. mons. Equally, there is an inter- 50 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY esting difference. There was a long history of acterized by the smooth wall (often pustuled) of fully keeled shells in the plexus containing G. advanced globorotalids. Chambers have a quad conoidea before ventroconical form developed. rate spiral outline (four chambers in outer whorl) In the lineage leading to G. truncatulinoides, ven and a low slit-like aperture. The axial profile of tral extension, chamber compression, and keel outer chambers is moderately extended ventrally development occurred almost concurrently. and is gently convex below the periphery. Gen We review some major aspects of the plexus: erally, there is no keel. The axial shape of the the origin of G. crassaformis, its relation with the shell is discoidal to weakly planoconvex. G. inflata lineage, variation in keel development, Currently, there is little consensus on the ori features of G. crassula, and the history of the G. gin of Globorotalia crassaformis, and there has truncatulinoides lineage. been some nomenclatural confusion (e.g., Ken nett, 1966). Cifelli (1976b) reviewed the history of usage. Commonly, G. crassaformis appears ab ORIGIN ruptly and gives no indication of its origin (Par The central taxon in the plexus, Globorotalia ker, 1967:176). A well-authenticated evolution crassaformis (Figure 20a,b,i,j) appears early in ary sequence has yet to be documented, but there Pliocene strata in midlatitude sequences, where are several hypotheses (Figure 21). From a study the event provides a useful biostratigraphic da of Italian populations, Colalongo and Sartoni tum in both hemispheres (Vincent, 1977; Keller, (1967) suggested that G. aemiliana was the ances 1978, 1979a). These early populations are char tor. This species is characterized by low crescen- FIGURE 20.—a-b,d-e,i-j, Globorotalia crassaformis (Galloway ronda Blow, DSDP Site 200 1-cc, North Pacific, Pleistocene and Wissler) {a-b, DSDP Site 284, 10-6-40, Southwest Pa (X 10);f~h, Globorotalia aff crassaformis (Galloway and Wiss cific, Pliocene, (X ] 10); d-e, DSDP Site 284, 5-4-20, South ler), Chain Station, 115-6-67, 404 cm. South Atlantic, Pli west Pacific, Pleistocene (X 65); i-j. Chain Station, 115-6- ocene (/;g-, X 95; h, X 100). 67, 306 cm. South Atlantic, Pliocene (X 90)); c, Globorotalia NUMBER 58 51 tic to subquadrate chambers (spirally) and de not detect a consistent trend towards increased pressed to weakly elevated ventral surfaces. ventral elevation, and implied that the depressed Lamb and Beard (1972:52, pi. 2) included G. primitive forms of the previous authors were crassacrotonensis as an intermediate, with greater intrapopulation variants. He considered that G. ventral elevation of chambers. However, Grad crassaformis appeared in Mediterranean se stein (1974:91), from a biometric analysis of a quences in the lower Pliocene, as in other oceans, wider range of Mediterranean populations, did whereas Colalongo and Sartoni (1967, table 1) and Lamb and Beard (1972, pi. 2) proposed that G. CRASSAFORIVIIS BIOSERIES S. ATLANTIC it evolved later in the Pliocene. Zachariasse (Lamb and Beard, 1972) SEQUENCE (1975:112) noted that weakly elevated forms in cluded in Colalongo and Sartoni's bioseries were (RIO GRANDE RISE) common in the upper Pliocene of Crete and were preceded by typical G. crassaformis. Such data seem to invalidate the proposed bioseries. In deed, these forms may belong to G. crassula. Upper Miocene faunas contain small scituline forms with low apertures, crescentic chamber outlines (spiral side), and depressed ventral pro files that have been variously identified as Glo borotalia cibaoensis (by Kennett and Vella, 1975, pi. 5: figs. 4-8; Berggren, 1977, pi. 4: figs. 1-3), G. subscitula (by Blow, 1969, pi. 3: figs. 1-3; Wernii, 1980, pi. 3: figs. 6,7) and G. juanai (by Stainforth and others, 1975, figs. 173, 174; Per conig and others, 1980, pi. 1: figs. 7, 8; Scott, 1983, pi. 2: figs. 21-25). Blow (1969, postscript) first suggested that G. crassformis may have de scended from this group. Kaneps (1975) and Scott (1983) have concurred. Upper Miocene populations of G. juanai from Rio Grande Rise, South Atlantic, have the pustulose surface of G. crassaformis and a low aperture bordered by a prominent lip. They differ in that the axial out line of chambers is less elevated ventrally, the umbilicus is considerably wider, and spiral cham ber shape is crescentic rather than subquadrate (Scott, 1983, pi. 2: figs. 21,22). Subsequent pop ulations include individuals with axial chamber FIGURE 21.—Left, Origin of Globorotalia crassaformis from profiles somewhat more elevated ventrally and G. aemiliana in middle-upper Pliocene (after Lamb and rather similar to those of G. crassaformis, al Beard, 1972). Right, Origin of G. crassaformis from the scituline G. juanai, suggested by a South Atlantic sequence though still retaining a relatively wide umbilicus (Rio Grande Rise, Chain Station 115-6-67, Scott, 1983). (Figure 20/-/i; Berggren, 1977, pi. 4: fig. 3,7,9). Correlation of the South Atlantic sequence with Lamb and Such populations are succeeded by typical G. Beard (1972) zones is approximate. As yet, neither of the crassaformis in the lower Pliocene (Figure 2f)i,j). hypothesized lineages has been closely studied. The example shows that, even with a high resolution stratigraphic record With regard to the question of ancestry, the of population histories, conflicts arise in phyletic interpre hypothesis of Blow (1969) reasonably fits the tation. stratigraphic record of Globorotalia crassaformis. 52 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY If correct, it points to the diversity of architec term decline in number of chambers in the outer ture that arose from the later Miocene scitulines. whorl in G. inflata lineage (Figure 39) reached One branch developed axially compressed, spi the four-chambered stage and coincided with the roconical shells leading to G. hirsuta; but in the mode in G. crassaformis. Subsequently, further G. crassaformis branch ventral elevation of cham reduction occurred in G. inflata, whereas there bers was the primary design feature. was no matching decline in G. crassaformis and resemblance between the taxa lessened. We see RELATION TO GLOBOROTALIA INFLATA LINEAGE the resemblance between Pliocene representa tives as due to convergence. However, even if Broad convergence in gross shell form be stratigraphic evidence of separate ancestries for tween Globorotalia crassaformis and G. inflata lin G. crassaformis and G. puncticulata is dismissed, eage has been widely recognized and variously it is notable that during their wide sympatry in interpreted. Although Cifelli (1965, pi. 4: figs. the Pliocene they retained distinct modes in aper 1-3) figured four-chambered variants of G. in tural shape, perhaps the best morphological dis flata from the western Atlantic that resemble G. criminator. Such data suggest genetic isolation. crassaformis, and noted (1965:18) that end mem bers were difficult to distinguish, it is significant KEEL DEVELOPMENT that Pliocene populations commonly show closest resemblance to each other. Whereas G. inflata As in its presumed scituline forerunner, the usually has 3-3.5 chambers in the outer whorl, junction between spiral and ventral walls of the Pliocene G. puncticulata has four subquadrate chambers in lower Pliocene Globorotalia crassa chambers, which produce a spiral shell profile formis is typically rounded without a keel. Al very similar to that of G. crassaformis (compare though this basic style is continued in many sub Figure I9d with Figure 2O7). Axial outlines are sequent populations, including the large G. ronda also similar (Scott, 1980a). Gradstein (1974) (Figure 20c) and G. oceanica that appeared in the biometrically characterized large Mediterranean upper Pliocene in the tropics, there are forms Pliocene suites and established that variation in with more compressed peripheries. In the Re most chamber and shell dimensions overlapped. cent, some individuals have imperforate rims (Ci Among some samples there were real differences felli and Smith, 1970, pi. 6: fig. 3) and possibly in relative height of the spire and in elongation even weak keels (Cifelli, 1965). Gradstein (1974) of the last-formed chamber relative to shell di found that specimens with imperforate margins, ameter. While aperture shape is predominantly or keels, comprised up to 85% of some Mediter slit-like in G. crassaformis and arched in G. punc ranean Pliocene samples, but these structures ticulata, the variation fields marginally intersect. were absent from others. In the temperate South Barbieri (1971), noting the presence of inter west Pacific, Hornibrook (1982) found that the mediates between typical Globorotalia puncticu populations with rounded peripheries, like the lata and G. crassaformis, suggested that the taxa lower Pliocene forms, disappeared prior to the were end members of an ecologically controlled entry of G. truncatulinoides and were replaced by morphoseries. To the contrary, Berggren (1977) populations with rims or weak keels (Figure considered that there was a phyletic relation, 20d,e). Lidz (1972) observed in Atlantic and with "primitive" G. puncticulata being the ances Caribbean populations that large, angular indi tor of G. crassaformis. However, his "primitive" viduals with rims, or weak keels, predominated G. puncticulata probably refers to specimens in in Quaternary interglacials, while the smaller, termediate between G. juanai 2Lnd G. crassaformis inflated forms were dominant in low tempera (Scott, 1983). We suggest that gross resemblance ture periods. In terms of keel morphogenesis, in shell form arose in the Pliocene when the long the upper Pliocene-Recent history of G. crassa- NUMBER 58 53 FIGURE 22.—a-bf-i, Globorotalia crassula crassula Cushman and Stewart {a,b, DSDP Site 154, 2-6-120, Caribbean, Pliocene (X 55); f,g, S55/f937, Leader River, New Zealand, upper Pliocene-Pleistocene (X 105); h,i, DSDP Site 284, 6-3-20, Southwest Pacific, Pleistocene (X 100)); c,d, Globorotalia crassula viola Blow, type locality Canimar fauna (Palmer locality 1583), Cuba (X 105); e,j, Globorotalia crassaconica Hornibrook, DSDP Site 284, 10-6-40, Southwest Pacific, Pliocene (x 90). formis is comparable with the G. miozea to G. GLOBOROTALIA CRASSULA praemenardii segment of the G. praescitula plexus in that specimens may develop rims or weak This species, like Globorotalia crassaconica, has keels; however, strong folds, uniformly devel strong architectural similarities with G. crassafor oped from midontogeny onwards throughout mis, but is widely distributed in the Pliocene and the population, are absent. Globorotalia crassafor extends to the Recent. A major resemblance is mis, in such a comparison, has not reached the in the subrectangular spiral shape of chambers stage of G. menardii and G. conoidea. in the outer whorl (typically formed by four Weak, somewhat variable, keel development is chambers); but there is a subtle rectification of also found in G. crassaconica, a Pliocene species the leading and trailing edges to produce a shape (Figure 22e,j) found in the southern midlati well compared by Blow (1969:398) with the petal tudes. It is probably a component of the G. ofthe wood violet (Figure 22c). While the spiral crassaformis plexus. Its chambers are strongly outline of the shell is commonly also subquad elevated to produce a ventroconical shell, usually rate, a more lobulate form with less compact with an angular periphery; but the keel, while arrangement of chambers occurs in some large, usually developed, does not form a strong fold, tropical populations (Scott, 1976). The major and only rims occur on some small specimens. component of variation in G. crassula is in the 54 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY axial profile. In tropical populations the ventral moreover it is not an invariant feature, particu surfaces are usually strongly depressed and the larly in tropical populations. Discoidal form is axial shape of the shell is biconvex to compressed uncharacteristic of G. crassaformis but develops discoidal (Figure 22b). Biometric data (Scott, in low-latitude populations of G. crassula. We 1976) indicate that some ontogenetic change oc suggest that G. crassula is a close relative of G. curs, with larger shells tending to be more dis crassaformis, but we cannot resolve whether it is coidal. Although axial form may broadly resem an upper Pliocene branch from the latter or a ble that of G. hirsuta (Parker, 1962, pi. 5: figs. taxon that arose independently, perhaps from 10c,lie), spiral convexity is never strong. Dis another scituline. coidal shells are less common and less advanced GLOBOROTALIA TR UNCA TULINOIDES in temperate regions. Here, the spiral surface of the shell is usually but slightly domed and the Generally, morphoclines are ill-defined in the ventral region elevated. Scott (1976) studied an Globorotalia crassaformis plexus, which contrib upper Pliocene South Pacific sample in which utes largely to the problems in its sytematic treat shell form was ventroconical (Figure 22g) and ment. The exception is the G. truncatulinoides comparable with conomiozea variants of G. co lineage in which there are well-defined trends in noidea. Similar axial profiles were figured by architecture, analogous to those in Miocene taxa. Hornibrook (1981a, fig. 6i) also from New Zea Following Blow (1969), the stem species have land, and by Glagon and others (1973, pi. 1: fig. been taken as G. ronda (Figure 2Sk,l) and G. le) from the Mediterranean. Generally, midlati oceanica, which are differentiated from G. cras tude populations display a spectrum of axial form saformis by their radially inflated chambers. In ventrally, from low-domed to conical. Globoro the G. inflata lineage this feature was retained talia crotonensis, G. crassacrotonensis, and G. ae and associated with reduction in the number of miliana, originally described from the Mediter chambers in the outer whorl (compare Figure ranean, fall within this range and may be variants 19c with Figure 23/); in the G. truncatulinoides of G. crassula. lineage the important early architectural changes Although Kennett and Srinivasan (1983, fig. were an increase in chambers in the outer whorl 16) depicted Globorotalia crassula as the ancestor and a reduction of radial inflation. These rever of G. crassaformis, we consider that the relation sals eventually resulted in a ventroconical shell between these taxa is unresolved. There is gen (compare with G. inflata, Figure 7). Takayanagi eral resemblance in chamber shape (both spiral and Saito (1962:81) described G. tosaensis with and ventral), chamber packing, aperture shape, four chambers commonly in the outer whorl, but and in rather weak keel development (although topotypes include specimens with five, and col the structure is much more prevalent in G. cras lections with up to five have been reported (Stain sula than in G. crassaformis). There is also a forth and others, 1975:413). Five chambers in general ontogenetic tendency for the spiral shape the outer whorl could be simply obtained by of chambers to be weakly crescentic in early halting the ontogenetic decline that occurs in G. whorls and more subrectangular in the outer crassaformis. In the G. ronda group, the alteration whorl. Some populations of G. crassula are diffi is associated with a decline in length of chambers cult to distinguish from sympatric representatives and formation of a well-defined flattish apertural of G. crassaformis (Hornibrook, 1982), and the face. Late-formed chambers show less radial in close similarity in morphology is reflected in flation and tend to extend ventrally, a feature interpretations of G. crassula as the ancestor of also seen in keeled morphotypes of G. crassafor G. crassaformis. Differences are modest. The pet mis and relatives like G. crassaconica. These aloid shape of chambers in G. crassula involves changes result in a shell with a moderately an only a small alteration to the chamber envelope; gular periphery, which may have a thin rim, as is NUMBER 58 55 sometimes present in topotypes of G. tosaensis. and others (1968), and Hornibrook (1976) have The principal advances of Globorotalia truncatu interpreted such forms as variants among inter- linoides (Figure 2Sa-d) over G. tosaensis involve: grading morphotypes (Figure 24). There do not (1) rectification, or straightening of the axial appear to be any consistent differences to uphold profile of chambers, (2) increased angularity of Blow's two-lineage interpretation. junctions between chamber surfaces, (3) devel In New Zealand sequences, Hornibrook opment of a keel, (4) increased ventral extension (1976) found that the keeled morphotype grad of chambers. In addition, the umbilicus widened, ually replaced the unkeeled morphotype (Globor signifying more evolute coiling than in G. tosaen otalia tosaensis) upward, but that the ratio be sis. tween the two was highly variable. Kennett and Globorotalia truncatulinoides is very distinctive Geitzenauer (1969) found in a Southeast Pacific in appearance. It has five to six chambers in the core that the percentage of keeled specimens outer whorl and a profile that is linear or slightly fluctuated widely (8%-98%) and the higher per convex (Figure 2?>b,d). At the periphery, there is centages of keeled specimens were associated a prominent keel which, in larger specimens, with the more tropical type of assemblages. Also, extends to the junction ofthe apertural face with the keeled specimens were noted to have a more the ventral wall. The ventral side may be highly acutely angular periphery, suggesting that keel conical, but this feature varies ontogenetically formation was related to chamber compression. (Cifelli, 1965:21) and geographically (Kennett, Therefore, it appears that while the keel devel 1968). oped by ontogenetic progression, there was not The onset of keel construction, the principal necessarily a uniform phyletic rate of develop feature used in separating Globorotalia truncatu ment. The data of Kennett and Geitzenauer linoides from G. tosaensis, was rapid. From a (1969) suggest that a regional, watermass factor magnetostratigraphically calibrated sequence, may have been involved, with the tropical waters Berggren (1969) reported that keel develop being more conducive to the spread of keeled ment, once initiated on the last formed chamber, forms. extended progressively around the outer whorl Initially, a phase of rim formation only is in in 0.05 m.y. (Figure 39). This accelerating trend, dicated in tropical and subtropical populations (predisplacement of Alberch and others, 1979) (Rogl, 1974:748; Phillips and others, 1968), and has apparently continued since the Pleistocene. also in the North Pacific (Japan, type population A section of a ?sub-Recent individual (Figure 24) of Globorotalia tosaensis). This was succeeded by shows that only the earliest chambers have a period of expanded variation (reflected by rounded chambers as in G. crassaformis. A keel Rogl's sympatric "taxa") as chamber compression is present throughout the middle whorl. increased and keels developed. This phase (about While the architectural trends are well de the base of the Pleistocene) possibly varied re fined, the pattern of change remains obscure. In gionally, depending on watermass characteristics. part, this is owing to the interpretation of Blow A rapid morphocline in keel formation, after (1969:407) that crusted and crust-free morpho which G. tosaensis disappeared, was reported by types of Globorotalia tosaensis and G. truncatuli Berggren and others (1967) from the subtropical noides are members of separate lineages. Follow Atlantic. But elsewhere the duration of this phase ing this view, Rogl (1974) recognized four taxa seems to have been extended as, for example, in branching from the crust-free form of G. tosaensis the Gulf of Aden (Vincent and others, 1974) and in a sequence from the Timor Sea. Rogl differ variation was not clinal (e.g., as in the Southeast entiated these sympatric taxa by small variations Pacific; Kennett and Geitzenauer, 1969). Con in profile, keel development, and encrustation. temporaneous populations at various stages of However, Berggren and others (1967), Phillips keel development may have existed, possibly with AXIAL OUTLINES SHAPE VARIATION OUTER WHORL SHAPE CHANGE IN ONTOGENY outer whorl G. truncatulinoides inner whorl •• outer whorl G. crassaformis NUMBER 58 57 FIGURE 23.—a-d, Globorotalia truncatulinoides (d'Orbigny) weakly conical, bioconvex forms are associated {a-b, Chain Station 61-171, 397-402 cm, North Atlantic, with the cold waters of the high latitudes. More Pleistocene (X 60); c,d. Challenger Station 166B, 39°03'S, 170°43'E, Southwest Pacific, Recent (X 90)); e-j, Globoro recently, Lohmann and Malmgren (1983) stud talia tosaensis Takayanagi and Saito {ef, DSDP Site 200, 2- ied regional differences in axial shape by means cc, North Pacific, Pliocene (X 105); g,h, Chain Station 61- of image digitization and eigen analysis. Loh I7I, 569-574 cm, North Atlantic, Pliocene (X 80); ij, No mann and Malmgren also found that there are bori Formation, Japan, Pliocene (X 130)); k,l, Globorotalia two morphotypes of G. truncatulinoides in the ronda Blow, DSDP Site 200, 1-cc, North Pacific, Pleistocene southern ocean with the weakly conical form (X 75). occupying the higher latitudes. However, in this study the relationship between shape and tem the most advanced (in chamber compression and perature was poorly defined, since there was little keel formation) occurring in the lower latitudes. shape change associated with a strong tempera This phase terminated with the spread of the ture gradient. The weakly conical morphotype advanced population (G. truncatulinoides) was designated as G. truncatulinoides malvinensis throughout the geographic range of the lineage. by Boltovskoy and Watanabe (1981:112). Apart from its potential stratigraphic value, the In the North Atlantic the occurrence of two origin of G. truncatulinoides deserves attention as distinct morphotypes is not immediately evident, it promises unexcelled information on the mor as populations of weakly conical forms have not phogenesis of advanced characters in planktonic been recorded. This absence may be partially foraminifera and insights into their adaptive role explained by the fact that, in the North Atlantic, and dispersal spatially. Globorotalia truncatulinoides is confined to tropi In the Recent, regional variation in axial cal and subtropical waters while in the southern height of Globorotalia truncatulinoides was re oceans it extends into subantarctic waters (Cifelli, ported by Kennett (1968) and Takayanagi and 1971). However, North Atlantic populations do others (1968:148). Kennett's data suggest a clinal show an ontogenetic change in shape. Immature relationship between the vertical extension of the forms are weakly conical while the adults are ventral side of the test and sea surface tempera vertically extended on the ventral side and dis ture in the southern oceans. Highly conical forms tinctly conical (Cifelli, 1965:21). Therefore, the are associated with warm, tropical waters while morphotype found in the high latitudes of the southern oceans might be viewed as a case of arrested ontogenetic development. FIGURE 24.