Cushman Foundation Special Publication No. 46 p. 481-494, 2018 Chapter 18 TAXONOMY, BIOSTRATIGRAPHY, AND PHYLOGENY OF OLIGOCENE CASSIGERINELLA Paul N. Pearson1, Silvia Spezzaferri2, Brian T. Huber3, and Michal Kučera4 1School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, U.K. Email: [email protected] 2Department of Geosciences, University of Fribourg, Ch du Musée 6, 1700 Fribourg, Switzerland. Email: [email protected] 3Department of Paleobiology, MRC 121, Smithsonian Museum of Natural History, Washington, D.C. 20013-7012, U.S.A. Email: [email protected] 4MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. Email: [email protected] ABSTRACT The taxonomy, biostratigraphy, and phylogeny of test microstructure, with minute-scale internal Oligocene Cassigerinella is reviewed. Cassigerinella ornamentation (‘endospikes’). Only two species is in Superfamily Guembelitrioidea and Family occur in the Oligocene and are recognized as valid Cassigerinellidae. It is distinguished by its ‘twisted in this work: Cassigerinella chipolensis (Cushman enrolled-biserial’ coiling mode and distinctive and Ponton) and Cassigerinella eocaenica Cordey. INTRODUCTION common species, Cassigerinella chipolensis, was a surface dwelling form (Boersma and Shackleton, 1978; Cassigerinella is a distinctive genus with an Pearson and Wade, 2009) and it is likely that the other unusual coiling mode and wall texture. It is frequently members of the genus had a similar habitat. encountered in sediments of late Eocene to middle There has been some debate in the literature on Miocene age, within which interval subtle changes the style of chamber addition through ontogeny, which in size and shape are of considerable potential in on first inspection can appear haphazard. Pokorný regional biostratigraphic correlation (Premoli Silva and (1955:138) noted that later-formed chambers ‘alternate’, Spezzaferri, 1990; Spezzaferri, 1994). Its planktonic that is the chambers have reflective symmetry and habit is indicated by its distribution in open ocean successive apertures / foramina face each other rather marine sediments (Hughes and Jenkins, 1981) and than all facing the same way (hence apertures do not general test morphology, including the rather globular define an anterior direction and there is no dorsal or chambers (Li, 1986; Huber and others, 2006). Its ventral side). Pokorný suggested that the earliest whorl occurrence can be quite patchy both stratigraphically could be planispiral or trochospiral although it was and geographically (e.g., Jenkins, 1971) and it is likely difficult for him to be sure. Saito and Biscaye (1977) that it was an opportunistic genus, blooming in the described this distinctive coiling type as ‘enrolled- surface mixed-layer when trophic conditions were biserial’, indicating that the test was fundamentally suitable. Stable isotope evidence indicates that the most biserial but coiled back on itself. Li (1986:52, his fig. Pearson, Spezzaferri, Huber, and Kučera 1) elaborated on this by pointing out that the plane channels (Pearson and Wade, 2009). A distinctive of enrollment itself twists through ontogeny, most feature is the presence of small micron-sized spikes markedly in forms with inflated globular chambers scattered on the interior surface, called ‘endospikes’ (e.g., typical Cassigerinella chipolensis). Presumably by Pearson and Wade (2009). This is apparently a this additional twisting allows successive apertures to unique feature in foraminifera. The presence of these be positioned clear of the earlier chambers and for the endospikes on the chamber interiors implies an unusual test to maintain a globular shape overall. We agree with calcification mechanism. D’ Haenens and others (2012) Li (1986) that this ‘twisted enrolled-biserial’ coiling observed similar endospikes in a dissected specimen seems to be the pattern of chamber addition from the of Chiloguembelina wilcoxensis. That observation earliest ontogenetic stages onward and we have not helps cement a link between Chiloguembelina and observed an initially planispiral or trochospiral phase Cassigerinella. Presumably the latter evolved by in any of the specimens examined, despite the earlier developing a secondarily enrolled coiling mode, which suggestions of various authors including Pokorný maintains the fundamental biserial arrangement. Other (1955), Cordey (1968), and Blow (1979:1362). species of Chiloguembelina do not show endospikes Hofker (1963) made detailed studies of the (see Chapter 15, this volume), so presumably the apertural system in Cassigerinella and, working near ancestor was C. wilcoxensis itself, although a large the limit of resolution of the light microscope, claimed stratigraphic gap exists between the highest known to observe an internal “toothplate”; that is, a flange occurrence of that species and the lowest Cassigerinella extending inward from the aperture and either joining (Huber and others, 2006). Stratigraphic ranges and with, or approaching the foramen of the preceding inferred phylogenetic relationships are illustrated in chamber (See Hofker, 1963, pl. 1, figs. 2b, 2e, 2g, and Figure 18.1. 