—Axial outlines: Left, Intergradation in axial There are several analogies with the evolution shape within one sample between shells {a,b,) in which late- formed chambers have keels {Globorotalia truncatulinoides of Globorotalia menardii. Both developed marked morphotypes) and those without keels {c,d, G. tosaensis mor compression of chambers. The obvious contrast photypes). Chambers tend to be less compressed at the in the form of chambers is due primarily to axial periphery in the latter (specimens from 711 ft (216:86 m), compression in menardines and radial compres Wairoa Drillhole, New Zealand, after Hornibrook, 1976; sion in G. truncatulinoides. But in both, surface text-fig. 5). Right, Change in axial shape of chambers be area is increased relative to volume. The angular tween inner and outer whorls of G. truncatulinoides and comparison with G. crassaformis {e, section of G. truncatuli apertural face in G. truncatulinoides also serves noides from core MSN-536, Indian Ocean (after Takayanagi to expand surface area and is a design feature and others, 1968, figure 3);/, inner and outer whorls o( e not explored by the ventroconical forms of G. superimposed (the inner whorl has been reflected); ^,A, inner conoidea. In both lineages rim development pre whorl of «,/superimposed on outer whorl of Pliocene speci cedes formation of keels. Further, both origi mens of G. crassaformis (Chain Station 115-6-67, South At lantic, g from 306 cm, h from 404 cm). The inflated, discoi nated in the tropics or subtropics. dal axial profile of juvenile G. truncatulinoides resembles the Apart from the striking architectural contrast late ontogenetic shape of the ancestral G. crassaformis). (which may be of lesser significance hydrody- 58 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY namically), there are contrasts in evolutionary this may be due to the recency of its origin. tempo, in taxonomic diversity and in biogeogra Moreover, the biogeography of G. truncatuli phy. Globorotalia tosaensis represents the rim to noides indicates that it occupies a wider water- incipient keel stage of development; it existed mass spectrum than menardine taxa. The latter for about 1 m.y. In the comparable stage leading have seldom extended beyond the subtropics. to G. menardii, G. archeomenardii and G. praemen Globorotalia truncatulinoides is now a major mid- ardii had a history of over 3 m.y. (Ryan and latitude species that extends both towards the others, 1974, table 7). But G. menardii has led to tropics and poleward beyond the transitional a plexus of multichambered, discoidal variants, zone (Be, 1977:58). Modal axial shapes differ in particularly in the post-Miocene. This has not populations occupying contiguous watermasses been duplicated by G. truncatulinoides. In part. (Figure 40), but speciation has not occurred. Analysis of the Succession Globorotalid Radiations and formation of a keel at the chamber periph ery). In the Neogene radiation, these develop OVERVIEW ments are closely correlated and, in the lower to While we have repeatedly commented on the middle Miocene, remarkably unidirectional. A repetitive patterns of architectural design within keel was achieved only after the wall had become the radiation, Neogene species also show striking fully flattened and the axial profile acutely an resemblances to globorotalid forms ofthe earlier gular. The same trend occurred in Fohsella and Cretaceous and Paleogene radiations (Cifelli, in the Globorotalia praescitula plexus. In the later 1969). The resemblances are all the more re Cenozoic, when the axial profile became inflated markable because the stratigraphic record sug during the development of G. puncticulata from gests that there is no phyletic connection between G. conoidea, the keel was lost. This further sug the three globorotalid groups. Severe reductions gests close structural linkage between these char among the planktonics occurred at the close of acters. the Cretaceous and the Paleogene radiations, and The Cretaceous development was more com the new globorotalid stocks developed from re plex and probably less unidirectional than that sidual planktonic populations composed entirely ofthe Neogene. Bronnimann and Brown (1956, of simple phenotypes. fig. 21) recognized two principal Cretaceous lin This scenario provides the opportunity for eages in which compressed, keeled forms devel "outgroup" comparisons of the Neogene radia oped. Both were derived from coarse walled, tion with groups of independent origin that have quasiglobigerine ancestors which, unlike the mid- developed comparable architecture. Such com Cenozoic paragloborotalids, were not honey parisons are potentially useful in identifying combed, but may have been spinose. Honey adaptive characters and in revealing the influ combed textural patterns seldom developed in ence of founding taxa on subsequent develop the Cretaceous: Hedbergella washitensis (Masters, ments. 1977, pi. 26) is a notable example. The wall All three radiations clearly began with became progressively flattened in one lineage, quasiglobigerine ancestors (Bronnimann and culminating in the smooth-walled Globotruncana. Brown, 1956:513; Walters, 1965:112, Blow, The excellent SEM micrographs in Smith and 1979(1 ):253) and showed important phyletic Pessagno (1973) of Globotruncana from the Mae trends in common (chamber compression, reduc strichtian Corsicana Formation of Texas show a tion in surface relief leading to a flat topography. texture fully comparable to that of Neogene NUMBER 58 59 Globorotalia, except that the Cretaceous forms wall, over which isolated pustules are sparsely have an ornate arrangement of pustules or mur- distributed. It has a compressed axial profile with icae. In the lineage leading to Rugotruncana the a rim, or weakly formed keel. Although much texture assumes a pattern of meridionally aligned less successful than Morozovella, Planorotalites is costellae, a peculiarly Cretaceous feature that is closely isomorphous with Neogene Globorotalia. totally unknown from the Cenozoic. Not only Indeed, Blow (1979) in his typological classifica does it occur in Rugoglobigerina and Rugotrun tion ignored the genus and placed its species in cana, but it is also seen in the Heterohelicidae. Globorotalia. The costellae appear to develop from a coales We compare several major features of shell cence of spine bases (Petters, El Nakhal, and architecture in the three radiations in greater Cifelli, 1983). However, in more highly devel detail. oped forms, costellae became fused into well- AXIAL SHAPE OF SHELL.—Neogene taxa uti formed ridges that rise from a smooth wall (e.g.. lized three principal designs in shell construction Smith and Pessagno, 1973. pi. 25: figs. I-3;8- with direction of chamber compression and rate 10). The end member of the rugoglobigerine of whorl translation along the coiling axis as series, Rugotruncana, is closely isomorphous with major variables. Compression in the direction of Globotruncana as it has a well-developed single or the coiling axis, with low rate of translation, double keel. The latter feature is peculiar to the produced disk-shaped shells, and, with higher Cretaceous. In both Rugotruncana and Globotrun rates of translation, spiroconical shells. Radial cana the keel may develop prior to the develop compression of chambers (approximately normal ment of an acute profile (e.g., R. tiveli and G. to the direction of the coiling axis) coupled with saratogaensis). In later radiations the keel always a low rate of whorl translation produced ventro developed as the periphery became more acute, conical forms. Excellent examples of these three a relation that is consistent with a structural designs occur in the Cretaceous and Paleogene function. The inversion in the Cretaceous devel radiations, with some close replicas (Figure 25). opment pattern suggests that topographic ridges Well-known Cretaceous examples of disk-like on the periphery of inflated, globigerine-like shells include Rotalipora appenninica, Globotrun chambers may have originally had another func cana fornicata, G. mayaroensis, and G. renzi. tion and were preadapted to the structural role Forms with a single keel at the periphery or that emerged as chamber compression devel closely spaced twin keels (e.g., G. stephensoni) oped. resemble Neogene examples more closely than Like the Cretaceous, the Paleogene radiation those like G. linneiana (Figure 25) and G. may developed in several directions from coarse aroensis. In these, the wide spacing of keels cre walled, quasiglobigerine ancestor(s) (McGowran, ates a disk form of uniform thickness right to the 1968). One type includes Morozovella, which has periphery. This form is not encountered in Neo a flat wall punctuated by dense concentrations of gene taxa. spike-like muricae. The shell is highly com Paleogene Planorotalites includes several spe pressed (often into a ventroconical form), with a cies (P. pseudomenardii, P. ehrenbergi, Figure 25) keel at the periphery that consists of fused mur that closely resemble the Neogene menardine icae (Blow, 1979(1):401). Morozovella was by far taxa (Figure 26), although shells are usually less the most successful globorotalid in the Paleo than half the diameter of advanced Neogene gene. Acarinina, and possibly Truncorotaloides, forms. which show various degrees of chamber com As in the Neogene, spiroconical shells are rel pression but lack keels, may represent stages in atively rare in earlier radiations. However, the the development of Morozovella. The other Pa Cretaceous Globotruncana contusa (Figure 25) has leogene globorotalid, Planorotalites, has a smooth a particularly high rate of whorl translation and, 60 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY COMPARISONS BETWEEN RADIATIONS AXMl SECTIONS cneTACBOus PALEOGENE NEOGENE AXIALLY COI\APRESSED-DISCOIDAL SHELLS Globorotalia menardii Planorotalites ehrenbergi Globotruncana linneiana Planorotalites pseudomenardii Globotruncana stephensoni SPIROCONICAL SHELLS Globorotalia margaritae Morozovella lehneri Globotruncana contusa VENTROCONICAL SHELLS Morozovella aequus Globorotalia truncatulinoides ANCESTRAL DESIGNS Turborotalia Globotruncana cretacea pseudobulloides Paragloborotalia opima NUMBER 58 61 in terms of spire height, is a more advanced there is only minor extension of chambers ven spiroconical shell than the Neogene examples trally and the high ventroconical form of the {Globorotalia panda, G. margaritae, G. hirsuta. Neogene Globorotalia truncatulinoides is not de Figure 12). Although some specimens of Moro veloped (Figure 26). Conversely, only the Qua zovella lehneri (Figure 25) have a moderately high ternary G. cavernula approaches the low ventro spire, there seem to be no distinctively spirocon conical form that typifies the Cretaceous radi- ical taxa in the Paleogene radiation. tion. The Paleogene development is closer to the Ventroconical designs, rare in the Neogene, Neogene. In forms like Morozovella velascoensis, are common in earlier radiations. Globotruncana M. aequus (Figures 25, 27b), M. angulata, and M. ventricosa (Figure 25), G. canaliculata (Figure crater there is substantial extension of chambers 27c), and G. elevata are Cretaceous examples. ventrally, and shell architecture resembles that However, in all Cretaceous ventroconical taxa of Globorotalia truncatulinoides. KEEL CONSTRUCTION.—Structurally, the com mon denominator of the Neogene radiation is FIGURE 25.—Axial sections of major shell designs from the development of keels at angular junctions of Cretaceous, Paleogene, and Neogene radiations redrawn from micrographs. Widely separated dual keels as in Globo chambers. Similar structures are a feature of the truncana linneiana (after Pessagno, 1967, pi. 97: fig. 13) Cretaceous and Paleogene assemblages. Al inhibit tapering of chambers towards the periphery and a though critical rates of curvature for keel mor disk-like shell of rather uniform thickness is produced. Sin phogenesis have not been worked out, inspection gle, or very closely spaced dual keeled designs from the suggests that, for a particular type of profile, Cretaceous (e.g., Globotruncana stephensoni, after Pessagno, keels originated in each radiation at comparable 1967, pi. 96: fig. 5) have axial profiles that are more com parable with Paleogene and Neogene taxa. Note that raised states of compression. This may simply indicate ridges are developed on sutures only in Cretaceous designs. that mechanical properties of walls in the three In Planorotalites pseudomenardii and P. ehrenbergi (after radiations were comparable. In Neogene and McGowran, 1968, pi. 4: figs. 7, 12) the degree of chamber Paleogene taxa, keels occur only at angular junc compression compares with the Neogene Globorotalia prae tions and are thus confined to advanced species. menardii. Keels are very weak on all 3 taxa. On Globorotalia However, some Cretaceous species developed menardii there is greater compression and inflational folding (Figure 28) produces a strong keel. Elarly whorls form a keel-like structures before a distinct angular pro much higher spiral in the Cretaceous Globotruncana contusa file was attained (G. saratogaensis, R. tiveli). (after Pessagno, 1967, pi. 96: fig. 16) than in a Paleogene While keel locations are often identical in taxa example {Morozovella lehneri, after McGowran, 1968, pi. 2: from the three radiations, there are differences fig. 5). In comparison, Globorotalia margaritae (after Pos in constructional detail, notably in the method tuma, 1971:331) is a weaker spiroconical design. Ventral extension in Globotruncana ventricosa (after Pessagno, 1967, used to obtain a large cross-section. In Neogene pi. 95: fig. 11) is less than in the last chamber of the taxa, additional lamellae are added to the folded Paleogene Moro2ov^//a aequus {aher McGowran, 1968, pi. 1: wall (Figure 28). They taper rapidly in thickness fig. 4). However, still greater ventral extension is seen in away from the fold (Hemleben and others 1977; Globorotalia truncatulinoides (after Takayanagi and others, pi. 11: fig. 3). The extent to which this technique 1968, fig. 3). Ancestral taxa in each radiation have inflated was utilized in taxa from previous radiations discoidal, or globular, shells with little change in chamber shape throughout ontogeny {Globotruncana cretacea, after seems to have been minor. Planorotalites pseudo Pessagno, 1967, pi. 94: fig. 4; Turborotalia pseudobulloides, menardii (Paleogene, Figure 29c) shows some after McGowan, 1968, pi. 3: fig. 18; Paragloborotalia opima, thickening at the site of the keel (McGowran, after Postuma, 1971:345). Chamber compression in more 1968, pi. 4: fig. 7). However, lamellar inflation advanced shells is always strongest in the outer whorl. There of keels in Neogene taxa is strongest in large, is close similarity in the ontogenetic strategy followed by compressed chambers and the small size of cham taxa from each radiation. Note the wide umbilical area of Cretaceous taxa relative to Neogene forms. {Globorotalia bers in P. pseudomenardii and other Paleogene truncatulinoides excepted). disk-like forms probably explains the weak infla- COMPARISONS BETWEEN RADIATIONS AXIAL COMPRESSION VENTRAL EXTENSION SUPERIMPOSED AXIAL OUTLINES Ghbqrotalia Planorotalites praemenardii pseudomenardii Globotruncana Globorotalia truncatulinoides Moroztvella aequus ventricosa FIGURE 26.—Shell outlines (axial orientation) of taxa with the low ventroconical design of many Cretaceous taxa. Mo similar designs from the 3 radiations, enlarged to common rozovella aequus (after McGowan, 1968, pi. 1: fig. 4) is a diameters and superimposed. In Globorotalia praemenardii Paleogene ventroconical shell with greater ventral extension (after Scott, 1973a, pi. 2: fig. 6) and Planorotalites pseudo ofthe last-formed chamber than in Globotruncana ventricosa, menardii (after McGowran, 1968, pi. 4: fig. 9) the degree of but junctions between chamber surfaces are less angular axial compression of the last-formed chambers is compara than in the Neogene Globorotalia truncatulinoides. Early ble. Neither taxon has fully developed keels. Globotruncana chambers of the outer whorl are also less compressed than ventricosa (after Pessagno, 1967, pi. 95: fig. II) illustrates in the latter. FIGURE 27.—a f Globotruncana fornicata (Plummer), Upper Creek Valley, Texas, Campanian (X 75); d,h Globotruncana Taylor Foniialion, Mustang Creek Valley, Texas, Campan area (Cushman), Upper Taylor Formation, Mustang Creek ian (X 90); b,g Morozovella aequus (Cushman and Renz) sensu Valley, Texas, Campanian (X 105); e,i Planorotalites pseudo lato. Well L.Ci. Hammond No 1, Maryland (Cushman Col menardii (Bolli), type locality P. pseudomenardii Zone, Pointe- lection No. 61873), Paleocene (X 130); c, Globotruncana a-Pierre, Trinidad, Paleocene (X 170). canaliculata (Reuss), Upper Taylor Formation, Mustang NUMBER 58 63 EXAMPLES OF KEEL DESIGNS CRETACEOUS PALEOGENE NEOGENE Globotruncana stuartiformis Morozovella velascoensis Globorotalia menardii weak inflational fold fold reinforced by muricae strong inflational fold very strong inflational fold resembling I-beam FIGURE 28.—Sections through keels of late-formed chambers {Globotruncana stuartiformis, after Banner and Blow, 1959, pi. 2: fig. 4; Morozovella velascoensis, after Blow, 1979, pi. 216: fig. 6, boundaries between wall laminae (dotted) are diagrammatic to show Blow's interpretation (e.g., 1979, pi. 206: figs. 5,6) that muricae develop from the outer lamina; Globorotalia menardii, {left) after ScoU, 1973a, pi. 2: fig. 2; {right) after Hemleben and others, 1977, pi. 11: fig. 4). FIGURE 29.—a,d, Globotruncana area (Cushman), Upper Taylor Formation, Mustang Creek Valley, Texas, Campanian {a, X 690; d, X 300); b,e, Globotruncana canaliculata (Reuss), Upper Taylor Formation, Mustang Creek Valley, Texas, Campanian {b, X 350; e, X 495); c, Planoro talites pseudomenardii (Bolli), type locality P. pseudomenardii Zone, Pointe-a-Pierre, Trinidad, Paleocene (X 455);/, Morozovella aequus (Cushman and Renz) sensu lato. Well L.G. Hammond No. 1, Maryland (Cushman Collection No. 61873), Paleocene (X 580). 64 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY tion. Possibly, there are more advanced examples sions into the umbilicus analogous to those ofthe of lamellar inflation in the Cretaceous (Figure Cretaceous. 28; Banner and Blow, 1959, pi. 2: figs. 2c, 4b). SURFACE TOPOGRAPHY.—The wall of ad However, cross-sections of keels in many Creta vanced taxa in the Neogene radiation is of a ceous and Paleogene taxa were enlarged (some single type, consisting of a flat surface with rela what irregularly) by aggregation of pustules tively few pustules concentrated around the aper (muricae of Blow, 1979) on the external surface tural area. There is no conspicuous coalescence of the fold (Figures 27a,h; 29^). "Beaded" keels or fusion of pustules to form ridge, or node-like in some Cretaceous taxa result from alignment structures, nor do the pustules have any role in of single (sometimes elongate) pustules, which the formation of reinforcement of the keel. In are in close proximity but not necessarily fused. the Cretaceous, a flat wall also developed, but it Coarse, masonry-like aggregations are particu occurs in two different forms. One is very much larly characteristic of the Paleogene morozovel- like the Neogene wall with a smooth surface. lids and, in some taxa, occur at all angular junc However, the pustules do coalesce, especially in tions. No member of the Neogene globorotalid sutural areas and around the periphery (Figure radiation utilized this aggregative technique and, 27a,c,h). In the other (rugoglobigerine) the sur like the double keels of the Cretaceous, it is a face is overlain by costellae that are arranged good example of nontransference of characters meridionally, although the pattern is highly vari from one radiation to the next. able. In primitive taxa the costellae appear to UMBILICUS.—The umbilicus in Neogene taxa form by coalescence of spine bases. In more is usually a poorly defined depression in the advanced taxa the costellae form more regularly ventral surface of the shell in the vicinity of the developed ridges. coiling axis. Generally, there are no calcified The smooth, featureless wall is again achieved structures in the depression. However, Creta by the Paleogene Planorotalites, which is even ceous taxa, especially the more advanced ones, more Neogene-like (figure 27e,i). Pustules are have a large, open umbilicus with elaborate struc relatively minor and, unlike Cretaceous taxa, tures (portici, tegillae) that extend partially into, they do not coalesce to form bead-like structures or completely cover the umbilicus (Figure 27f,h). in sutural areas or around the periphery. In Bronnimann and Brown (1956:508) suggested contrast, Morozovella, by far the most prominent that these structures are best developed on forms globorotalid in the Paleogene, had a wall studded with the widest umbilical depression. Portici and with spike-like muricae (Figure 27). These are tegillae, therefore, may have developed as pro concentrated in the sutural areas and around the tective structures. Minor extensions of the aper periphery, where they make up most ofthe keel. ture were observed by Blow (1979(2); 1047) on Thus, while the planorotalids resemble the Neo Turborotalia pseudobulloides, a founder of the gene globorotalids, the contemporary morozo Paleogene radiation, but conspicuous umbilical vellids show much closer resemblance with the plates did not develop in later taxa. Possibly this preceding globotruncanids. may be significant to functional interpretation SHAPE OF CHAMBERS, SPIRAL SIDE.—We have because the umbilicus in some morozovellids, emphasized the importance of chamber shape, in especially some variants of Morozovella velascoen spiral orientation, for identifying some Neogene sis (Blow, 1979, pi. 99: fig. 1), is as wide as in lineages. However, few novelties were actually some globotruncanids. Umbilici are generally introduced in the Neogene. Crescent shapes (A, small, even closed, on many Neogene species. B types, Figure 5) are as common in the globo Significantly, only in Globorotalia pertenuis, which truncanids, morozovellids, and acarinids as the has a wide umbilicus, are there plate-like exten Neogene lineages. Designs resembling the T- NUMBER 58 65 forms of Fohsella occur in the Cretaceous Rotal points to its apparent adaptive importance. ipora appenninica and R. greenhornensis (Pes Although stratigraphic data and character sagno, 1967, pi. 51: figs. 10, 15). Chamber forms analyses suggest that the Neogene globorotalid in the Paleogene Acarinina praecursoria roeder- radiation was unrelated to its predecessors, it is manni and A. carinata anapetes (Blow, 1979, pi. interesting to review the data from the perspec 86: fig. 3) compare with the primitive T form of tive of improvements in design. Architecturally Fohsella kugleri. Although subquadrate chamber and structurally (but neglecting functionality), outlines do not feature in the Cretaceous, they the Neogene radiation shows the following five are as well represented in the Paleogene (e.g., leads in design. Acarinina bulbrooki, A. pseudotopilensis, Trunco Discoidal shells: largest and most compressed rotaloides, topilensis) as in the Neogene Globoro forms (menardine taxa). talia crassaformis plexus. Ventroconical shells: greatest ventral exten sion and strongest radial compression through out outer whorl (G. truncatulinoides). EVALUATION Keel design: strongest development of infla The outstanding similarities among the radia tional folds (in larger menardine species). tions are in chamber compression, keel location, Surface topography: greatest development of and shell shapes. Axial and radial styles of cham flat surfaces (practically all middle Miocene and ber compression, together with spiroconical, ven later Globorotalia, as well as later Fohsella). troconical, and disk-like shell designs all arose in Apertural area: closed umbilicus, mostly un the Cretaceous and reappeared in later radia modified. tions. The Neogene record shows no major nov All of these traits were anticipated in earlier elties in these designs. However, globose forms, radiations, and comparisons are peculiarly con which appeared late in the Paleogene and Neo strained by lack of data on function. However, gene radiations, did not occur at all in the Cre several can be interpreted as simplifications or as taceous. Convergences in form between the ra advances in design. Earlier radiations produced diations are associated with similar phyletic and smooth, flat walls, but surfaces were often sup ontogenetic strategies. All founding taxa had plemented with costellae, fused pustules, or mur globigerinid, quasispherical chambers (Figure icae. There was no single trend towards a com 25) and, in the course of each radiation, com pletely flat, open surface as in the Neogene. pressed architecture was always introduced late Neogene-Recent Globorotalia still retain pustules, in ontogeny. Such canalization of form and on especially in the G. crassaformis plexus, but they togenetic and phyletic histories suggest that com do not fuse into discernible structures. Yet the mon adaptations were made in the three radia architectural simplicity of the advanced globor tions. otalid wall should be weighed against the success Each radiation has distinctive features. The (e.g., species diversity, duration) of the spiky weak ventroconical architecture of the Creta morozovellids. Selection appeared to favor the ceous is the major example involving shell shape. enhancement of muricae and it might be conjec Many distinctive characters, however, do not in tured that they were functionally important. volve gross form of chambers or shell but occur There is isotopic evidence (Boersma and others, in smaller structures. Surface topography, um 1979) that some morozovellids occupied the epi- bilical apparatus, and keel structure are exam pelagic niche which, in modern oceans, is the ples, and it is at this scale that the influence of preferred location of spinose species (Figure 36). ancestry seems to be most obvious. That conver In contrast, as we mention later, Recent repre gence primarily relates to gross shell form again sentatives ofthe Neogene radiation often occupy 66 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY bathypelagic environments. Biogeography The double keels of the Cretaceous, although elegant in appearance, might be viewed as redun SOME PRECEPTS dant relative to the single support of Neogene taxa. However, the influence of ancestry may be Probably the single most difficult concept to seen here if double keels were due to the conver grasp of the biogeography of planktonic orga sion of pre-existing features to a new structural nisms is that it is dynamic. The difficulty arises role. The single keel of the Paleogene morozo because of a natural tendency to reduce all phe vellids was constructed by concentration and pil nomena to simple, static terms and thus assign ing of muricae along the periphery. It is essen particular physical or geographic boundaries to tially a masonry type of construction that tends species distributions. Yet, the ocean is in constant to be bulky. The simple, inflational keel utilized motion and the movement of the water causes during the Neogene is analogous to the man- faunal displacement; planktonic species, there made laminate type of construction, which is an fore, must be adapted to a mobile existence and efficient structural support. Nevertheless, the they are not easily compartmentalized. We morozovellids constructed ventroconical shells should also realize that the parallels of latitude about as large as G. truncatulinoides and were a are man-made constructs and not, in themselves, successful group. There is no evidence that the natural phenomena. In the North Atlantic (Ci masonry technique of keel construction was in felli and Beni6r, 1976; Cifelli, 1979), it was found adequate. The minor development of lamellar that the distribution of planktonic foraminifera folds in Planorotalites might be taken to indicate makes a sensible pattern if the factors of ocean that they were less advanced than those in Glo climate, dispersal routes dictated by watermass borotalia. But scale is important here. Planorotal circulation, and boundary conditions are taken ids were small taxa and only in large menardine into account. Pteropods show a strikingly similar shells ofthe Neogene are strong folds found. pattern in distribution (Cifelli and McCloy, Apertural and umbilical apparatus, so highly 1983). The pattern of neither planktonic group developed in evolutely coiled Cretaceous taxa, makes much sense if species are grouped accord yet so conspicuously absent in the Neogene, may ing to specific temperature or latitudinal ranges. also be size-related if its function was protective. Of course, the North Atlantic is not typical of all This argument is supported particularly by the oceans, because it is a small basin, has an unusu development of analogous structures in G. perten ally strong boundary current (Gulf Stream), and uis, which, in Cretaceous style, developed a large, a climate markedly skewed with respect to lati evolutely coiled shell. tude. Moreover, the North Atlantic studies deal Relative to earlier globorotalid radiations, only with the advective processes that affect dis Neogene to Recent taxa are characterized by tribution and take no account of the convective simple design and features lost rather than fea processes that also must be of some importance, tures gained. We cannot judge whether design particularly in areas of upwelling. Also, there are was improved. Indeed, with presumed indepen poorly understood biologic factors involved (Ci dence of ancestry, there is no reason to expect felli and McCloy, 1983), so that too literal a improvement. The distinctive characters of Neo reading of the North Atlantic record for inter gene taxa can be characterized as modulating the pretations elswhere, or in the past, is ill-advised. strong (adaptive?) signal of shell shape that unites Nevertheless, there are certain aspects of distri the radiations. The modulating information is butional relationships that should apply to all derived from founders and trends, such as size oceans, present or past. In fact, there is an or that developed within the radiation. dering of foraminifera that seems to be general NUMBER 58 67 throughout the world oceans (Bradshaw, 1959; The above breakdown of faunal divisions, Boltovskoy, 1969; Parker, 1960), indicating a which is paralleled by the pteropods, must be a commonality of certain dynamic processes. In reflection of the climatic constraints on the dis the North Atlantic, as elsewhere, planktonic for tribution of plankton. However, these faunal di aminifera are divisible into cold water and warm visions reflect only the static aspects of distribu water faunas, with the cold water fauna being tion and should not be taken to reflect the total characterized by low diversity and the warm wa pattern of distribution as it actually exists in the ter fauna by high diversity. The boundary be water column or on the ocean bottom. The gyres, tween these faunas is always associated with the rotating in a roughly circular fashion, cause dis boundary that separates the cold temperature placement and expatriation of species beyond waters from the warm gyral waters. In the North their preferred habitats, so that large parts ofthe Atlantic this boundary is sharply marked by the ocean may contain assemblages of mixed com Gulf Stream, a fast set of moving currents, across position and origin. In the North Atlantic, rota which there is a strong temperature gradient. It tion is clockwise, so that displacement is towards is important to recognize that the Gulf Stream is the north on the western side of the ocean and the boundary of a very large body of warm, gyral towards the south on the eastern side. Most of water and not a river of warm water flowing the mixing occurs around the gyral margins, through a cold ocean (Stommel, 1965:174). In which negates the latitudinally compartmental other oceans, which are much larger, tempera ized faunal provinces implicit in the methods of ture gradients between temperate and warm, stratigraphers. There is, of course, a latitudinal gyral waters are less steep and the boundary is component in plankton distribution but, as noted more diffuse. Nevertheless, as a general princi before, latitude is not in itself a fact of nature. ple, one would always expect to find, when pro Stratigraphers are increasingly inclined to rec ceeding from temperate to gyral waters, a low ognize high latitude and tropical zonations (Sri diversity fauna eventually replaced by a high nivasan and Kennett, 1981a, fig. 13). A two-fold diversity fauna of a different species composition. scheme of this sort may carry certain practical The warm water fauna is divisible into sub advantages, but it should also be realized that it tropical and tropical subfaunas, or assemblages, has totally artificial implications. Nowhere could but the distinction between them is not strongly a line be drawn between the areas of applicability marked, since a number of species characterize of the zonations since mixed associations of tem both assemblages. The subtropical assembly can perate-subtropical, subtropical-tropical, and even be thought of as occupying the gyral waters, and temperate-subtropical-tropical forms occur in the tropical assemblage the bounding equatorial various parts of the ocean along gyral margins. current system. While diversity is somewhat Moreover, the latitudinal displacement of species higher, overall, in the tropical assemblage, the may be considerable, as can be seen from a difference is not appreciable. In turn, the cold comparison of assemblages from the western and eastern side of the North Atlantic (Figure 30). water fauna is divisible into temperate, subpolar, On the western side, in the temperate waters and polar assemblages. Diversity is very low in adjacent to the western boundary current (Gulf all assemblages and is lowest in the polar assem Stream) at about latitudes 40°-42°N, the tem blage, which is monospecific. In the North Atlan perate Globigerina bulloides, G. incompta, G. ege- tic, the temperate assemblages occupy the slope lida, and Globorotalia inflata occur in association waters and are separated from the subpolar as with a diverse group of subtropical forms that semblage by the Labrador Current. The polar include species of Globigerinoides and Globigeri- assemblage occupies the high arctic regions and nella aequilateralis, as well as tropical forms such is limited in distribution. 68 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY as Globorotalia cultrata. The tropical forms are nents, carried southward by the eastern arm of rarely abundant, but their presence is conspicu the gyre. This type of latitudinal displacement is ous. The temperate and subtropical forms are not unique to the North Atlantic. In the South brought into association by the mixing that oc Pacific, where the circulation is counterclock curs in the vicinity ofthe boundary current, while wise, G. cultrata is limited to the equatorial re the tropical elements are expatriates that are gion on the eastern side (Parker, 1960) but may introduced by the northward movement of the extend to latitude 35°S or higher on the western gyre. On the eastern side ofthe ocean, essentially side (Fade, 1973). Displacement of tropical forms the same types of mixed assemblage are found, such as the menardines can afford a clue to past but at latitudes between about 10°-20°N. The patterns of circulation. principal difference is that in the eastern assem The Neogene assemblages do not lend them blage, the temperate forms are minor compo selves to a high versus low latitude categorization GENERALIZED DISTRIBUTION OF NORTH ATLANTIC PLANKTONIC FORAMINIFERAL FAUNAS [-jr_r| Tropical/Subtropical mixture i;l|ii Northern/Subtropical mixture ^-jyr Northern/SubtropicalATropical mixture FIGURE 30.—Generalized distribution of major planktonic foraminiferal assemblages in the North Atlantic showing broad zones of mixing (after Cifelli and Benier, 1976). NUMBER 58 69 any more than do the Recent assemblages. This respect to watermasses throughout the world is amply demonstrated by the important discov suggests that the ocean is a kind of huge "mixing ery by Poore and Berggren (1974) of an early bowl," although the actual routes and times of Pliocene mixed assemblage in a DSDP core lo dispersal from one ocean basin to another remain cated in the Labrador Current at about latitude a mystery. Yet, lines of communication are not 50°N. The assemblage contained not only tem always completely maintained. The temperate- perate globigerine and typical subtropical forms subpolar Globorotalia truncatulinoides variant, but also some characteristic tropical elements, characteristic ofthe southern ocean, but absent such as Globorotalia tumida, G. menardii, and in the north, is an example of interregional dif Sphaeroidinella dehiscens. Such an association, in ferences in population structure. Therefore, fact, is typical of the kind found in the Gulf oceanic circulation does not completely negate Stream, as noted by Poore and Berggren. Its the possibility of some genetic isolation, and occurrence some 10° or more north of the pre there is no reason to expect that fossil planktonic sent Gulf Stream therefore has a special signifi species will be totally lacking in interregional cance. It cannot be viewed as an indication of a variation. wayward path of the Gulf Stream during the Pliocene, since the Gulf Stream cannot flow in dependently of adjacent waters. The best as ADAPTIVE STRATEGY sumption is that the mixed Pliocene assemblage The gross pattern of Neogene globorotalid is indicative of a boundary current, like the mod development, showing a strong unidirectional ern Gulf Stream and that the tropical elements trend at its beginning and a more varied devel were introduced via the clockwise motion of the opment after the middle Miocene, suggests that gyre. From this, it would appear that warm gyral the shell modifications occurred as adaptive re water was expanded far north of its present limits sponses to a changing environment. This will be in the western part ofthe North Atlantic during reviewed in the following section; here we deal the early Pliocene (Cifelli, 1976a). with general aspects of adaptive strategy. The ocean is very much a closed system in There is a generally symmetrical relationship which no part, theoretically, becomes completely between the distribution of planktonic foramini isolated. Even a well-defined boundary, such as fera and watermasses at the present time. That the Gulf Stream, does not serve as a complete is, species tend to be cosmopolitan, but at the barrier, as evidenced by the mixed assemblages same time they tend to have preferred habitats. found in its vicinity. Isolated bodies, such as the The symmetry is not, by any means, perfect. detached eddies ofthe Gulf Stream, are ephem There are a few species that show a preference eral entities that lose their identity after a month for a particular ocean, and there are two species or so. The Mediterranean has the appearance of of Globorotalia that are inconsistent in their hab an isolated portion of the North Atlantic, but it itat preferences. Nevertheless, in a given set of is not. Water is renewed from the Atlantic, about hydrographic circumstances, it is usually possible every hundred years and the Mediterranean to predict the overall composition of an assem planktonic fauna shows no sign of endemism blage with a reasonable degree of confidence. (Cifelli, 1974). If planktonic organisms were like Circulation and seasonality are factors that plastic drift cards and immune to the environ strongly affect the composition of planktonic as ment, they probably would inhabit every part of semblages. the ocean, as suggested by the experiments of The modern menardines have made the trop Shannon and others (1973). Indeed, the gener ical waters their special domain (Figure 31) and ally uniform ordering of planktonic species with are associated with water bounded by the North 70 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY and South equatorial currents. They are not relationship with their habitat than the menar confined to these waters, since they are expa dines. At the present time they may extend into triated by currents and may be found in subtrop the tropics but tend to avoid the equatorial do ical and even temperate waters along gyral mar main of the menardines. Their exclusion from gins. Nevertheless, they maintain a good stable this region is a relatively new phenomenon, since relationship with watermasses throughout the they are found fairly commonly in Pleistocene oceans. In all, there are perhaps five menardine sediments. species of which the disk-like G. cultrata is the Of the nonmenardine Globorotalia, G. inflata most common. The menardines appear to be and G. truncatulinoides have proven the most more diverse in the Indian Ocean than else successful. However, both of the species are where. highly inconsistent in their habitat preference. The principal domain of the remaining, non- Globorotalia inflata is a characteristic temperate menardine, Globorotalia is the subtropical water species in the North Atlantic and only rarely is it of the central gyres. Modern Globorotalia that found in abundance in the Central Gyre (Cifelli are endemic, or at least partially endemic, to and McCloy, 1983). In the North Pacific, this subtropical water are Globorotalia inflata (globose species is characteristic of the Central Gyre chambers, no keel); G. truncatulinoides (ventro (Bradshaw, 1959). In the South Atlantic it is conical, keeled); G. crassaformis (inflated discoi mostly temperate, as in the North Atlantic (Be, dal to globose, mostly non-keeled); G. hirsuta 1969). Globorotalia truncatulinoides is a typical (spiroconical, keeled); G. crassula (discoidal, member of winter assemblages in the North At sometimes compressed, usually keeled); G. scitula lantic and North Pacific gyres. However, in the (discoidal, weakly compressed, no keel). In gen Southern Ocean, this species flourishes in the eral, these species have maintained a less stable subantarctic waters and is scarce in the Central ^ 10% RELATIVE ABUNDANCE IN SURFACE SEDIMENTS G. hirsuta FIGURE 31.—Relative abundance (frequencies > 10% are shaded) of taxa representing the major globorotalid architectures (after Be, 1977). NUMBER 58 71 Gyre (Be, 1969). Except for G. hirsuta, the re reported by Boersma and Shackleton in the maining nonmenardine Globorotalia generally do lower Miocene, have been recorded with a pe not occur commonly in the modern ocean. The riodicity of about 0.3 m.y. in a New Zealand reason for the general lack of a stable relationship lower Miocene sequence (Nelson and Burns, with habitat preference is not clear but is remi 1982). Thus the temperature data, like that on niscent of a similar lack of stability on the part of geographic distributions of taxa, should certainly the pteropods in the North Atlantic (Cifelli and be regarded as provisional, and generalized. McCloy, 1983). The upper Oligocene planktonic assemblage was dominated by globigerines and paraglobor otalids. Such taxa used quasispherical chambers AN HISTORIC PERSPECTIVE ON THE throughout ontogeny. About this time, Globo EVOLUTION OF FORM quadrina was the most notable taxon (nonspi nose) in which compressed chambers were A principal feature of the Neogene radiation formed in later ontogeny. The predominant up is the sequential appearance of the various shell per Oligocene architectures correspond with designs found in the Recent. The main early those of modern, high-latitude taxa (e.g., Globi Miocene lineages developed axially compressed gerina bulloides, Neogloboquadrina pachyderma). chambers. Spiroconical populations expanded There was considerably less architectural diver after the early acme of the latter and were suc sity than in the modern planktonic assemblage. ceeded in order by ventroconical and globose Architectures characteristic of modern subtrop forms. About 15 m.y. elapsed between the initi ical and tropical assemblages such as globigerines ation ofthe early lineages and the completion of with supplementary apertures, planispiral taxa, the modern range of shell architectures. What is and compressed globorotalids were absent the significance of this pattern? Does it indicate (Keller, 1983, fig. 2). that new niches became available during the Neo Lower Miocene globorotalids appeared in a gene? period when surface water temperatures were To provide further insight into the evolution rising. Perhaps significantly, there was a parallel of form we examine the distribution of new expansion of Globigerinoides at this time. Tropical architectures and the timing of their arrival in temperatures (Figure 33) rose progressively and relation to the history of marine temperatures. gradually in the lower Miocene, leading to a We select this watermass parameter because its maximum in the interval of Zones N9-N13. history through the Neogene has been quantified However, Boersma and Shackleton (1977) re by oxygen isotope studies and because of its likely ported an earlier temperature peak in Zones N5- influence on life processes and population histo N6 in a South Atlantic sequence (30°S). This ries of plankton. Climatic history provides a event may be related to the appearance of Glo broad guide to the evolution of planktonic envi borotalia praescitula in the temperate Southwest ronments. Although paleotemperature data Pacific about the base of Zone N6. Its entry there from a high latitude site (Figure 32) and from a coincides approximately with a marked increase tropical and high latitude synthesis (Figure 33) in the abundance and distribution of the Globi are considered in relation to events in the glo gerinoides trilobus group, which, like its recent borotalid radiation, there are major fluctuations relatives, was probably a warm water form. Pop in some sequences (e.g., at DSDP Site 357, South ulations ofthe Globorotalia zealandica lineage also Atlantic; Boersma and Shackleton, 1977) that expanded about N6 in the Southwest Pacific. are not obvious in Figures 32 and 33. Further, In the founding period of the radiation (Zones fluctuations of comparable magnitude to those N5-N7) regional differences in architecture 72 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY were minor, suggesting good communication be tween well-dispersed, but relatively small, popu trunca tulinoides lations. However, differences in the biogeogra- phies of the two principal lineages are apparent. Globorotalia praescitula established a wide extra- tropical distribution in this interval, and ex tended poleward to at least 50 °S in the Pacific (Jenkins, 1975; DSDP Site 279) and to 63°N in the Atlantic (Poore, 1979, fig. 3; DSDP Site 408). Fohsella peripheroronda did not extend as far poleward. It was not recorded from the North Atlantic site in this interval, while in the Southern Hemisphere it did not reach northeastern New Zealand (38 °S). Subsequently, however, as ma rine temperatures rose further in Zones N8- N12, F peripheroronda expanded poleward and occurs at both Sites 279 and 408. SURFACE WATER TEMP. °C The mid-Miocene thermal maximum, as de FIGURE 32.