3a). Steineck and Darrell (1971) also recorded this The systematic taxonomy of Oligocene feature in C. chipolensis. If so, this observation would Cassigerinella is described in the following section. provide good evidence of a phylogenetic linkage with We note for completeness that an alleged species the benthic genus Cassidulina which has this character of Cassigerinella from the Oligocene of Cuba as well as enrolled-biserial coiling (Banner, 1982; for (Cassigerinella regularis Iturralde-Vinent, 1966) is not discussion of the toothplate in benthic cassidulinids see referable to the genus and is very probably a benthic Nomura, 1983, and Li, 1986). However, SEM studies species (Li, 1986). by Fleisher (1974), Saito and Biscaye (1977), Blow (1979), Li (1986), Spezzaferri (1994), and Pearson SYSTEMATIC TAXONOMY and Wade (2009) among others have failed to reveal any evidence of toothplates. Instead, apertures and Superfamily GUEMBELITRIOIDEA, foramina commonly possess an irregular lip with a Montanaro Gallitelli, 1957 ragged outward-directed flange (see, for example, Plate 18.1, Figs. 4-6, 8, and 12). DISCUSSION.— The discovery by D’Haenens and The external wall texture is essentially smooth others (2012) of endospikes in Chiloguembelina, but may be pustulose to various degrees or bearing pore virtually identical to those described in Cassigerinella mounds. In general, the more pustulose forms tend to be by Pearson and Wade (2009), is good evidence that from the Oligocene, whereas Miocene forms are usually the two genera belong to the same phylogenetic group, smoother. There is, however, substantial variability and that the wall texture of Cassigerinella is a subtype even on individual tests and we do not use the degree of the ototara-type wall. The ototara-type wall helps of smoothness to separate taxa (see discussion under define a distinct higher taxonomic group. For that Cassigerinella chipolensis, below). The wall texture in reason we assign the Cassigerinellidae to Superfamily cross-section was described in detail by Pearson and Guembelitrioidea. Wade (2009), and is named the chipolensis-subtype wall (see Chapter 15, this volume). Although some Family CASSIGERINELLIDAE Bolli, Loeblich, earlier workers (e.g., Hofker, 1963) thought the wall had and Tappan, 1957, revised Li, 1986 a radial texture, it is in fact microgranular (as originally observed by Blow, 1979:1361) with expanding pore Type genus: Cassigerinella Pokorný, 1955. 482 Chapter 18 - Cassigerinella (2009:198) described the distinctive wall texture of suppressed the Cassigerinellidae. Pearson and Wade a close relationship with moved Planktonic Foraminifera to include just the type genus. In the Family the restricted (1986) Li another. one to unrelated several genera that are now regarded as essentially Cassigerinellidae, Bolli and others (1957) included DISCUSSION Srinivasan, 1983; WPBP, 2011 = Wade and others (2011). = Berggren and others, 1995; K&S, 1983 = Kennett and ic relationships of Oligocene FIGURE 34 33 35 32 31 30 29 28 27 26 25 24 23 22 GPTS Age (Ma) Cassigerinella Cande & Kent (1995) 18.1. Stratigraphic ranges and inferred phylogenet EOCENE OLIGOCENE MIOCENE Epoch . LATE EARLY LATE EARLY — In their original concept of Family P22 P16 P18 P19 P20 P17 P21 N4 Former P Zones (Sub) a b (BKSA, 1995) & tropical a b N Zones (K&S, 1983) E15 E16 O1 O2 O3 O4 O5 O6 O7 to the Globigerinitidae, implying Globigerinitidae, the to M1 E, O and M Zones (Sub) (WPBP, 2011) tropical , Huber and others (2006:449) others and Huber , a b AE10 Tenuitella AE9 AO1 AO2 AO3 AO4 Huber & Quillévéré Antarctic Cassigerinella (2005) chipolensis C a eocaenica s s , and in so doing i g Atlas ofEocene e r i n e . BKSA, 1995 l l eocaenica a chipolensis - Radford, 1992;Huberandothers,2006:470). a different coiling pattern and wall texture (Li and the middle Eocene genus and (2012:166), BouDagher-Fadel it does not include under discussion also including the Miocene genus Family is regarded as either monogeneric or possibly Chiloguembelina been observed in as the named the distinctive wall texture of this Family we follow here. Pearson (Chapter 15, this volume) they resurrected Family Cassigerinellidae, which Accordingly Globigerinitidae. the in seen wall different Cassigerinella Cassidulina chipolensis Cassigerinella globulosa ? Radford, 1991;Huberandothers,2006).