—Relation between history of surface water tem picted by Savin and others (1975), coincided with peratures at high latitude Southwest Pacific sites and the the culmination of the early phase of the Neo appearance of some major globorotalid architectures. Tem gene radiation (Figure 33). Axial compression of peratures estimated from oxygen isotope analyses of plank tonic foraminifera from DSDP Sites 277, 279A, 281, lati chambers was the principal architectural trend tudes 48°-52°S (afer Shackleton and Kennett, 1975, fig. 2; in this phase and the only lineage {Globorotalia biostratigraphic data after Jenkins, 1975). zealandica) not to pursue this trend was the least G. tumida G. menardii G. arctteomenardii G zealandica G. peripiieroronda 30 °c FIGURE 33.—Synthesis of tropical and high latitude temperature regimes (Oligocene-Quater- nary), after Savin, and others, (1975, figs. 6-7a). Events in the tropical records (at right) of Globorotalia and Fohsella are positioned after Blow (1969). Events at left are located by their record in the temperate Southwest Pacific. Some detailed high latitude data are given in Figure 32. NUMBER 58 73 successful (in population sizes and distribution). peratures were rising, G. praemenardii ranged However, Fohsella and the Globorotalia praesci very widely. Subsequently, populations were par tula plexus recorded significantly different his titioned into G. conoidea and G. menardii. Globor tories during the build up to the temperature otalia conoidea, architecturally a fully keeled ver maximum. In Fohsella, the branch leading to F. sion of G. praemenardii, maintained the latter's robusta originated about Zones N9-N10 but broad latitudinal distribution. In contrast, the there was no comparable divergence in the G. disk-like G. menardii became centered in the praescitula plexus during this period. Further, tropics (Figure 35). Again, however, there is an the distribution of the innovative populations of exceptional distribution in the North Atlantic the Fohsella robusta branch began to progres where it extended to at least 57 °N (Poore and sively contract and to become confined to warm Berggren, 1975), as well as into the Mediterra waters in the Pacific (Figure 34). In this ocean nean. On this basis, Cifelli (1976a) and Cifelli the distribution of F. robusta, the most advanced and Glafon (1979) proposed that there was a member, lies close to the modern tropics, highly expanded mass of warm gyral water in the whereas contemporary populations of G. prae Atlantic during the upper Miocene, with the menardii maintained the wide distribution that western boundary of the gyre in the vicinity of the G. praescitula plexus had previously estab Newfoundland. This expansion persisted into the lished. Data from the western North Atlantic do lower Pliocene in the western Atlantic. Retrac not conform to this simple pattern, as there are tion occurred in the east, however, as suggested records (Bartlett, 1968) from 46 °N that proba by the absence of the menardine group in the bly reflect the operation of a Miocene Gulf Mediterranean and adjacent Atlantic. There is Stream that introduced tropical planktonic as no suggestion of similar poleward expansion in semblages to a region that now supports subarctic the Southwest Pacific. In the latitudes of New taxa (Cifelli and McCloy, 1983). Zealand (34°-47°S) G. menardii appeared about The middle Miocene temperature maximum Zone N15, significantly after its origin in the was followed by a minor decrease in the tropics tropics. Specimens are small and are rarely found but a major decline in the temperature of high beyond 40 °S. southern latitude water (Figure 32). As we have The major feature of the later phase of the noted, it is quite uncertain whether the change radiation is that novel architectures developed in temperature regime was a factor in the extinc beyond the tropics during the upper Miocene. tion of Fohsella robusta. However, it is likely to Although there are earlier prototypes associated have led to greater differentiation of water- with Globorotalia praemenardii, distinct spirocon masses between the poles and the tropics. Savin ical populations of G. panda did not develop until and others (1975) attributed the thermal decou about Zone N14 in the New Zealand region of pling to the development of the modern circum- the Southwest Pacific, and the strongest spiral Antarctic circulation and thermal isolation of convexity occurred still later (about Zone N16). Antarctica, which resulted in a redistribution of The largest populations occur north of 40°S. solar energy. Berger and others (1981) further Globorotalia panda occurs northward to about analyzed the change. Loutit and others (1983) 30 °S in the Southern Hemisphere (DSDP Site showed that in the South Pacific oceanic thermal 206, South Pacific; Rio Grande Rise, South At structure substantially changed (vertically and lantic), and Poore (1979, table 5) recorded it horizontally) and considered that the warm from DSDP Site 410 in the North Atlantic South Pacific subtropical gyres became decou (45 °N). The absence of records from the tropics pled from the Southern Ocean as zonal circula possibly indicates that, like its modern counter tion developed. Such a new regime may have part (G. hirsuta), it inhabited the subtropical to had an important effect on the biogeography of transitional zones. The distribution of G. panda the Globorotalia praescitula plexus. When tem possibly correlates well with the upper Miocene 74 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY PACIFIC DISTRIBUTION OF POHSeUA F. peripiteroronda i 1-60 F. peripiteroronda* .—F. periptieroacuta • -.- F. rotxjstaO G. praescitula plexus only % F. periptieroacuta • FIGURE 34.—Paleobiogeography oi Fohsella in the Pacific (modified from Saito, 1977). Devel opment of a large, axially compressed shell (culminating in F. robusta) occurred as populations contracted towards the Central Pacific. However, the smaller, more primitive F. peripheroronda continued to occupy southern temperate water. Saito's records of F. lobata have been amalga mated with those of F. robusta. Axial outlines of topotypes of F. peripheroronda and F. peripheroacuta, and of the holotype of F. lobata (here regarded as a synonym oi F. robusta) are from Blow and Banner (1966, pi. 2: figs. 3-4, text-fig. 4-1^) and are redrawn to a common scale. OCEANIC DISTRIBUTIONS OF MENARDINE AND CONOIDEA GROUPS IN UPPER MIOCENE iiirimoiiuiijii G. menardii joint occurrences and allies FIGURE 35.—Major partitioning in the biogeography of the Globorotalia praescitula plexus developed in the upper Miocene. Axially compressed, menardine taxa beame centered on the tropics whereas the more ventrally vaulted G. conoidea group (architecturally similar to the ancestral G. praemenardii) occupied temperate watermasses. However, there are broad zones of mixed assemblages at the interface of the menardine and conoidea provinces. In the North Atlantic the northward extension of tropical taxa in the upper Miocene was greater than in modern seas (Figure 30). (Data from DSDP sites after Berggren, 1984, fig. 2); menardine records include G. menardii, G. limbata, G. plesiotumida, and G. merotumida.) NUMBER 58 75 emergence ofthe subtropical gyres in the Pacific. Pliocene in subtropics and tropics. The develop The earliest ventroconical shells appeared still ment of the strongly ventroconical G. truncatu later in the upper Miocene thermal decline. As linoides lineage is best recorded in subtropical with the spiroconical Globorotalia panda, the ev and tropical sequences, although a variant form idence is primarily from the Southern Hemi now shows a preference for subpolar waters in sphere midlatitudes. Throughout their history, the Southern Ocean. southern populations of G. conoidea included in Are there correlations between Neogene and dividuals in which chambers extended ventrally. Recent distributions of taxa with similar shell This feature developed strongly in the upper designs and does the order of appearance of most Miocene (about Zone NI7) and particularly designs correlate with watermass history? The in crust-free individuals. In some, the extension paleogeography of taxa with axially compressed, is as pronounced as in G. truncatulinoides. North menardine shells most closely corresponds with ern Hemisphere relatives of G. conoidea do not the Recent distribution. This design evolved dur show marked ventroconical form (Figure 13^,r). ing a period of rising marine temperatures and A further indication that southern populations has since been associated with tropical and sub were relatively isolated from northern ones in tropical watermasses. The distribution of fossil the upper Miocene is the reduction in the num spiroconical taxa may correspond quite closely ber of chambers in the outer whorl to about four with that of their modern counterpart, Globoro in the former, while the latter retain five cham talia hirsuta. Their paleobiogeography may be bers. The ventroconical development in south related to the differentiation of subtropical to ern populations of G. conoidea continued into the transitional watermasses after the middle Mio basal Pliocene (as G. mons) and then ceased. It cene. was much less successful (in terms of geographic Ventroconical and globose designs show less distribution) than was achieved subsequently by consistent biogeographic patterns. Globorotalia G. truncatulinoides. mons and G. conomiozea morphotypes of G. conoi The most dramatic architectural development dea preferred southern temperate water, in the second phase of the radiation probably whereas G. truncatulinoides probably arose in originated in the southern midlatitudes near the warmer water and subsequently spread into base of the Pliocene. Onset of chamber inflation cooler environments. The globose G. inflata (and shell globosity) in Globorotalia puncticulata maintains largest populations in southern tem reversed the primary architectural trend of the perate water (its ancestors may have originated first phase ofthe radiation. Eventually G. inflata there), whereas a similar globose design in the G. became one of the principal extratropical fora crassaformis plexus (G. ronda) occupied subtrop minifers, demonstrating the high degree of plas ical to tropical environments. Such examples sug ticity in shell design and adaptive potential ofthe gest that there is not a close correlation between G. praescitula plexus. watermass type and certain shell designs. Indeed, By mid-Pliocene all major shell designs found the history of G. truncatulinoides shows that a in the Recent had been implemented at least taxon may develop an advanced design in low once. Repetitions of forms characterize the late latitudes and then expand poleward. These con history of the radiation. Speciation occurred in siderations possibly call into question the extent the tropical menardines, but the basic, axially to which the warm water preference of the men compressed architecture was always retained. ardine design is due to architecture per se. Nev Another spiroconical form, Globorotalia margar ertheless, the history of design developments in itae, developed near the base of the Pliocene, dicates clearly that diversification occurred in a probably from a scituline. Globose forms of G. relatively short period in the upper Miocene and crassaformis (G. ronda) appeared in the upper Pliocene. It seems unlikely that this is simply 76 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY coincidental. It occurred at a time when temper Planktonic radiations into bathypelagic habitats atures of high southern latitude water were very terminated when these conditions led to anoxic low, but with short-term oscillations (Blank and events that caused ecosystem "crashes." In addi Margolis, 1975; Kennett and others, 1979), while tion, Caron and Homewood (1983) considered those of tropical water were high (Figure 33). that bathypelagic taxa, characterized by ad Keller (1979b) produced evidence of oscillatory vanced architectures like those of the globoro temperature regimes in the midlatitudes of the talids, tended to be K-strategists, with longer life- North Pacific at this time, as did Zachariasse and cycles, larger individuals, and smaller popula Spaak (1983) from the Mediterranean. Such re tions than the epipelagic r-strategist globigerine gimes imply greater differentiation of water- taxa, which retained conservative shell designs. masses, an expanded range of potential habitats, MacArthur and Wilson (1967:147-180) discuss and possibly improved isolation of populations K- and r-selection. undergoing architectural transformations (allow To what extent does the evolution of architec ing founders a greater chance of survival). This ture in the Neogene globorotalid radiation fit scenario contrasts with that of the lower and this model? An important perspective is provided middle Miocene, when the thermal gradient be by the bathymetric distribution of modern glo tween poles and equator was considerably re borotalids. duced. The very broad distribution of such taxa Because the vertical distribution of many taxa as Fohsella peripheroronda, Globorotalia miozea, is wide and highly variable. Be (1977:28) cau and G. praemenardii and the limited amount of tioned that their depth classification is valid only architectural diversity may indirectly reflect in a statistical sense. The depth at which maxi much weaker differentiation of watermasses. mum concentration of specimens occurs can shift very rapidly. Sampling by Fairbanks and others (1982) in the Panama Basin showed that G. theyeri BATHYMETRY AND ARCHITECTURE (a compressed variant of G. crassula) moved As planktonic foraminifera occupy the upper about 170 m per day over a vertical distance of few hundred meters ofthe modern oceans, their 600 m. Various factors, including stage in ontog biogeographic domain has a significant third di eny, reproduction, watermass location, and po mension. Hart (1980) and Caron and Homewood sition of trophic resources (Hemleben and Spin- (1983) have stressed the biogeographic impor dler, 1983) influence the daily and seasonal dis tance of the vertical distribution of planktonic tribution of populations. taxa and have proposed that the repeated adap Although the constraints just noted prejudice tive radiations that characterize their history rep generalizations, data from plankton tows (sum resent successive attempts to colonize bathype marized by Berger, 1969) support isotopic data lagic environments. Analogous with Be's (1977) (Lidz and others, 1968; Oba, 1969; Hecht and classification of modern depth habitats, "bathy Savin, 1972) that globorotalids are the predom pelagic" loosely signifies the zone from 100 m inant taxa in the deepest habitats occupied by down to about 1000 m. Primarily from Creta planktonic foraminifera (Figure 36). These are ceous evidence, these authors have argued that generally below the photic zone and the tropical colonization of deep water and development of thermocline. advanced architectures (including globorotalid Axially compressed menardine shells tend to styles) occurred when upper levels of oceans were maintain higher positions in the water column well stratified, currents sluggish, and upwelling than the ventroconical G. truncatulinoides. As was reduced. These conditions are correlated discoidal architecture evolved well before ven with periods of warm, stable climate in which sea troconical, it might be argued from premises of level was rising and nutrient supply diminishing. a bathymetric radiation, that ventroconical shells NUMBER 58 77 represent a further penetration of deep plank ORDER OF SETTUNG PREFERRED tonic environments. However, this conclusion is DEPTH HABJTATS at variance with the evidence of G. scitula, for METERS example. The architecture of this taxon resem 0 bles that of G. praescitula, which was one of the G. tumida spinose taxa, P. obliquiloculata Globigerinoides Globigerina founders of the radiation and, in terms of the S. detiiscens spheroidal chambers with slight overlaj} bathymetric theory, probably epipelagic. In nei G. congtomerata ther is chamber compression advanced. Yet mod Globigerina as above, also compact spherical or globose shells (Orbulina 50 ern populations of G. scitula occupy particularly Pulleniatina Candeina) deep sites (500-1000 m) in the Antarctic (Be, 1977:26). G. inflata Settling rates of shells are possibly relevant to some spinose taxa with extended (digitate) chambers (H. digitate colonization of bathypelagic environments. As G. adamsi) but mainly Glotmrotalia well as size, and the relative densities of (shell + with compressed, G. crassaformis smooth-walled chambers organism) and ocean, the rate of passive sinking N. pachyderma is affected by shell shape (Hutchinson, G. falconensis /v. dutertrei 1967:260-270; Smayda, 1970:357). On a water G. conglobatus depth model of globorotalid evolution, advanced Order of increasing depth architectures might provide hydromechanical advantages relevant to maintaining particular po G. cultrata G. cultrata sitions in the water column. Empirical data (Fig ure 36) on shell settling rates is flawed for eval uating this question because it is based on empty shells and entirely neglects effects of spine loss G. truncatulinoides (on globigerines) and of life processes (e.g., vac uole formation and lipid concentration; Ander son and Be, 1976:17) that considerably influence buoyancy. However, the data show that spinose Globigerina Globigerinoides globigerine taxa have the slowest rates of de Candeina G. crassaformis scent; this is consistent with their preference for Hastigerina the photic zone. Globorotalids have a wide spec FIGURE 36.—Right, Summary of data on depth stratification trum of rates and there is no simple relation of Recent planktonic taxa (Be, 1977). The globorotalid between their shape and settling velocity. Size order is an average ofthe ranked data compiled from several probably accounts for the rapid sinking rate of studies by Douglas and Savin (1978). Note that Globorotalia scitula (not shown) occupies deep sites (500-1000 m) in the G. tumida (Figure 36). Menardine shells are the sub-Antarctic (Be, 1977:26). Left, Order of settling velocities largest in the Neogene planktonic assemblage, (after Berger and Piper, 1972). and a phyletic trend for size increase occurred early in their history as axial compression of than with occupancy of a deep position in the chambers developed. Discoidal shape offers im water column. However, the globose shape of G. proved form resistance (Hutchinson, 1967:265; inflata should, theoretically, have poorer form Scott, 1973b: 145) and it may have developed in resistance than discoidal shells (its experimental the G. praescitula plexus and Fohsella as a tech velocity is high. Figure 36), and such a design nique for reducing the sinking rate of large might facilitate depth migration. shells. With all other factors held constant, dis While there is no firm evidence that the foun coidal shape will reduce settling velocity and its ders of the Neogene globorotalid radiation were evolution relates more simply with size increase epipelagic, the onset of encrustation in southern 78 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY populations of the G. praescitula plexus within Evolutionary Patterns Zone N7 may indicate occupancy of deep water We have traced the history of Neogene glo quite early in the phylogeny of that group. Doug borotalids over a period of about 20 m.y. While las and Savin (1978:179) gave isotopic evidence the review has pointed to various biostratigraphic that Fohsella was deep dwelling by Zone N12. and taxonomic problems, there are nevertheless Further, the early history of the radiation some aspects relevant to current issues in evolu matches some features of the Cretaceous scena tionary biology. The review is made at three rio depicted by Caron and Homewood (1983). levels: Firstly, we briefly summarize the shape of Seas were transgressive (Berger and others, the phyletic tree, the macroscopic record of glo 1981), ocean temperatures were rising, and var borotalid evolution. Turning to the lowest level iation patterns and the biogeography of the ma of analysis, we note some features of ontogeny jor lineages suggests that watermass differentia that influenced the history of lineages. However, tion was weak. Bathypelagic populations devel most of the discussion concerns the intermediate oped, at least in the southern oceans. But envi level and deals with relationships of populations ronmental changes during the upper Miocene and taxa that form the elements of the phyletic and Pliocene (regressive seas, oscillating but gen tree. erally cooler ocean climate at high latitudes, in tensified ocean circulation and perhaps weaker SHAPE OF THE PHYLETIC TREE stratification) match those which Caron and The tree shown in Figure 2 combines hy Homewood regard as unfavorable to deep water potheses about relationships with more factual colonizers. Their model predicts habitat contrac data on taxonomic ranges. There are several tion in such conditions, with conservative, globi principal features. gerine architectures predominating. In fact, the The radiation has multiple roots and repre record in this period was of architectural diver sents a set of lineages or plexi that followed sification in the globorotalids, particularly be common morphological pathways. Berggren yond the tropics. There is no indication of habitat (1966) and McGowran (1968) postulated a single contraction. founder taxon {Turborotalia pseudobulloides) for There is insufficient information on life proc the Paleogene radiation. Neogene globorotalids, esses and trophic patterns of modern globorotal in contrast, did not develop after a plankton crisis ids (Be and others, 1977) to allow confident like that at the Cretaceous-Tertiary boundary assessment of their relation with shell design. and a wider range of potential founders existed Whether globorotalids are K-strategists with long in the Oligocene than in the lower Paleocene. In life cycles, and whether this also has a bearing on this respect the Neogene radiation may be more architectural specialization are unknown. comparable with the Cretaceous. We conclude that, while there is evidence that The number of separate roots in the tree is the habitat of Neogene-Recent globorotalids ex uncertain. We show five, but this rises if the tended over a considerably greater bathymetric Globorotalia scitula plexus had a separate origin. range than that of the spinose globigerines, no Conversely, there may have been as few as three close relation between architecture and pre roots if the G. tumida lineage belongs to the ferred depth habitat is apparent. Architectural menardine group (probable), and the G. crassa innovation seems to be more closely correlated formis plexus arose from the scitulines (possible). with climatic and ocean histories than with inva Kennett and Srinivasan (1983) postulated three sion of deep oceanic environments, although this roots for the groups we have studied, but their occurred. Recall that some Paleogene morozo tree structure is substantially different. vellids, counterparts of the Neogene ventrocon Diversifications occurred particularly between ical design, seem to have occupied epipelagic Zones N9-N13 and between Zones N17-N19. rather than bathypelagic environments. The earlier, in a period of ameliorating climate. NUMBER 58 79 saw the rise of axially compressed taxa. The later in late ontogeny (decline in Globorotalia inflata occurred after marked deterioration in high lat lineage, increase in some menardine taxa). As itude climate and involved an expansion of ar with chamber compression, this is a strategy of chitectural designs. late ontogeny. Because of its longevity, and diversity of spe While the effect of earlier onset of chamber cies and architectures, the Globorotalia praescitula compression in successive populations established plexus stands out as the central element of the a recapitulatory pattern in phylogeny, this does tree. The radiation would have been substantially not clarify the significance of the strategy in limited after the middle Miocene had this plexus contemporary populations. Functionally, the on gone the way of Fohsella. set and strongest development of chamber com PATTERN IN INDIVIDUALS pression at the latest stages of ontogeny suggests Evolutionary advance has to be implemented FOHSELLA tINEAGE via individuals and the ontogenetic pattern SHAPE CHANGE DURING ONTOGENY greatly influences the macroscopic evolutionary inner pattern. There are several important common whorl factors in the ontogeny of many taxa in the radiation. The outstanding feature is that increments in chamber compression invariably occur initially in the last few chambers of the outer whorl (Figure 37). Relatively gradually, compression of chambers is implemented progressively earlier in ontogeny. Within an individual it is generally weaker in the middle than in the outer whorl, and chambers of the inner whorl (close to the proloculus) are usually unaffected (Figures 24, 37). Similar pat terns occur in shells from earlier radiations (Fig peripheroacuta ure 25). Increase in size of adults occurs generally within lineages. Because the number of chambers formed during ontogeny does not vary greatly c (about I5±3) in the history of several lineages, increment in growth rate is likely to have been a peripheroronda general strategy for size increase (Figure 38). However, in axially compressed designs, rate of expansion of the radial diameter of shells is also assisted by changes in chamber shape. C-type chambers in menardine taxa, and advanced T- Q type chambers in G. tumida and in the later fohsellids are examples of this technique. As with Icugleri changes in axial profiles, these are most promi FIGURE 37.—Axial shape of chambers in Fohsella (sections nent in late ontogeny (outer whorl). redrawn from Postuma, 1971:323, 325, 347, 349). In the early taxon {F. kugleri), little change in shape occurs during Coiling parameters (rates of vertical and hori ontogeny. In succeeding taxa, compression increases pro zontal translation of whorls) are fairly uniform gressively in late-formed chambers (outer whorl). Chambers in ontogeny. However, the number of chambers in the middle whorl show weaker and less clearly progressive per whorl (packing) is varied in several lineages change. 80 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY that it was an architectural response related to the hydrodynamic penalties of size. shell size. Although still poorly documented (and If globorotalid innovations had resulted from unfortunately minimized in our SEM illustra abrupt developmental changes in early or mid- tions), size increase was a feature of axially com ontogeny, taxonomic distinctions and phyletic pressed Fohsella and Globorotalia in the early patterns in the radiation would have been more Miocene. Chamber compression was superim discernible. Instead, during episodes of morpho posed on this trend. Compression of chambers logical transformation, innovation late in ontog increases surface area, and probably form resist eny produced a "noisy" signal. There is often a ance. Disk-like shells, theoretically, will sink more spectrum of adult specimens in a sample, in var slowly than spherical (Lipps, 1979:73; Scott, ious stages of advance, depending partly on the 1973b). While the organism has other systems proximity of a particular ontogeny to completion that affect buoyancy, it is plausible that the "cost" and partly on the amount of transformation of a large shell in late ontogeny was diminished being achieved in that ontogeny. Variation be by chamber compression. Further, once the com tween populations from different regions com pressed design was established, the hydrome pounds the latter influence, with individuals chanical advantage may have led to its being from low latitudes commonly proceeding further selected for progressively earlier in ontogeny. A with compressive transformations than their suitable scenario for the initiation of these onto higher latitude counterparts. genetic changes may have been provided by the On the other hand, pattern in late ontogeny is lower Miocene climatic amelioration, which more stable in taxa in which the initiation of would have reduced the density of tropical water. major shape transformations have migrated back In axially compressed shells there may have been to mid-ontogeny. A picture of phyletic stasis is two complementary trends in late ontogeny. affected by long sequences of populations in Modifications to the spiral profile of chambers which adult morphology is relatively static be promoted the development of large shells; com cause transformations have occurred earlier in pression ofthe axial profile of chambers reduced ontogeny. FOHSELLA UNEAGE SHAPE CHANGE DURING ONTOGENY Chamber Width (W) FIGURE 38.—Plots of shell radius and chamber width (logarithmic data) in the ontogenies of specimens oi Fohsella (after Olsson, 1972, figs. 6-10). Commonly, shape change occurs about mid-ontogeny. Chamber width increases in a and d; shell radius increases in b and e. Increments in shell radius (by extension of chambers) is an important technique to achieve larger shell size in late ontogeny. Olsson (1972:174) noted an increase in the number of chambers in specimen e. This occurred partly by a decline in rate of width expansion (allowing more chambers per whorl) and partly by modest extension in total degrees of whorl in ontogeny. NUMBER 58 PATTERN WITHIN THE TREE the gradualist model focuses on transformations within lineages. In the following we review rele MODELS.—Eldredge and Gould (1972) pro vant features of Neogene globorotalid history foundly altered thinking about evolutionary de and, after consideration of population structure, velopment when they challenged the traditional try to assess their evolutionary mode. view of phyletic gradualism and argued that the GRADATIONAL VARIATION.—Commonly, fossil record indicated patterns of punctuated there is evidence of intergradation between suc equilibria. Following Darwin, paleontologists had cessive globorotalid taxa. Examples can be cited traditionally envisaged evolution as primarily from all lineages and often relate to extent of phyletic and involving gradual, progressive trans chamber compression and keel formation {Glo formations of entire ancestral populations. Long borotalia miozea-G. praemenardii; G. tosaensis-G. continued, unidirectional character trends were truncatulinoides; G. martinezi-G. margaritae; Foh interpreted, adaptively, as functional improve sella peripheroacuta-F. praefohsi). But there is also ments to a static, or gradually changing environ intergradation in taxonomic transitions based on ment. According to the new view, species do not introduction of other features (e.g., C-type cham change in a continuous, progressive fashion, but bers, G.praemenardii-G. menardii) and on undergo long periods of stasis during which mor changes in number of chambers per whorl (G. phological change is either nondirectional or of miocenica—G. pertenuis; G. puncticulata—G. in little consequence. Actual speciation occurs in flata). small, peripherally isolated populations and is Further, globorotalid histories are not char associated with rapid modification of morphol acterized by sudden appearances of novel archi ogy. Once the transformation is achieved, the tectures. Indeed, the lack of design discontinui new species expands, and another period of stasis ties has led biostratigraphers to base taxonomic follows under the new adaptive equilibrium that concepts on particular morphotypes. This is well has been forged. An extension to the argument demonstrated by Blow and Banner's (1966) re is that selection within lineages occurs at the vision of Fohsella in which taxa were defined species level (Stanley, 1979:186-195) and that using stages in keel development around the last the process of speciation is decoupled from pop whorl (rounded periphery throughout, F. peri ulation dynamics. pheroronda; acutely angled periphery on last Punctuational evolution should leave a distinc three chambers, F. peripheroacuta; keel on last tive stratigraphic record. The theory postulates three chambers, F. praefohsi; keel on all chambers that founder populations are so small and the of outer whorl, F. fohsi). Several of these taxa morphological transformation so rapid that no were shown as contemporaries. Biostratigraphic trace of the change is likely to be preserved. information was extracted by carefully defining Effectively a "revolution on a bedding plane" is variants that appeared successively in an inter- hypothesized and recovery of connecting links grading continuum. The example is important. between ancestors and descendants is improba The pattern (Figure 2) is depicted as step-like ble. Morphological discontinuities are to be ex and might be viewed as punctuational. Only pected and the stratigraphic record will provide when the nature of the "taxa' is considered is it a poor guide to ancestry. obvious that the pattern is not that of a set of The models are of particular interest to paleo- discrete species. Architectural change in Fohsella biologists because ofthe contrasting stratigraphic is a typical example of globorotalid chamber records that they should generate. Potentially, compression and keel construction. It took place evolutionary mode may be identified from fossils. over a period of 1-1.5 m.y. and apparently in Note, however, that the models are not strictly volved continuous transformations and a spec alternatives. The punctuational model focuses on trum of morphotypes like those in Globorotalia speciation and lineage divergence. In contrast, miozea-G. praemenardii, and in G. ronda—G. 82 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY truncatulinoides. Still longer trends, some extend sella occupied over I m.y. These latter examples ing over a period of about 8 m.y., have been relate to rates of major architectural transfor mapped by Malmgren and Kennett (1981) in a mation within lineages. While they are unaccept- study of the origin of G. inflata. ably slow in terms of the punctuational model, While some globorotalid taxa are certainly "ve they do not directly confront it. hicles of biostratigraphic convenience," far re Yet the scene, generally, is not one of contin moved from the biological species concept, con ued redesign throughout the history of a lineage. tinuity of variation between ancestor and descen Chamber compression and keel development dant is characteristic of most lineages. The prob were finite, delimitable episodes and were usually lems it has presented to biostratigraphers are followed by extended periods of relative stasis apparent when the high resolution data of Malm without further developments in the form of gren and Kennett (1981) are considered. We adult shells. Variations among Globorotalia conoi contend that the variation pattern (vertically) in dea populations arose in its 8 m.y. history, but globorotalid lineages is much closer to the grad architectural innovations comparable with those ualist model than to the punctuational. of chamber compression and keel formation did TEMPO OF CHANGE.—Phyletic evolution is not develop. The G. menardii-G. cultrata lineage usually represented as involving long-term has an even longer history (15 m.y.) in which the trends, whereas the punctuational model envis basic discoidal shell form did not alter. Note that ages rapid transformations, certainly on geolog ontogenetic strategy influences the pattern of ical scales (thousands of years at most; Gould, variation perceived. Predisplacement of keel de 1980). Much recent attention has therefore been velopment to progressively earlier stages results focused on tempo. As expected, there is a wide in stable "adult" morphology, although earlier spectrum of rates, and no simple demarcation formed chambers may still be undergoing trans between the models on this basis is available. formation. Further, morphological stasis was not Transformations in speciation events of up to confined to lineages that followed the chamber 50,000 years have been accepted as punctua compression-keel formation trend to its conclu tional (Williamson, 1981). Nevertheless, even sion. Globorotalia scitula is a good example. It this duration appears to be about the lower limit never progressed to the keeled stage and has of the globorotalid data. This is represented by retained its moderately compressed architecture an estimate of 50,000 years for the spread of the for about 12 m.y. keel around the chambers of the outer whorl of The data on rates of change and on duration Globorotalia truncatulinoides (Berggren, 1969; of particular architectures illustrate well the view Figure 39c). However, this is a partial estimate that globorotalids pursued strategies that seldom of the time taken for keel development as it conform closely to either model. There are ex neglects evolution of the earliest stages of the tended episodes of transformation far exceeding structure. Loss of the keel during the origin of the durations envisaged in the punctuational G. puncticulata also seems to have occurred rel model. There are also some long, gradual clines. atively rapidly (estimated as 0.09-0.27 m.y. by Yet, there are taxa that retained a basic design Scott, 1982, and as 0.48 m.y. by Malmgren and for extended periods. The most significant gen Kennett, 1981). The inception ofthe keel in the eralizations are that bedding-plane revolutions in G. praescitula plexus represents a much longer morphology are absent and that rates of evolu period. In the Southwest Pacific the first weak tion were sluggish. folds appeared with Zone N8. It was not until POPULATION STRUCTURE AND VARIATION.— upper N12 or N13 (over 3 m.y. later) that the The distribution, size, and number of constituent structure was fully developed and fixed in the populations representing a taxon and their de phenotype. Comparable transformations in Foh gree of intercommunication are likely to signifi- NUMBER 58 83 G. CONOIDEA - G. INFIATA G. PUNCTICULATA G. TEUNCATUUNOIDES 1.7-, m.y 1M ^SSfe MEAN CHAMBERS OUTER WHORL PROPORTION KEELED SPECIMENS KEEL DEVELOPMENT FIGURE 39.—Rates of morphological transformation in globorotalids: a. Long-term (upper Miocene-Quarternary) decline in number of chambers in the outer whorl of Globorotalia conoidea and a descendant lineage (G. inflata) at DSDP Site 284 (after Malmgren and Kennett, 1981, fig. 2; the envelope includes 95% confidence limits). This trend probably occurred throughout temperate watermasses in the Southern Hemisphere. The upper Miocene segment has not been identified in Northern Hemisphere populations, b. Relatively rapid regression of the keel during the divergence ofthe G. inflata lineage from G. conoidea (after Scott, 1982, fig. 9). Polymorphic populations (G. puncticulata sphericomiozea), with the keel in various stages of reduction, progressively became dominated by completely nonkeeled individuals {G. puncticu lata puncticulata) in the lower Pliocene. The decline in keeled specimens (including those in which the keel has lost its topographic expression and is reduced to a moderate thickening of the wall at the periphery, Scott, 1982, fig. 8e-f) is shown as a proportion (envelope includes 95% confidence limits). The data are from a shallow, landward sequence at Kapitea Creek, New Zealand. In the oceanic sequence to the west at DSDP Site 284, Malmgren and Kennett (1981, fig. 2) recorded an oscillatory decline, c. Development of the keel in the evolution of G. truncatulinoides (after Berggren, 1969, text-fig. 3; data from Chain Station 61-171, subtropical North Atlantic, further data in Berggren and others, 1967). The typical globorotalid phyletic pattern is followed in which the keel originates on chambers formed at the conclusion of ontogeny and, subsequently, appears progressively earlier in the ontogenetic sequence. Figure 24 shows a specimen (sub-Recent) in which the keel occurs in the middle whorl. Predisplacement of the keel in G. truncatulinoides occurred more rapidly than in the G. praescitula plexus where several million years elapsed before the keel became established around the other whorl in all individuals. cantly influence evolutionary patterns. common with other members of the plankton Recent taxa provide the best guide to the (McGowan, 1971; Zeitzschel, 1978), some plank nature of globorotalid populations. Most are very tonic foraminiferal distributions are related to widely distributed (Figure 31) but exhibit signifi watermass boundaries (Berger, 1969), although cant regional variation, especially in the equato there is considerable expatriation of individuals. rial-polar direction. Is there evidence that species If watermass boundaries are significant in de are partitioned into populations? As a first ap fining the limits of species distributions, they proximation, watermasses may impose a popula might be expected to partition widely distributed tion structure on globorotalid taxa. Planktonic taxa. The existence of such a population struc foraminifera are involuntary travellers and cir ture might be revealed in patterns of shell vari culation is more regular and better defined ation. Studies of variation in Globorotalia trun within, rather than between, watermasses. In catulinoides are relevant because of its wide lati- 84 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY tudinal distribution. Kennett (1968) did not con stressed. There is a high probability of reincor sider watermass distributions directly, but the poration. When this occurs the subpopulation clinal relation he envisaged between shell form loses its shelter and is likely to be submerged by and temperature suggests that population struc the large parent population. McGowan (1971:54) ture is indistinct. Similarly, Lohmann and Malm noted that isolates in the Kuroshio and California gren (1983) did not discover shape changes about currents are rather quickly extinguished. There a watermass boundary. However, in a detailed is no suggestion in the foraminiferal literature of study of a latitudinal transect (Figure 40), Healy- the formation of very small subpopulations that Williams (1983) recognized two shape families might be effective in evolutionary processes. whose distributions were related to watermass In review, although data on the structure of patterns. A third family occurred in a wide zone globorotalid populations are woefully inade of mixing adjacent to an intervening boundary quate, the following features possibly apply: (1) (subtropical convergence). Taxa are probably composed on a few, large, For a widely distributed species, watermass populations weakly defined by watermass distri divisions would create geographically extensive butions (intrapopulational structure and actual populations. A hypothetical taxon distributed be deme sizes are quite unknown). (2) Populations tween about 50 °N to about 50 °S in the Pacific are usually contiguous; population boundaries might be divided into 7 populations on the basis are dynamic and partial (Figure 40), so that in- of present day watermass divisions (Bradshaw, terpopulation communication can occur. (3) Iso 1959, fig. 4). Potentially, population sizes might lation of very small subpopulations, either on the be very large. Abundances of one globorotalid margins, or within watermasses due to patchi per cubic meter occur in surface water (Tolder- ness, seasonal fluctuations, or physical factors, is lund and Be, 1971, table 4). At this density, a for limited periods (several months at most, per small watermass dimensioned 1200 km by 500 haps for no more than 5 globorotalid genera km would carry 10'^ individuals. Certainly, this tions) and is likely to be followed by their rein estimate is very crude. It neglects the vertical corporation into the parent population. distribution of species (likely to be significant in deep dwelling globorotalids), age structure, sea Evaluation sonality, and patchiness (Phleger, 1951:31; Hem leben and Spindler, 1983:144). Nevertheless, it Several aspects of globorotalid history must be provides an indication of magnitudes. taken into account in an evaluation of their evo While the watermass hypothesis suggests that lutionary mode: (1) Within lineages, episodes of globorotalid populations are likely to have been chamber and shell redesign were usually pro very large, an important question is whether tracted (sometimes over 1 m.y.) and left a good small isolates could form. This is especially rele record of gradationally changing populations. (2) vant to the punctuational model as it is part of While there were large transformations, phylet the modus operandi of rapid evolutionary ad ically, within lineages, major branching occurred vance. Eddies often become detached from the in most; divergences were not abrupt. (3) Archi major gyres for several months and would pro tectural stasis developed, notably in taxa that vide the opportunity for several generations of a developed out of episodes of chamber compres small subpopulation of a planktonic taxon to be sion. expatriated and for architectural transforma The structure, size, and extent of intercom tions to be initiated. Within watermasses, patch munication between globorotalid populations iness and seasonal fluctuations might lead to the were possibly major determinants of their evo isolation of small subpopulations. However, the lutionary pattern. Consider the tempo of change. very temporary existence of such entities is The design revolutions of the punctuational NUMBER 58 85 GLOBOROTALIA 7JIUNCAWLIH0IDES HARMONIC 2 HARMONIC 3 SHAPE VARIATION rN SOUTHERN INDIAN OCEAN JZI .08 .20 .0^ .17 I —I FIGURE 40.—Shape analysis of axial outlines oi Globorotalia truncatulinoides in core top samples from the southern Indian Ocean (after Healy-Williams, 1983, figs. 1, 3). Distributions and means (vertical markers) of normalized amplitudes are shown. Harmonic 2 represents elonga tion of the outline. Harmonic 3 represents a trefoil which, in G. truncatulinoides, is influenced by the ventral elongation of the shell. Reconstructions of a particular outline generated by harmonics 1-2 and 1-3 (Healy-Williams and Williams, 1981, fig. 2) are shown at the head of the histograms. Southernmost samples from the subpolar watermass are elongated and very weakly conical. Adjacent to the subtropical convergence there is still marked elongation, but conical shape is stronger. North of the subtropical convergence shells maintain or increase their conical shape, but elongation diminishes (this is related to change in coiling direction). The watermass boundary is within a broad zone of shape transformation between the typical central watermass morphotype and the subpolar morphotype. A conical specimen (upper left), typical of the central watermass, and the holotype (lower left), of G. truncatulinoides malvinensis (56°S, South Atlantic; Boltovskoy and Watanabe (1981, pi. 3: fig. Ic) are illustrated. 86 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY model require small, fully isolated subpopula tions (Figure 41). Although Lande (1980) dis counted the effectiveness of Mayr's founder prin ciple, he still suggested that, under selection in tensities of a few percent, only a few hundred to a few thousand generations might be required for the origin of a new phenotype in small, iso lated populations. Perhaps about 1000 years FIGURE 42.—Evolutionary mechanisms in which multidi might be required for 10,000 generations of a mensional genotypes are represented by two dimensions and planktonic foraminiferal species. Small, local the adaptive topography for gene frequencies is portrayed populations are also an important component in by fitness contours: a, a large panmictic population is shown Wright's (1932, 1982) shifting balance theory. responding to changing conditions (after Wright, 1932, fig. 4c). The selective peak has moved to (-(-). The readapting This is a model for phyletic evolution. The taxon population (shaded) is shown moving from the old location is divided into small, partially isolated popula- (X) towards the new peak, b, a species is divided into many small, partially isolated, populations (after Wright, 1932, fig. 4f). There is trial and error exploration of the adaptive AttOPATRIC SPECIATION topography. The variability of the species is magnified by differentiation of populations and the influence of selection PERIPHERAL ISOLATE MODEL DUMB-BELL MODEL is aided by diffusion from the superior populations. Some populations have moved (by genetic drift) from one adaptive peak (-1- upper left) and have crossed a saddle to a higher peak (-1- lower right). Eventually, others should follow. EXPANSION OF RANGE tions (Figure 42), which are envisaged as probing the adaptive landscape for higher optima. A local population that has been moved off its present peak by random drift in gene frequencies may find its way to higher adaptive territory, for example, via the introduction of a novel feature ISOLATION that improves functionality. If this occurs, and there is sufficient diffusion to its neighbours, all populations will eventually follow the leader to wards the new adaptive peak. The effectiveness of the process is controlled by the amount of LARGE PANMICTIC POPULATION genetic drift, selective pressures, population size, FIGURE 41.—Allopatric speciation models (after Bush, 1975, and intercommunication. Templeton (1982) figure 1). Right, Dumb-bell model; a widespread species is gives an excellent physical analogy of the inter divided into two relatively large populations by an extrinsic play between drift and selection in this process. barrier. Gene flow is interrupted and the populations accu Globorotalid populations do not appear to mulate genetic differences as they respond to differing se lective pressures. Differences in genotype so built up may have the structure required by these models. result in hybrids being selected against should the popula Neither the extent of isolation required by the tions re-establish contact. Eventually, reproductive isolation punctuational model nor the fine partitioning of may occur. Left, Peripheral Isolate model: A few individuals, the shifting balance model is indicated by present perhaps remnants of a population "flush" that has penetrated knowledge of modern populations. The very beyond the normal environment of the species, attempt to large population sizes of modern taxa, perhaps exploit a new habitat, isolated from the parent population. Individuals from semi-isolated peripheral populations are with panmixus over large regions, suggests that best suited to be preadapted as colonists and also may tend models based on changes in small populations towards inbreeding. Speciation may occur rapidly. are unlikely to have operated in globorotalid NUMBER 58 87 evolution. The distinctly sluggish rates of evolu would be necessarily slow in very large popula tion we have noted thus seem to support the tions (rate of genetic change tends to be inversely inferences about population characteristics. In proportional to population size), followed the short, the population structure to allow rapid progress of the environmental trend. The trend evolution was not available. A similar argument reducing the number of chambers in the outer was advanced by Brinton (1962:244) concerning whorl of G. conoidea-G. inflata (Figure 39a) may the evolution of crustacean zooplankton. be a comparable upper Miocene-Pliocene exam Stasis in morphology for the greater part of ple of a long, environment-driven morphocline. species histories is an important prediction of the While both stasis and long term transforma punctuational model. Stasis is also an important tions in globorotalid histories may have resulted feature of the globorotalid pattern. Mayr from selection variously acting on large popula (1963:542) and Eldredge and Gould (1972:114) tions, mechanisms of branching require a differ attributed phenotypic stability to genetic hom- ent perspective. Cessation of gene flow is a pre ostasis (the tendency for a population to return requisite for divergence, yet the ocean is an to its original state following perturbations). In efficient mixer; globorotalid populations were this view, genetic structure acquired by the pe probably large, contiguous, and only weakly iso ripheral isolate is retained thereafter. But does lated. How could they become disjunct? We must stasis uniquely identify the operation ofthe punc exclude from consideration purely genetic mech tuational model? Lande (1980) questioned the anisms (Templeton, 1980), because of the ab significance of homostasis and argued that phe sence of data. notypic stasis is primarily maintained by stabiliz Geographic separation of populations can be ing selection. In one of Wright's models (1932) brought about by the emergence of barriers be stasis is shown to develop in a panmictic, popu tween oceans. This allows the dumb-bell model lous taxon (occupying a relatively stable habitat), (Figure 41) to operate. Some menardine taxa which, having climbed an adaptive peak, is kept (Figure 15) that evolved in the Pliocene are there by selection. The Globorotalia menardii-G. largely confined to the Caribbean and tropical cultrata group may be an example of this condi Atlantic (Parker, 1973:267; Bolli and Krashen tion. It is widespread, populous, and of consid innikov, 1977). The truncated history of Globor erable longevity (nearly 15 m.y.) The tropical otalia pertenuis in a Pacific sequence adjacent to environment in which it lives has probably had Central America was considered by Keigwin the most stable climatic history of those occupied (1982) to be due to the increasing effectiveness by globorotalids. of the emerging Panama Isthmus as a barrier. Gradual evolution in large populations via However, the role of this barrier in the Pliocene mass selection can be envisaged as a tracking menardine speciations is yet to be established process. Environmental changes effectively alter clearly. All of these taxa seem to have arisen in the selective topography of a taxon (Figure 42). the Caribbean-tropical Atlantic and, although G. If these changes are directional even populous menardii (a probable ancestor) was largely ex taxa will tend to track the movement of the cluded, Bolli and Krasheninnikov (1977) re adaptive peak they previously occupied. The corded its continued presence in one sequence early to middle Miocene increase in surface tem in that region. Probably, the emerging isthmus peratures was prolonged and directional (Figure served only to partially isolate the Caribbean- 33) and altered important physical parameters tropical Atlantic populations from those of the (e.g., density of surface water). This scenario may Indo-Pacific. have been responsible for the evolutionary pat Watermass movements in response to temper tern in the Globorotalia praescitula plexus and ature oscillations might also isolate populations Fohsella, which culminated in the axially com (Brinton, 1962:246; McGowan, 1971:54). In the pressed design. Possibly rates of evolution, which Southern Hemisphere, northward expansion of SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY cool temperate watermasses would isolate Pacific might serve as possible blueprints for future spe and Atlantic populations of warm temperate cies (Pierrot-Bults and van der Spoel, 1979:166). taxa. Expansion of the area of warm temperate Further, some divergences (e.g., Globorotalia water would re-establish contact. This scenario menardii, G. puncticulata, G. truncatulinoides) are might allow operation of the dumb-bell model, regionally represented by widely varying popu particularly after the Miocene, when the mid- lations, which include innovative as well as ances latitude climatic regime was oscillatory. Al tral architectures. They may indicate broad though various speciations are recorded from zones of contact between populations responding this period in the Southern Hemisphere (e.g., to different selection pressures. The seemingly Globorotalia puncticulata; Scott, 1982), there are slow tempo of divergence (as in G. menardii) still insufficient biogeographic data to judge the would be compatible with the large populations importance of this mechanism. involved. While full allopatry would arise only in special Analysis of speciation from biostratigraphic circumstances, parapatric speciation develops data is highly constrained by the degree of stra from partial isolation of populations particularly tigraphic resolution and the availability only of those varying clinally, and thus aligns with a broad geographic and stratigraphic patterns. major feature of globorotalid distributions. It can Bush (1982:128) observed that even the current be implemented by divergent selective pressures models "are little more than speculation based operating on populations in different habitats. on the subjective interpretation of equivocal While the previous discussion of variation in data." Carefully contrived sampling ofthe record Globorotalia truncatulinoides (Figure 40) focused might point to the operation of differential selec on the significance of a watermass boundary, the tion pressures, which are an important compo broad geographic pattern in the data is one in nent ofthe parapatric model. It might also detect which morphological separation increases with extrinsic factors (e.g., oceanographic) that facili distance. The same feature shows in an analysis tate reproductive isolation. But intrinsic genetic of axial shape in G. conoidea and relatives (Figure factors are also significant in parapatric specia 43). Morphometrically, the closest neighbors to tion (Endler, 1977:142-151; Barton, 1980), and, Mediterranean samples are from the South At as yet, their operation in globorotalid popula lantic; in turn, these are closest to New Zealand tions is quite unknown. In review, allopatric spe samples. ciation might occur in globorotalids when special Several data favor the operation of parapatric geographic or oceanographic patterns arose. We speciation in globorotalids. Polytypic taxa are have not identified good examples. This is also common and their variation often has a signifi true of parapatric speciation, but there are cer cant clinal component. As judged from mor tainly factors in globorotalid population struc phology (Figure 40) populations in contiguous ture and distributions (modern and fossil) that watermasses appear to be locally adapted and favor its operation. Retrospect There has been considerable research on Neo The origins of several lineages are still quite gene globorotalids but as this survey suggests obscure. This applies not only to the lower Mio very significant gaps remain in our knowledge cene founders but also to later plexi, such as about their history, biogeography, and evolution Globorotalia crassaformis and G. scitula. Popula ary strategies, as well as about the functional tion sequences (comparable to those within the significance of shell form. Some of these prob radiation) to show transformation series between lems and possible lines of research into their paragloborotalids and primitive globorotalids solutions, are emphasized below. have not been documented. Earliest populations NUMBER 58 89 REGIONAt VARIATION IN AXIAt SHAPE: GLOBOROTAUA CONOIDEA, G. MEDfTERRANEA, MiH G. INFLATA UNEAGE sphericomiozea _™^ sphericomiozea conoidea I \ conoidea (conomiozea morphotype} -?€?/'M, infiata c^^'^' puncticulata advanced S. Atlantic Meditarranun \ / mediterranea puncticulata Naw Zealand conoidea type FIGURE 43. Regional variation in axial shape oi Globorotalia conoidea, G. mediterranea, and G. inflata lineage (mean axial outlines, plotted to a common scale, are derived from digitized samples of 27 to 52 specimens). Specimens in which the last-formed chamber was smaller than the penultimate were excluded. The graph shows the disposition of samples in a canonical analysis of 15 normalized Fourier harmonic amplitudes. LI, L2 account for 81% of total variation; circles give approximate 95% confidence limits for means. Upper Miocene samples from the South Atlantic (CH507, CH704) occupy an intermediate position between a New Zealand (J32/f44) and Mediterranean collections (JT1911 A, JT1931). Morphometric distances among these samples reflect the amount of geographic separation. N98/f 565 is from an older (middle Miocene) horizon, near the entry of G. conoidea. S51/f779 represents a population in which the Southwest Pacific ventroconical conomiozea morphotypes are common. In contrast, Pliocene samples of G. puncticulata sphericomiozea (CH404, J32/f90, P29/f55), G. puncticulata puncticulata (CH207, P29/f71), and G. inflata (P29/fl41) from the South Atlantic and New Zealand show a common trend towards increasing globosity, and regional differences are not obvious. (Sample details are given in Scott, 1983.) 90 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY may have been small and localized. However, ance on morphological relationships. We think from present data it is premature to conclude that the density of much ofthe record of lineages, that globorotalid origins are beyond the resolu the relatively slow rate of character evolution, tion ofthe stratigraphic record. Like G. incognita, and the absence of very rapid speciation events some founders may have closely resembled an permits the biostratigraphic approach. Further cestral paragloborotalids. As yet, neither has the more, the stratigraphic position of some taxa record been adequately searched nor has varia have been subject to considerable testing because tion in primitive globorotalids and paragloboro of their use in biostratigraphic zonal classifica talids been sufficiently mapped. tions. Phyletically, these provide historical ref Our assessment, mainly from comparative erence points. The order of taxa in lineages, morphology but supplemented from strati established from biostratigraphy, corresponds graphic distributions, is that Neogene globoro excellently with observed character trends. No talids are polyphyletic. This applies both to lower instance of the alleged bete noire of phyletic re Miocene founders and later plexi originating in construction from biostratigraphy (ancestors, as the upper Miocene and Pliocene. The implica judged from comparative morphology, appear tions of such a history for classification have yet ing in the record subsequent to descendants) was to be satisfactorily resolved. Biostratigraphers found. Advanced taxa (in terms of chamber com (Jenkins, 1971; Kennett and Srinivasan, 1983) pression and keel development) in a lineage are have used Globorotalia as a form genus and iden always preceded in the record by less advanced tified lineages by subgenera. This procedure is populations. In Fortey and Jefferies (1982) term, an uneasy amalgam of horizontal and vertical the globorotalids have a "high" record. It is likely classifications. For the globorotalids it suggests that many taxa are preserved for much of their that they are a group of closely related lineages. real ranges and that the stratigraphic tree will We consider that many similarities among line eventually be a good approximation to the cor ages are the result of repetitive trends and do rect phyletic tree. not indicate phyletic relationship. As a unit of While we argue for a biostratigraphic ap phyletic classification, Globorotalia possibly proach to the assessment of phylogeny, there are should refer only to the Globorotalia praescitula a number of specific problems of lineage mem plexus with subgenera identifying its branches bership and relations to be resolved from closer (e.g.. Pliocene menardines, G. inflata lineage). sampling of the record and studies of population Once established, the major lineages left ex variation: (1) Is Globorotalia zealandica part of tensive, high resolution records. We argue that, the G. praescitula plexus? (2) There are various in piecemeal fashion from section to section, problems with the Globorotalia tumida lineage: most of their histories can be traced from the discrimination from coeval menardine taxa at preserved populations. If these are sampled at various stages of ontogeny; discrimination of G. sufficient density they are likely to provide a merotumida from G. plesiotumida; interpretation sequence of overlapping variation fields. The of the morphological hiatus between these taxa primary example of quantitative documentation and supposed ancestors (G. lenguaensis and G. of lineage history is by Malmgren and Kennett paralenguaensis). (3) Connection between Globor (1981). We suspect that the record they por otalia gigantea and G. scitula and their relation trayed is representative of the radiation and ex with G. praescitula plexus. (4) Relationships ceptional only in its continuity at one site. More among upper Miocene scituline taxa; are there documentation of this sort is required to better several lineages? (5) Origin of the Globorotalia establish relationships. crassaformis plexus; relationship of G. crassula to A phyletic tree derived from biostatigraphic the plexus. evidence is decried by those who advocate reli The outstanding feature of the radiation is NUMBER 58 91 that a few, simple architectural trends were pur biogeographic and paleoenvironmental data sued in common by separate lineages. To cladists should help to resolve the relation between clines the latter assertion will seem to be weakly sup in morphology and environmental trends. The ported. But the likelihood of strong convergence evolution of ocean climate and structure was within the radiation is certainly strengthened by possibly the engine of Neogene globorotalid ev the impressive resemblances with earlier radia olution, but the connection has been surmized tions that lacked direct connections with the Neo rather than established. A potential for circular gene. Some similarities between taxa from dif reasoning exists, however, because paleoceano ferent radiations (e.g., compressed discoidal graphic inferences partially rest on interpreta shells of Paleogene and Neogene) are as close as tions of evolutionary innovations. those within a single Neogene lineage. However, Despite the current vogue ofthe punctuational while biostratigraphy echoes convergence, it is model, mechanisms of speciation and divergence much more difficult to decode explanations of are still poorly understood. Abrupt appearances architectural form from this source. Ofthe major of new globorotalids are not typical. Divergences designs only the menardine shows a distinctive are represented by gradational transformations, paleobiogeographic pattern to which shell form which particularly involve modifications to cham can be related. We have found few clues from bers formed late in ontogeny. The question re paleobiogeography about the functionality of mains as to how population disjunction, life his other shell designs. Input from studies on living tory, and environment are interrelated. The bio globorotalids is required. "Cost benefit" analyses geographic patterns of bifurcating populations of various shell shapes are but one approach. A and the way in which genetic isolation was estab broad spectrum of data is needed, ranging from lished are unknown. The very nature of the feeding patterns, through the role of the smooth planktonic environment poses severe difficulties globorotalid wall in life processes, to the signifi for allopatric speciation through small, isolated cance of vertical migrations and occupancy of populations. Some indirect evidence favors par bathypelagic environments. Ontogenetic data apatric rather than allopatric speciation, but we are likely to be very important: recall the size lack good examples of either process. The fossil (age) related changes in chamber form that are record lacks sufficient temporal resolution for so prominent during growth of globorotalid highly refined analyses of speciation. Further, it shells. is biased towards the successful and provides only In evolutionary studies the biostratigraphic lit some of the clues about speciation mechanisms. erature may be misleading because some taxa are Understanding of variation, structure, distribu arbitrarily defined intrapopulational morpho tion, and communication of modern populations types and range charts suggest abrupt taxic tran will provide others. Are there short-term exper sitions. However, inspection of character trans iments? Are most submerged by the parent pop formations indicates that the tempo of phyletic ulation? How do they achieve isolation initially? change within lineages was slow and represented If some of these questions can be resolved, inter by long sequences of intergrading populations. pretation of patterns in the fossil record will be Studies of shell variation integrated with paleo advanced. Literature Cited Alberch, P., S.J. Gould, G.F. Oster, and D.B. Wake Be, A.W.H., C. Hemleben, O.R. Anderson, M. Spindler, J. 1979. Size and Shape in Ontogeny and Phylogeny. fa- Hacunda, and S. Tuntivate-Choy /^oftio/ogy, 5(3):296-3l7. 1977. Laboratory and Field Observations of Living Anderson, O.R., and A.W.H. Be Planktonic Foraminifera. Micropaleontology, 1976. The Ultrastructure of a Planktonic Foraminifer, 23(2):155-179. Globigerinoides sacculifer (Brady) and Its Symbiotic Berger, W.H. Dinoflagellates.yourna/ of Foraminiferal Research, 1969. Ecologic Patterns of Living Planktonic Formini- 6(1):1-21. fera. Deep-Sea Research, 16(1): 1-24. Arkell, J. 1971. Sedimentation of Planktonic Foraminifera. Ma 1933. The Jurassic System in Great Britain. 681 pages. rine Geology, 11(5):325-358. Oxford: Clarendon Press. Berger, W.H., and DJ.W. Piper Banner, F.T., and W.H. Blow 1972. Planktonic Foraminifera: Differential Settling, 1959. The Classification and Stratigraphical Distribu Dissolution, and Redeposition. Limnology and tion of the Globigerinacea. Paleontology, 2(1):1- Oceanography, 17(2):275-287. 27, plates 1-3. Berger, W.H., E. Vincent, and H.R. Thierstein 1965. Progress in the Planktonic Foraminiferal Biostra 1981. The Deep»-Sea Record: Major Steps in Cenozoic tigraphy of the Neogene. Nature, 208(5016): Ocean Evolution. Society of Economic Paleontologists 1164-1166. and Mineralogists Special Publication, 32:489-504. Barbieri, F. Berggren, W.A. 1971. Comments on Some Pliocene Stages and on the 1966. Phylogenetic and Taxonomic Problems of Some Taxonomy of a Few Species of Globorotalia. L'A- Tertiary Planktonic Foraminiferal Lineages. Vo- teneo Parmense, Acta Naturalia, 7(l):3-24. prozyi Mikropaleontologii Akademiya Nauk, SSSR, Bartlett, G.A. 10:309-332. [In Russian.] 1968. Mid-Tertiary Stratigraphy of the Continental 1969. Rates of Evolution in Some Cenozoic Planktonic Slope off Nova Scotia. Maritime Sediments, Foraminifera. Micropaleontology, 15(3):351-365, 4(1):22-31, plates 1-3. figures 1-13. Barton, N.H. 1977. Late Neogene Planktonic Foraminiferal Biostra 1980. Multilocus Clines. Evolution, 37(3):454-471. tigraphy of the Rio Grande Rise (South Atlantic). B6, A.W.H. Marine Micropaleontology, 2(3):265-313, plates 1- 1969. Planktonic Foraminifera. In V.C. Bushnell and 4. J.W. Hedgpeth, editors. Distribution of Selected 1981. Correlation of Atlantic, Mediterranean and Indo- Groups of Marine Invertebrates in Waters South Pacific Neogene Stratigraphies: Geochronology of 35°S Latitude. Antarctic Map Folio Series, folio and Chronostratigraphy. In N. Ikebe, M. Chiji, R. 11:9-12. New York: American Geographical So Tsuchi, Y. Morozumi, and T. Kawata, editors. ciety. Proceedings oflGCP 114: International Workshop on 1977. An Ecological, Zoogeographic and Taxonomic Pacific Neogene Biostratigraphy, Osaka, 1981, pages Review of Recent Planktonic Foraminifera. In 29-60. Osaka: Osaka Museum of Natural History. A.T.S. Ramsay, editor. Oceanic Micropaleontology, 1984. Neogene Planktonic Foraminiferal Biostratigra 1:1-100. London: Academic Press. phy and Biogeography: Atlantic, Mediterranean 1980. Ontogenetic Calcification in a Spinose Planktonic and Indo-Pacific Regions. In N. Ikebe and R. Foraminifer, Globigerinoides sacculifer (Brady). Tsuchi, editors. Pacific Neogene Datum Planes, Marine Micropaleontology, 5(3)283-310, plates 1- IGCP Project 114, pages 111-161, figures 1-15. 9. Tokyo: University of Tokyo Press. Be, A.W.H., and J. van Donk Berggren, W.A., and M. Amdurer 1971. Technical Comments on A.D. Hecht's and S.M. 1973. Late Paleogene (Oligocene) and Neogene Plank Savin's "Oxygen-18 Studies of Recent Planktonic tonic Foraminiferal Biostratigraphy of the Atlan Foraminifera." 5dmc^, 173(3992): 167-168. tic Ocean (Lat. 30 °N to Lat. 30°S). Rivista Ital- 92 NUMBER 58 93 iana di Paleontologia e Stratigrafia, 79(3):337-392, Leiden: E.J. Brill. [Volumes 1 and 2 text; volume plates 25-33. 3, plates.] Berggren, W.A., M.P. Aubrey, and N. Hamilton Blow, W.H., and F.T. Banner 1983. Neogene Magnetobiostratigraphy of Deep Sea 1966. The Morphology, Taxonomy and Biostratigraphy Drilling Project Site 516 (Rio Grande Rise, South of Globorotalia barisanensis Le Roy, Globorotalia Atlantic). In Initial Reports ofthe Deep Sea Drilling fohsi Cushman and Ellisor, and Related Taxa. Project, 72:675-713, plates 1-5. Washington, Micropaleontology, 12(3):286-302, plates 1-2. D.C: National Science Foundation. Boersma, A., and N.J. Shackleton Berggren, W.A., and B.U. Haq 1977. Tertiary Oxygen and Carbon Isotope Stratigra 1976. The Andalusian Stage (Late Miocene): Bio phy, Site 357 (Mid Latitude South Atlantic). In stratigraphy, Biochronology and Paleoecology. Initial Reports of the Deep Sea Drilling Project, Palaeogeography, Palaeoclimatology, Palaeoecology, 39:911-924. Washington, D.C: National Science 20(l/2):67-l 29, plates 1-13. Foundation. Berggren, W.A., J.D. Phillips, A. Bertels, and D. Wall Boersma, A., N.J. Shackleton, M. Hall, and Q. Given 1967. Late Pliocene-Pleistocene Stratigraphy in Deep 1979. Carbon and Oxygen Isotope Records at DSDP Sea Cores from the South-Central North Atlantic. Site 384 (North Atlantic) and Some Paleocene Nature, 216(5112):253-255. Paleotemperatures and Carbon Isotope Variations Berggren, W.A., and R.Z. Poore in the Atlantic Ocean. In Initial Reports ofthe Deep 1974. Late Miocene—Early Pliocene Planktonic Fora Sea Drilling Project, 43:695-717. Washington, miniferal Biochronology: Globorotalia tumida and D.C: National Science Foundation. Sphaeroidinella dehiscens Lineages. Rivista Italiana Bolli, H.M. di Paleontologia e Stratigrafia, 80(4):689-698, fig 1950. The Direction of Coiling in Some Globorotaliidae. ures 1-3. Contributions from the Cushman Foundation for For Bermudez, P.J. aminiferal Research, l(3/4):82-89. 1949. Tertiary Smaller Foraminifera of the Dominican 1957. Planktonic Foraminifera from the Oligocene-Mio Republic. Cushman Laboratory for Forminiferal Re cene Cipero and Lengua Formations of Trinidad, search Special Publication, 25:1-322, plates 1-26. B.W.I. In A. R. Loeblich, Jr., and collaborators, Bermudez, PJ., and H.M. Bolli Studies in Foraminifera. United States National 1969. Consideraciones sobre los sedimentos del Mioceno Museum Bulletin, 215:97-123, plates 22-29. medio al reciente de las costas central y oriental 1967. The Subspecies of Globorotalia fohsi Cushman and de Venezuela. Boletin de Geologia (Venezuela), Ellisor and the Zones Based on Them. Micropa 10(20): 137-223, plates 1-18. leontology, 13(4):502-512. Bizon, G., and G. Glagon Bolli, H.M., and V.A. Krashenninikov 1978. Morphological Investigations on the Genus Glo 1977. Problems in Paleogene and Neogene Correlations borotalia from Site 372. In Initial Reports of the Based on Planktonic Foraminifera. Micropaleon Deep Sea Drilling Project, 42(l):687-707, plates 1- tology, 23(4):436-452. 12. Washington, D.C: National Science Founda Bolli, H.M., and J.B. Saunders tion. 1982. Globorotalia mayeri and Its Relationship to Globor Blank, R.G. and S.V. Margolis otalia siakensis and Globorotalia continuosa. Journal 1975. Pliocene Climatic and Glacial History of Antarc of Foraminferal Research, 12(l):39-50, plates 1-4. tica as Revealed by Southeast Indian Ocean Deep Boltovskoy, E. Sea Cores. Geological Society of American Bulletin, 1969. Living Planktonic Foraminifera at the 90 °E Me 86(8): 1058-1066. ridian from the Equator to the Antarctic. Micro Blow, W.H. paleontology, 15(2):237-255. 1959. Age, Correlation and Biostratigraphy of the Up 1974. Neogene Planktonic Foraminifera of the Indian per Tocuyo (San Lorenzo) and Pozon Formations, Ocean (DSDP, Leg 26). In Initial Reports of the Eastern Falcon, Venezuela. Bulletins of American Deep Sea Drilling Project, 26:675-741, plates 1- Paleontology, 39(178):59-252, plates 1-19. 14. Washington, D.C: National Science Founda 1969. Late Middle Eocene to Recent Planktonic Fora tion. miniferal Biostratigraphy. In P. Bronnimann and Boltovskoy, E., and S. Watanabe H.H. Renz, editors. Proceedings of the First Inter 1981. Foraminiferos de los sedimentos cuatarios entre national Conference on Planktonic Microfossils, Tierra del Fuego e Islas Georgias del Sur. Revista pages 199-422, plates 1-54. Leiden: EJ.Brill. Museo Argentino de Ciencias Naturales (Bernardino 1979. The Cainzoic Globigerinida. 3 volumes, 264 plates. Rivadavia) Geologia, 8(4):95-124, plates 1-5. 94 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Bradshaw, J. Foraminifera. Journal of Foraminiferal Research, 1959. Ecology of Living Planktonic Foraminifera in the 1(4):170-177. North Equatorial Pacific Ocean. Contributions 1974. Planktonic Foraminifera from the Mediterranean from the Cushman Foundation for Foraminiferal Re and Adjacent Atlantic Waters. Journal of Forami search, 10(2):25-64, figures 1-43. niferal Research. 4(4):171-183. Brady, H.B. 1976a. Evolution of Ocean Climate and the Record of 1882. Report on the Foraminifera. In Tizard and J. Planktonic Foraminifera. Nature, 264(5585):431- Murray, Exploration ofthe Faroe Channel During 432. the Summer of 1880, in Her Majesty's Hired Ship 1976b. Views and Observations on the Taxonomy of Cer "Knight Errant." Royal Society of Edinburgh Pro tain Neogene Planktonic Foraminiferal Species. ceedings, 11:708-717. In Y. Takayanagi and T. Saito, editors, Progress 1884. Report on the Foraminifera Collected by H.M.S. in Micropaleontology, pages 36-46, plates 1-3. C/ia//^n^^r during the Years 1873-1876. In Report New York: Micropaleontology Press, American on the Scientific Results ofthe Voyage ofthe Challenger Museum of Natural History. During the Years 1873-76, Zoology, 9:1-814, plates 1979. The Role of Circulation in the Parcelling and 1-115. Dispersal of North Atlantic Planktonic Foramini Brinton, E. fera. In]. Gray and A.J. Boucot, editors. Historical 1962. The Distribution of Pacific Euphasiids. Bulletin of Biogeography, Plate Tectonics and the Changing En the Scripps Institute of Oceanography, 8:(2):51-270. vironment, pages 417-425. Covallis: Oregon State Bronnimann, P., and N.K. Brown University Press. 1956. Taxonomy ofthe Globotruncanidae. Ecologae Geo 1982. Textural Observations on Some Living Species of logicae Helvetiae, 48(2):503-561, figures 1-24. Planktonic Foraminifera. Smithsonian Contribu Bronnimann, P., and J. Resig tions to Paleobiology, 45:1-45, plates 1-15. 1971. A Neogene Globigerinacean Biochronological Cifelli, R., and DJ. Belford Time-Scale of the Southwestern Pacific. In Initial 1977. The Types of Several Species of Tertiary Plank Reports of the Deep Sea Drilling Project, 7:1235- tonic Foraminifera in the Collections of the U.S. 1469, plates 1-51. Washington, D.C: National National Museum of Natural History. Journal of Science Foundation. Foraminiferal Research, 7(2):100-105, plates 1-2. Bush, G. Cifelli, R., and C.S. Benier 1975. Modes of Animal Speciation. Annual Reviews of 1976. Planktonic Foraminiferida from Near the West Ecology and Systematics, 6:339-364. African Coast and a Consideration of Faunal Par 1982. What Do We Really Know About Speciation? In celling in the North Atlantic. Journal of Forami R. Milkman, editor. Perspectives on Evolution, niferal Research, 6(4):258-273. pages 119-128. Sunderland, Massachusetts: Sin- Cifelli, R., and G. Glagon auer Associates. 1979. New Late Miocene and Pliocene Occurrences of Caron, M., and P. Homewood Globorotalia Species from the North Atlantic; and 1983. Evolution of Early Planktic Foraminifers. Marine a Paleogeographic rewev/. Journal of Foraminiferal Micropaleontology, 7(6):453-462. Research, 9{^):210-227. Carpenter, W.B., W.K. Parker, and T.R.Jones In press. Evolutionary Trends in E^rly-Middle Miocene 1862. Introduction to the Study of Foraminifera. 319 pages. Globorotalia of Trinidad. Proceedings ofthe Fourth London: Ray Society. Latin American Geological Congress. Catalano, R., and R. Sprovieri Cifelli, R., and C McCloy 1971. Biostratigrafia di Alcune Serie Saheliane (Messi- 1983. Planktonic Foraminifera and Euthecosomatus niano Inferiore) in Sicilia. In A. Farinacci, editor, Pteropods in the Surface Waters of the North Proceedings of the Second Planktonic Conference, Atlantic. Journal of Foraminiferal Research, pages 211-249, plates 1-5. Rome: Edizioni Tech- 13(2):91-107. noscienza. Cifelli, R., and R.K. Smith Cifelli, R. 1970. Distribution of Planktonic Foraminifera in the 1965. Planktonic Foraminifera from the Western North Vicinity of the North Atlantic Current. Smithson Atlantic. Smithsonian Miscellaneous Collections, ian Contributions to Paleobiology, 4:1-52, plates 1- 148(4): 1-35, plates 1-9. 6. 1969. Radiation of Cenozoic Planktonic Foraminifera. Cita, M.B. Systematic Zoology, 18(2): 154-168. 1973. Pliocene Biostratigraphy and Chronostratigraphy. 1971. On the Temperature Relationships of Planktonic In Initial Reports of the Deep Sea Drilling Project, NUMBER 58 95 13:1343-1379,plates 1-7. Washington, D.C: Na Eldredge, N., and SJ. Gould tional Science Foundation. 1972. Punctuated Equilibria: An Alternative to Phyletic Cita, M.B., M.L. Colalongo, S. D'Onofrio, S. laccarino, and Gradualism. In T.J.M. Schopf, editor. Models in G. Salvatorini Paleobiology, pages 82-115. San Francisco: Free 1978. Biostratigraphy of Miocene Deep-Sea Sediments man, Cooper and Company. (Sites 372 and 375), with Special Reference to the Endler, J.A. Messinian/pre-Messinian Interval. In Initial Re 1977. Geographic Variation, Speciation, and Clines. 246 ports of the Deep Sea Drilling Project, 42(1):67I- pages. Princeton: Princeton University Press. 707, plates 1-12. Washington, D.C: National Sci Ericson, D.B., M. Ewing, G. Wollin, and B.C. Heezen ence Foundation. 1961. Atlantic Deep-Sea Sediment Cores. Geological So Colalongo, M.L., and S. Sartoni ciety of American Bulletin, 72(2): 193-285, plates 1 - 1967. Globorotalia hirsuta aemiliana nuova sottospecie 3. cronologica del Pliocene in Italia. Giornale di Geo Fairbanks, R.G., M. Sverdlove, R. Free, P.H. Wiebe, and logia, 34(l):265-279, table 1. A.W.H. Be Cosijn, A.J. 1982. Vertical Distribution and Isotopic Fractionation 1938. Statistical Studies on the Phylogeny of Some Fo of Living Planktonic Foraminifera from the Pan raminifera. Cycloclypeus and Lepidocyclina from ama Basin. Nature, 298(5877):841-848. Spain, Globorotalia from the East Indies. Leidsche Feinberg, H., and H.G. Lorenz Geologische Mededeelingen, 10(1): 1-62. 1973. Le Ligne Evolutive de Globorotalia miozea s.l. dans Cracraft, J. le Miocene Mediterraneen. Notes et Memoires du 1974. Phylogenetic Models and Classification. Systematic Service Geologique du Maroc, 33:31-45, plates Zoo/ogy, 23(l):71-90. 1-3. 1982. A Non Equilibrium Theory for the Rate-Control Fleischer, R.L. of Speciation and Extinction and the Origin of 1974. Cenozoic Planktonic Foraminifera and Biostratig Macroevolutionary Patterns. Systematic Zoology, raphy, Arabian Sea Deep Sea Drilling Project, Leg 31(4):348-365. 23A. In Initial Reports of the Deep Sea Drilling D'Onofrio, S., L. Gianelli, S. laccarino, E. Morlotti, M. Project, 23:1001-1072, plates 1-21. Washington, Romeo, G. Salvatorini, M. Sampo, and R. Sprovieri D.C: National Science Foundation. 1976. Planktonic Foraminifera of the Upper Miocene Fortey, R.A., and R.P.S. Jefferies from Some Italian Sections and the Problem of 1982. Fossils and Phylogeny—A Compromise Ap the Lower Boundary of the Messinian. Bollettino proach. In K.A. Joysey and A.E. Friday, editors. della Societd Paleontologica Italiano, 14(2): 177- Problems of Phylogenetic Reconstruction, pages 197- 196, plates 1-5. 234. London: Academic Press. d'Orbigny, A.D. Gingerich, P.D. 1826. Tableau methodique de la classe des cephalo 1976. Cranial Anatomy and Evolution of Early Tertiary podes. Annales des Sciences Naturelles, series 1, Plesiadapidae (Mammalia, Primates). University of 7:95-315, plates 10-17. Michigan Papers on Paleontology, 15:1-140, plates Douglas, R.G., and S.M. Savin 1-12. 1978. Oxygen Isotopic Evidence for the Depth Stratifi Gingerich, P.D., and E.L. Simons cation of Tertiary and Cretaceous Planktic Fo 1977. Systematics, Phylogeny, and Evolution of Early raminifera. Marine Micropaleontology, 3(2): 175- Eocene Adapidae (Mammalia, Primates) in North 196. America. Contributions from the Museum of Paleon Dujardin, F. tology (University of Michigan), 24(22):245-279, 1835. Recherches sur les organismes inferieurs. Annales figures 1-13. Sciences Naturelle (Zoologie), 2(4):343-377. Glagon, G., C Vergnaud, L. Leclaire, and J. Sigal Fade, J. V. 1973. Presence des Foraminiferes: Globorotalia crassula 1973. Geographical Distribution of Living Planktonic Cushman and Stewart et Globorotalia hirsuta Foraminifera in the Southwest Pacific. In R. Fra- (d'Orbigny) en Mer Mediterranee. Revista Es zer, editor. Oceanography ofthe South Pacific, pages panola de Micropaleontologia, 5(3):373-401, plates 249-256. Wellington: New Zealand National 1-6. Commission for UNESCO. Gould, S.J. Eldredge, N., and J. Cracraft 1980. Is a New and General Theory of Evolution Emerg 1980. Phylogenetic Patterns and the Evolutionary Process: ing? Pa/^oiio/og)!, 6(1): 119-130. Methods and Theory in Comparative Biology. 349 1982. The Meaning of Punctuated Equilibrium and Its pages. New York: Columbia University Press. Role in Validating a Hierarchical Approach to 96 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Macroevolution. In R. Milkman, editor. Perspec gene Biostratigraphy, Osaka, 1981, pages 61-71. tives on Evolution, pages 83-104. Sunderland, Osaka: Osaka Museum of Natural History. Massachusetts: Sinauer Associates. 1982. Late Miocene to Pleistocene Globorotalia (Fo Gradstein, F. raminiferida) from DSDP Leg 29, Site 284, South 1974. Mediterranean Pliocene Globorotalia: A Biometrical west Pacific. New Zealand Journal of Geology and Approach, 128 pages, 13 tables. Meppel: published Geophysics, 25(l):83-99. by author [printed by Krips Repro.] Hoskins, R.H. Hart, M.B. 1984. The Taxonomy and Stratigraphic Record of Glo 1980. A Water Depth Model for the Evolution of the borotalia mayeri Cushman and Ellisor in New Zea Planktonic Foraminifera. Nature, 286(5770):252- land. Palaeogeography, Palaeoclimatology, Palaeoe 254. cology, 46{l/3):203-2l6. Healy-Williams, N. Hutchinson, G.E. 1983. Fourier Shape Analysis of Globorotalia truncatuli 1967. A Treatise on Limnology. 1115 pages. New York: noides from Late Quaternary Sediments in the Wiley. Southern Indian Ocean. Marine Micropaleontology, Jenkins, D.G. 8(1): 1-15, figures 1-8. 1965. Planktonic Foraminifera and Tertiary Interconti Healy-Williams, N., and D.F. Williams nental Correlations. Micropaleontology, 11(3):265- 1981. Fourier Analysis of Test Shape of Planktonic 277. Foraminifera. Nature, 289(5797):485-487, fig 1966a. Planktonic Foraminifera from the Type Aquitan- ures 1-3. ian-Burdigalian of France. Contributions from the Hecht, A.D., and S.M. Savin Cushman Foundation for Foraminiferal Research, 1970. Oxygen-18 Studies of Recent Planktonic Forami 17(1):1-15. nifera: Comparison of Phenotypes and of Test 1966b. Two Lineages from the Neogene Planktonic For Parts. 5a^n<:^, 170(3953):69-7l. aminifera of the Australasian Region. In Proceed 1972. Phenotypic Variation and Oxygen Isotope Ratios ings ofthe International Union of Geological Sciences in Recent Planktonic Foraminifera. Journal of Committee on Mediterranean Neogene Stratigraphy, Foraminiferal Research, 2(2):55-67. 3:23-29. Hemleben, C, A.W.H. Be, O.R. Anderson, and S. Tuntivate 1971. New Zealand Cenozoic Planktonic Foraminifera. 1977. Test Morphology, Organic Layers and Chamber New Zealand Geological Survey Paleontological Bul Formation of the Planktonic Foraminifer Globor letin, 42:1-275, plates 1-23, tables 1-58. otalia menardii (d'Orbigny). Journal of Foramini 1975. Cenozoic Planktonic Foraminiferal Biostratigra feral Research, 7(1): 1-25, plates 1-12. phy of the Southwestern Pacific and Tasman Hemleben, C, and M. Spindler Sea—DSDP Leg 29. In Initial Reports of the Deep 1983. Recent Advances in Research on Living Plank Sea Drilling Project, 29:449-467. Washington, tonic Foraminifera. Utrecht Micropaleontological D.C: National Science Foundation. Bulletins, 30:141-170, plates 1-4. 1977. Lower Miocene Planktonic Foraminifera from a Hornibrook, N. deB. Borehole in the English Channel. Micropaleontol 1961. Tertiary Foraminifera from Oamaru District ogy, 23(3):297-318, plates 1-5. (N.Z.). New Zealand Geological Survey Paleontolog 1978. Neogene Planktonic Foraminifers from DSDP ical Bulletin, 34:1-194, plates 1-28. Leg 40 Sites 360 and 362 in the Southeastern 1976. Globorotalia truncatulinoides and the Pliocene- Atlantic. In Initial Reports of the Deep Sea Drilling Pleistocene Boundary in Northern Hawkes Bay, Project, 40:723-739, plates 1-3. Washington, New Zealand. In Y. Takayanagi and T. Saito, D.C: National Science Foundation. editors, Progress in Micropaleontology, pages 83- Jenkins, D.G., and W.M. Orr 102, figures 1-6. New York: Micropaleontology 1972. Planktonic Foraminiferal Biostratigraphy of the Press, American Museum of Natural History. Eastern Equatorial Pacific—DSDP Leg 9. In Ini 1981a. Globorotalia (Planktic Foraminiferida) in the Late tial Reports ofthe Deep Sea Drilling Project, 9:1059- Pliocene and Early Pleistocene of New Zealand. 1193, plates 1-41. Washington, D.C: National New Zealand Journal of Geology and Geophysics, Science Foundation. 24(2):263-292, figures 1-11. Kaneps, A.G. 1981b. Evaluation of Pacific Southern Mid Latitude and 1975. Site 264: Biostratigraphic Summary. In Initial Re Equatorial Latitude Planktic Foraminiferal Datum ports of the Deep Sea Drilling Project, 28:23-25. Levels. In N. Ikebe, M. Chiji, R. Tsuchi, Y. Mo Washington, D.C: National Science Foundation. rozumi, and T. Kawata, editors. Proceedings of Keigwin, L.D. IGCP-I14 International Workshop on Pacific Neo 1982. Neogene Planktonic Foraminifers from Deep Sea NUMBER 58 97 Drilling Project Sites 502 and 503. In Initial Re Sea Drilling Project, 29:769-799. Washington, ports ofthe Deep Sea Drilling Project, 68:269-288, D.C: National Science Foundation. plates 1-11. Washington, D.C: National Science King, C Foundation. 1983. Cainozoic Micropaleontological Biostratigraphy Keller, G. of the North Sea. Institute of Geological Sciences 1978. Late Neogene Biostratigraphy and Paleoceanog- (United Kingdom) Report, 82(7): 1-40. raphy of DSDP Site 310, Central North Pacific Lamb, J.L., and J.H. Beard and Correlation with the Southwest Pacific. Ma 1972. Late Neogene Planktonic Foraminifers in the Car rine Micropaleontology, 3(2):97-119, plates 1-5. ibbean, Gulf of Mexico, and Italian Stratotypes. 1979a. Late Neogene Planktonic Foraminiferal Biostra University of Kansas Paleontological Contributions, tigraphy and Paleogeography of the Northwest 57:1-67, plates 1-36, table 1. Pacific DSDP Site 296. Palaeogeography, Palaeocli Lande, R. matology, Palaeoecology, 27(1/2): 129-154. 1980. Genetic Variation and Phenotypic Evolution dur 1979b. Late Neogene Paleoceanography of the North ing Allopatric Speciation. American Naturalist, Pacific DSDP Sites 173, 310, and 296. Marine 116(4):463-479. Micropaleontology, 4(2): 159-172. Lidz, B. 1981. The Genus Globorotalia in the Early Miocene of 1972. Globorotalia crassaformis Morphotype Variations the Equatorial and Northwestern Pacific, yourna/ in Atlantic and Caribbean Deep>-Sea Cores. Micro of Foraminiferal Research, 11(2): 118-132, figures paleontology, 18(2): 194-211. 1-3, plates 1-5. Lidz, B., A Kehm, and H. Miller 1983. Biochronology and Paleoclimatic Implications of 1968. Depth Habitats of Pelagic Foraminifera during Middle Eocene to Oligocene Planktic Foramini the Pleistocene. Nature, 2l7(5125):245-247. feral Faunas. Marine Micropaleontology, 7(6):463- Lipps, J.H. 486, figures 1-13. 1979. Ecology and Paleoecology of Planktic Foramini Keller, G., and J.A. Barron fera. In J.H. Lipps, W.H. Berger, M.A. Buzas, 1983. Paleoceanographic Implications of Miocene Deep- R.G. Douglas, and CA. Ross, Foraminiferal Ecol Sea Hiatuses. Geological Society of America Bulletin, ogy and Paleoecology, pages 62-104. Tulsa: Society 94(5):590-613. of Economic Paleontologists and Mineralogists. Kennett, J.P. [Society of Economic Paleontologists and Min 1966. The Globorotalia crassaformis Bioseries in North eralogists Short Course Notes No. 6, Houston, Westland and Marlborough, New Zealand. Micro Texas.] paleontology, 12(2):235-245, plates 1-2. 1981. What, If Anything, is Micropaleontology? Pa/eo- 1968. Globorotalia truncatulinoides as a Paleo-Oceano- biology,T{2):l67-l99. graphic Index. Science, 159(3822):1461-1463. Lohmann, G.P., and B.A. Malmgren 1976. Phenotypic Variation in Some Recent and Late 1983. Equatorward Migration of Globorotalia truncatu Cenozoic Planktonic Foraminifera. In R.H. Hed- linoides Ecophenotypes through the Late Pleisto ley and C.G. Adams, editors, Foraminifera, 2:111- cene: Gradual Evolution or Ocean Change? Paleo 170. London: Academic Press. biology, 9{4):4l4-42l. Kennett, J.P., and K.R. Geitzenauer Loutit, T.S., J.P. Kennett, and S.M. Savin 1969. Pliocene-Pleistocene Boundary in a South Pacific 1983. Miocene Equatorial and Southwest Pacific Paleo Deep-Sea Core. Nature, 224(5222):899-901. ceanography from Stable Isotope Evidence. Ma Kennett,J.P., N.J. Shackleton, S.V. Margolis, D.E. Goodney, rine Micropaleontology, 8(3):215-233. W.C. Dudley, and P.M. Kroopnick MacArthur, R.H., and E.O. Wilson 1979. Late Cenozoic Oxygen and Carbon Isotopic His 1967. The Theory of Island Biogeography, 203 pages. tory and Volcanic Ash Stratigraphy: DSDP Site Princton: Princton University Press. 284, South Pacific. American Journal of Science, Maiya, S., T. Saito, and T. Sato 279(l):52-69. 1976. Late Cenozoic Planktonic Foraminiferal Biostra Kennett, J.P., and M.S. Srinivasan tigraphy of Northwest Pacific Sedimentary Se 1983. Neogene Planktonic Foraminifera: A Phylogenetic At quences. In Y. Takayanagi and T. Saito, editors, las. 265 pages, 26 figures, 61 plates. Stroudsburg: Progress in Micropaleontology, pages 395-422, Hutchinson Ross. plates 1-6. New York: Micropaleontology Press, Kenneu,J.P.,and P. Vella American Museum of Natural History. 1975. Late Cenozoic Planktonic Foraminifera and Pa Malmgren, B.A., and J.P. Kennett leoceanography at DSDP Site 284 in the Cool 1981. Phyletic Gradualism in a Late Cenozoic Plank Subtropical Pacific. In Initial Reports of the Deep tonic Foraminiferal Lineage; DSDP Site 284, 98 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Southwest Pacific. Paleobiology, 7(2):230-240, fig 15:617-624, plates 1-2. Washington, D.C: Na ures 1, 2. tional Science Foundation. 1982. The Potential of Morphometrically Based Phylo- Parker, F.L. Zonation: Application of a Late Cenozoic Plank 1960. Living Planktonic Foraminifera from the Equa tonic Foraminiferal Lineage. Marine Micropaleon torial and Southeast Pacific. Science Reports of the tology, 7(4):285-296, plate 1. Tohoku University, Sendai, second series (Geology), Masters, B.A. special volume 4:71-82. 1977. Mesozoic Planktonic Foraminifera. In A.T.S. 1962. Planktonic Foraminiferal Species in Pacific Sedi Ramsay, editor. Oceanic Micropaleontology, 1:301- ments. Micropaleontology, 8(2):219-254, plates 1- 731, plates 1-58. London: Academic Press. 10. Mayr, E. 1967. Late Tertiary Biostratigraphy (Planktonic Fo 1963. Animal Species and Evolution. 797 pages. Cam raminifera) of Tropical Indo-Pacific Deep-Sea bridge: Belknap Press. Cores. Bulletins of American Paleontology, McGowan, J.A. 52(235): 115-208, plates 17-32. 1971. Oceanic Biogeography of the Pacific. In B.M. 1973. Late Cenozoic Biostratigraphy (Planktonic Fora Funnell, and W.R. Riedel, editors. The Micropa minifera) of Tropical Atlantic Deep-Sea Sections. leontology of Oceans, pages 3-74. Cambridge: Cam Revista Espanola de Micropaleontologia, 5(2):253- bridge University Press. 289. McGowran, B. Patterson, C 1968. Reclassification of Early Tertiary Globorotalia. Mi 1981. Significance of Fossils in Determining Evolution cropaleontology, 14(2): 179-198, plates 1-4. ary Relationships. Annual Reviews in Ecology and Systematics, 12:195-223. Molina, E. Paul, CR.C 1979. Oligoceno-Mioceno Inferior por Medio de Fora 1982. The Adequacy ofthe Fossil Record. In K.A. Joy miniferos Planctonicos en el Sector Central de las sey, and A.E. Friday, editors. Problems of Phyloge Cordilleras Beticas (Espafia). 342 pages, 37 plates. netic Reconstruction, pages 75-112. London: Aca Doctoral dissertation. University of Granada, demic Press. Spain. Perconig, E., C Martinez, and L. Granados Moore, T.C, T.H. van Andel, C Sancetta, and N. Pisias 1980. Globorotalia andalusiana, nueva especie de Fora- 1978. Cenozoic Hiatuses in Pelagic Sediments. Micropa minifero del Mioceno terminal (Andaluciense). leontology, 24(2): 113-138. Revista Espanola de Micropaleontologia, 12(1):27- Nelson, C, and D.A. Burns 39, plates 1-3. 1982. Effect of Sampling Interval on the Resolution of Pessagno, E. Oxygen Isotopic Paleotemperature Trends—An 1967. Upper Cretaceous Planktonic Foraminifera from Example from the New Zealand Early Miocene. the Western Gulf Coastal Plain. Paleontographica New Zealand Journal of Geology and Geophysics, Americana, 5(37):246-446, plates 48-101. 25(1):77-81. Petters, S.W., H.A. El Nakhal, and R. Cifelli Oba, T. 1983. Costellagerina, a New Late Cretaceous Globigerine 1969. Biostratigraphy and Isotopic Paleotemperatures Foraminiferal Genus, yowrna/ of Foraminiferal Re of Some Deep-Sea Cores from the Indian Ocean. search, 13(4):247-251, plate 1. Science Reports of the Tohoku University, Sendai, Phillips, J.D., W.A. Berggren, A. Bertels, and D. Wall second series (Geology), 41(2): 129-195. 1968. Paleomagnetic Stratigraphy and Micropaleontol Oda, M. ogy of Three Deep-Sea Cores from the Central 1977. Planktonic Foraminiferal Biostratigraphy of the North Atlantic Ocean. Earth and Planetary Science Late Cenozoic Sedimentary Sequence, Central Letters, 4:118-130. Honshu, Japan. Science Reports of the Tohoku Uni Phleger, F.B. versity, Sendai, second series (Geology), 48(1):1- 1951. Ecology of Foraminifera, Northwest Gulf of Mex 72, plates 1-10. ico, Part 1: Foraminiferal Distributions. Geological Olsson, R.K. Society of America Memoir, 46:1-88. 1972. Growth Changes in the Globorotalia fohsi Lineage. Pierrot-Bults, A.C, and S. van der Spoel Ecologae Geologica Helvetiae, 65(1): 165-184, fig 1979. Speciation in Macrozooplankton. In S. van der ures 1-13. Spoel and A.C. Pierrot-Bults, editors. Zoogeogra 1973. Growth Studies on Globorotalia exilis Blow and phy and Diversity in Plankton, pages 144-167. Globorotalia pertenuis Beard in the Hole 154A Utrecht: Bunge Scientific Publishers. Section, Leg 15, Deep Sea Drilling Project. In Poignant, A., and C Pujol Initial Reports of the Deep Sea Drilling Project, 1976. Nouvelles donnees micro-paleontologiques (fora- NUMBER 58 99 miniferes planktoniques et petits foraminiferes Saito, T. benthiques) sur le stratotype de I'Aquitanien. Geo 1977. Late Cenozoic Planktonic Foraminiferal Datum bios 9(5):607-663, plates 1-16. Levels: The Present State of Knowledge Toward Poore, R.Z. Accomplishing Pan-Pacific Stratigraphic Correla 1979. Oligocene through Quaternary Planktonic Fora tion. In T. Saito, and H. Ujiie, editors. Proceedings miniferal Biostratigraphy of the North Atlantic: ofthe First International Congress on Pacific Neogene DSDP Leg 49. In Initial Reports of the Deep Sea Stratigraphy, Tokyo, 1976, pages 61-80. Tokyo: Drilling Project, 49:447-517, figures 1-7, plates Science Council of Japan. 1-20, tables 1-7. Washington, D.C: National Sci Saito, T., P.R. Thompson, and D. Breger ence Foundation. 1981. Systematic Index of Recent and Pleistocene Planktonic 1981. Late Miocene Biogeography and Paleoclimatol Foraminifera. 190 pages, 56 plates. Tokyo: Uni ogy of the Central North Atlantic. Marine Micro versity of Tokyo Press. paleontology, 6(5/6):599-616. Savin, S.M., R.G. Douglas, and F.G. Stehli Poore, R.Z., and W.A. Berggren 1975. Tertiary Marine Paleotemperatures. Geological So 1974. Pliocene Biostratigraphy ofthe Labrador Sea: Cal ciety of American Bulletin 86(11): 1499-1510, fig careous Plankton. Journal of Foraminiferal Re ures 1-14. search, 4(3):91-108, plates 1-3. Schindel, D.E. 1975. Late Cenozoic Planktonic Foraminiferal Biostra 1982. Resolution Analysis: A New Approach to the Gaps tigraphy and Paleoclimatology of Hatton-Rockall in the Fossil Record. Paleobiology, 8(4):340-353. Basin: DSDP Site \ 16. Journal of Foraminiferal Schmidt, K. Research, 5(4):270-293, plates 1-5. 1934. Biometrische Untersuchungen an Foraminiferan Postuma, J.A. aus dem Pliozaen von Ceram. Ecologae Geologicae 1971. Manual of Planktonic Foraminifera. 420 pages. Am Helvetiae, 27(1):46-134. sterdam; Elsevier Publishing Company. ScoU, G.H. Pujol, C 1972. The Relationship between the Miocene Forami 1983. Cenozoic Planktonic Foraminiferal Biostratigra niferida Globorotalia miozea miozea and G. praemen phy of the Southwestern Atlantic (Rio Grande ardii. Micropaleontology, 18(l):81-93, plates 1-2. Rise): Deep Sea Drilling Project Leg 72. In Initial 1973a. Peripheral Structures in Chambers oi Globorotalia Reports of the Deep Sea Drilling Project, 72:623- scitula praescitula and Some Descendants. Revista 673, plates 1-19, tables 1-8. Washington, D.C: Espanola de Micropaleontologia, 5(2):235-246, National Science Foundation. plates 1-2. Quilty, P.G. 1973b. Ontogeny and Shape in Globorotalia menardii. 1976. Planktonic Foraminifera DSDP Leg 34-Nazca Journal of Foraminiferal Research, 3(3):142-164. Plate. In Initial Reports of the Deep Sea Drilling 1975. Variation in Globorotalia miozea (Foraminiferida) Project, 34:629-703, plates 1-19. Washington, from the New Zealand Neogene. New Zealand D.C: National Science Foundation. Journal of Geology and Geophysics, 18(6):865-880. Rogl, F. 1976. Globorotalia crassula (Foraminiferida): Blow's In 1974. The Evolution ofthe Globorotalia truncatulinoides terpretation Considered Biometrically. Palaeontol and Globorotalia crassaformis Group in the Pli ogy, 19(1):95-105, plate 16. ocene and Pleistocene of the Timor Trough, 1980a. Globorotalia infiata Lineage and G. crassaformis DSDP Leg 27, Site 262. In Initial Reports of the from Blind River, New Zealand: Recognition, Re Deep Sea Drilling Project, 27:743-767, plates 1-5. lationship, and Use in Uppermost Miocene— Washington, D.C: National Science Foundation. Lower Pliocene Biostratigraphy. New Zealand Ryan, W.F.B., M.B. Cita, M.D. Rawson, L.H. Burckle, and Journal of Geology and Geophysics, 23(5/6):665- T. Saito 677. 1974. A Paleomagnetic Assignment of Neogene Stage 1980b. Upper Miocene Biostratigraphy: Does Globorotalia Boundaries and the Development of Isochronous conomiozea occur in the Messinian? Revista Espan Datum Planes between the Mediterranean, the ola de Micropaleontologia, 12(3):489-506, plates Pacific and Indian Oceans in Order to Investigate 1-3. the Response of the World Ocean to the Mediter 1982. Tempo and Stratigraphic Record of Speciation in ranean "Salinity Crisis." Rivista Italiana di Paleon Globorotalia puncticulata. Journal of Foraminiferal tologia e Stratigrafia, 80(4):631-687, tables 1-7. Research, 12(1): 1-12, figures 1-11. Sadler, P.M. 1983. Biostratigraphy and Histories of Upper Miocene- 1981. Sediment Accumulation Rates and the Complete Pliocene Globorotalia, South Atlantic and South ness of Stratigraphic Sections. Journal of Geology, west Pacific. Marine Micropaleontology, 7(5):369- 89(5):569-584. 383, plates 1-2. 100 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Shackleton, NJ., and J.P. Kennett Characteristics of Index Forms. University of Kan 1975. Paleotemperature History of the Cenozoic and sas Paleontological Contributions, 62:1-425, figures the Initiation of Antarctic Glaciations: Oxygen 1-213. and Carbon Isotope Analyses in DSDP Sites 277, Stanley, S.M. 279, and 281. In Initial Reports ofthe Deep Sea 1979. Macroevolution: Pattern and Process. 332 pages. Drilling Project, 29:743-755, figures 1-8. Wash San Francisco: Freeman, Cooper and Company. ington, D.C: National Science Foundation. Steineck, P.L., and R.L. Fleischer Shafik, S., and G.C.H. Chaproniere 1978. Towards the Classical Reclassification of Cenozoic 1978. Nannofossil and Planktic Foraminiferal Biostratig Globigerinacea (Foraminiferida). Journal of Pa raphy Around the Oligocene-Miocene Boundary leontology, 52(3):618-632, plates 1-2. in Parts ofthe Indo-Pacific Region. BMR Journal Stommel, H. of Australian Geology and Geophysics, 3:135-151. 1965. The Gulf Stream. 248 pages. Berkeley: University Shannon, L.V., G.H. Stander, and J.A. Campbell of California Press. 1973. Oceanic Circulation Deduced from Plastic Drift Takayanagi, Y., N. Niitsuma, and T. Sakai Cards. Sea Fisheries Branch, Department of Indus 1968. Wall Microstructure of Globorotalia truncatuli tries Republic of South Africa Investigational Report, noides (d'Orbigny). Science Reports of the Tohoku 108:1-31. University, second series (Geology), 40(2): 141- Smayda, T.J. 170, figures 1-4, plates 20-31. 1970. The Suspension and Sinking of Phytoplankton in Takayanagi, Y., and T. Saito the Sea. Oceanography and Marine Biology, 8:353- 1962. Planktonic Foraminifera from the Nobori For 414. mation, Shikoku, Japan. Science Reports ofthe To Smith, CC, and E.A. Pessagno hoku University, second series (Geology) special 1973. Planktonic Foraminifera and Stratigraphy of the volume, 5:67-105, plates 24-28. Corsicana Formation (Maestrichtian) North Cen Takayanagi, Y., T. Takayama. T. Sakai, and M. Oda tral Texas. Cushman Foundation for Foraminiferal 1976. Microbiostratigraphy of some Middle Miocene Se Research Special Publication, 12:1-68, plates 1-27. quences in Northern Japan. In Y. Takayanagi, Spaak, P. and T. Saito, editors. Progress in Micropaleontology, 1981. The Distribution of the Globorotalia infiata Group pages 356-381, plates 1-4. New York: Micropa in the Mediterranean Pliocene. Proceedings of the leontology Press, American Museum of Natural Koninklijke Nederlandse Akademie van Wetenschap History. pen, B84(2):201-215, plates 1-2. Templeton, A.R. 1983. Accuracy in Correlation and Ecological Aspects 1980. Modes of Speciation and Inferences Based on of the Planktonic Foraminiferal Zonation of the Genetic Distances. Evolution, 34(4):719-729. Mediterranean Pliocene. Utrecht Micropaleontolog 1982. Adaptation and the Integration of Evolutionary ical Bulletins, 28:1-159, plates 1-10. Forces. In R. Milkman, editor, Perspectives on Ev Srinivasan, M.S., and J.P. Kennett olution, pages 15-31. Sunderland, Massachusetts: 1981a. A Review of Neogene Planktonic Foraminiferal Sinauer Associates. Biostratigraphy: Applications in the Equatorial Theyer, F. and South Pacific. Society of Economic Paleontolo 1973. Globorotalia infiata triangula, a New Planktonic gists and Mineralogists Special Publication, 32:395- Foraminiferal Subspecies, yourna/ of Foraminferal 432, figures 1-14. Research, 3(4): 199-201, plate 1. 1981b. Neogene Planktonic Foraminiferal Biostratigra Thompson, P.R. phy and Evolution: Equatorial to Subantarctic, 1982. Foraminifers ofthe Middle America Trench. In South Pacific. Marine Micropaleontology, 6(5/ Initial Reports of the Deep Sea Drilling Project, 6):499-533, figures 1-14, plate 1. 67:351-381. Washington, D.C: National Science Stainforth, R.M.,J.L. Lamb, and R.M.Jeffords Foundation. 1978. Rotalia menardii Parker, Jones and Brady 1865 Tjalsma, R.C. (Foraminiferida): Proposed Suppression of Lec 1971. Stratigraphy and Foraminifera of the Neogene of totype and Designation of Neotype Z.N.(S.)2145. the Eastern Guadalquivir Basin (Southern Spain). Bulletin of Zoological Nomenclature, 34(4):252- Utrecht Micropaleontological Bulletins, 4:1-161, fig 262, plates 1-2. ures 1-28, plates 1-16. Stainforth, R.M., J.L. Lamb, H. Luterbacher, J.H. Beard, 1977. Cenozoic Foraminifera from the South Atlantic, and R.M. Jeffords DSDP Leg 36. In Initial Reports of the Deep Sea 1975. Cenozoic Planktonic Foraminiferal Zonation and Drilling Project, 36:493-517, plates 1-7. Washing- NUMBER 58 101 ton, D.C: National Science Foundation. 8(1):109-127, figures 1-8. Tolderlund, D.S., and A.W.H. Be Wernii, R. 1971. Seasonal Distribution of Planktonic Foraminifera 1977. Les Foraminiferes Planktoniques de la limite Mio- in the Western North Atlantic. Micropaleontology, Pliocene dans les environs de Rabat (Maroc). Eco 17(3):297-329, Stables. logae Geologicae Helvetiae, 70(1): 143-191, plates Ujiie, H., and S. Hariu 1-7. 1975. Early Pliocene to Late Middle Miocene Planktonic 1980. Le Messinien a Globorotalia conomiozea (Forami- Foraminifera from the Type Section ofthe Sagara nifere Planctonique) de la cote Mediterraneenne Group, Central Japan. Bulletin ofthe National Sci Marocaine. Ecologae Geologicae Helvetiae, 73(1): ence Museum {Tokyo), series C (Geology), I(2):37- 71-93, plates 1-4. 54, plates 1-3. Williamson, P.G. Van Valen, L. 1981. Palaeontological Documentation of Speciation in 1965. Review of "Evolutionary Trends in Foraminifera." Cenozoic Molluscs from Turkana Basin. Nature, Quarterly Review of Biology, 40(2): 188-189. 293(5832):437-443. Vincent, E. Wright, S. 1977. Indian Ocean Neogene Planktonic Foraminiferal 1932. The Roles of Mutation, Inbreeding, Crossbreed Biostratigraphy and its Paleoceanographic Impli ing and Selection in Evolution. In Proceedings of cations, /n J.R. Heirtzler, H.M. Bolli, T.A. Davies, the Sixth International Congress of Genetics (Ithaca J.B. Saunders, and J.G. Sclater, editors, Indian New York), 1:356-366, figures 1-8. New York: Ocean Geology and Biostratigraphy, pages 469-584. Brooklyn Botanic Gardens. Washington, D.C: American Geophysical Union. 1982. Character Change, Speciation, and the Higher 1981. Neogene Planktonic Foraminifers from the Cen Taxa. Evolution, 36(3):427-443. tral North Pacific, Deep Sea Drilling Project Leg Zachariasse, W.J. 62. In Initial Reports ofthe Deep Sea Drilling Project, 1975. Planktonic Foraminiferal Biostratigraphy of the 62:329-353. Washington, D.C: National Science Late Neogene of Crete (Greece). Utrecht Micropa Foundation. leontological Bulletins, 11:1-170, plates 1-17. Vincent, E., W.E. Frerichs, and M.E. Heiman Zachariasse, W.J., and P. Spaak 1974. Neogene Planktonic Foraminifera from the Gulf 1983. Middle Miocene to Pliocene Paleoenvironmental of Aden and the Western Tropical Indian Ocean, Reconstruction of the Mediterranean and Adja Deep Sea Drilling Project, Leg 24. In Initial Re cent Atlantic Ocean: Planktonic Foraminiferal ports ofthe Deep Sea Drilling Project, 24:827-849, Record of Southern Italy. Utrecht Micropaleonto plates 1-2. Washington, D.C: National Science logical Bulletins, 30:91-110. Foundation. Zeitzschel, B. Walters, R. 1978. Oceanographic Factors Influencing the Distribu 1965. The Globorotalia zealandica and G. miozea lineages. tion of Plankton in Space and Time. 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