CONTRIBUTIONS FROM THE CUSHMAN FOUNDATION FOR FORAMINIFERAL RESEARCH VOLUME XIX, Part 4 October, 1968 Contents No. 352. Acceleration of the Evolutionary Rate in the Orbulina Lineage I D. Graham Jenkins ....................................................................................................................................................... _. ___ 133 'No. 353. A New Genus of the Haplophragmoidinae from Malaysia D. S. Dhillon ,- 140 No. 354. Late Eocene and Early Oligocene Planktonic Foraminifera from Port Eliz­ , abeth and Cape Foulwind, New Zealand M. S. Srinivasan .:, ........ _.... _....... __ 142 No. 355. The Genus Sigmoilopsis Finlay 1947 from Cardigan Bay, Wales. Keith Atkinson ..................... .. ...................... .......... ........ ................................................................................ _...... ___ 160 No. 356. Preliminary Report on Some Littoral Foraminifera from Tomales Bay, California Don Maurer ............... ...... ................ ................................................................... _.. ___ 163 No. 357. A Taxonomic Note on Massilina carinata (Fornasini, 1905) Keith Atkinson 165 No. 358. A New Species of Pseudoguembelina from the Upper Cretaceous ~ Texas G. C. Esker, ill .............................................................................................................................................. __ 168 No. 359. Designation of a Lectotype of Globotruncana rosetta (Carsey) G. C. Esker, ill ......................... ............................................. ......................................................................................._ ... _. 170 Recent Literature on the Foraminifera Ruth Todd .... ................................................................................. .. 172 Index to Volume XIX, 1968 .................................................................................... .............................................................. _ \83 1968 CONTRIBUTIONS FROM THE CUSHMAN FOU NDATION FOR FORftMINIFERAL RESEARCH In CONTRIBUTIONS FROM THE CUSHMAN FOUNDA lION FOR FORAMINIFERAL RESEARCH VOLUME XIX, PART 4, OCTOBER, 1968 352. ACCELERATION OF THE EVOLUTIONARY RATE IN THE ORBULINA LINEAGE D. GRAHAM J ENKINS Geology Department, University of Canterbury, Christchurch, New Zealand ABSTRACT a concommittant increase in the number of aper­ The stratigraphic ranges of 9 taxa of the Orbulina evo· tures correlated with a decrease in the apertural size. lulionary lineage from 4 Australasian Mi ocene sequences have been plotted against sediment thicknesses and Indl· The first recognized taxon in the Orbulina lin­ c~\te an evolutionary a cceleration from Globhterillohles eage is Globigerina woodi woodi Jenkins (text fig. trllobus bhUlhericus Todd through to Orbulina. unlversa 2) which has 3-4 chambers in the final whorl and d'Orblgny. A correlation w ith radiometric data indicates that the first 3 taxa of the lineage appeared within about a single umbilical aperture, and the end form is 6 m.y. a nd the last 6 taxa appeared within only 2 m .Y. Orbulina universa d'Orbigny (text fig. 2) which has The possible biological s ignificance of the results and tax~ a spherical test with a large number of small aper­ onomle rates are discussed. tures scattered over the test surface. All the inter­ mediate morphologies exist within the lineage, but INTRODUCTION only 7 other named taxa are here recognized. Rep­ The Orbulina evolutionary lineage has been re­ resentatives of the 9 taxa have been illustrated from corded by many workers in Miocene sequences the Miocene Muddy Creek section, New Zealand from many parts of the world (see Jenkins, 1965). (text fig. 2). Stratigraphically the lineage can be traced through The taxa within the continually evolving Orbul­ from the Lower Miocene Globigerina woodi Jenkins ina lineage have been arbitrarily defined, and from to the end form Orbulina universa d'Orbigny in the the writer's experience some are more easily identi­ Middle Miocene which ranges through to the pres­ fi able than others. Taxonomically, the difficulties ent. This paper is an attempt to compare the meas­ of accurate identification and delineation of the urement of the phylogenetic rate of evolution with­ taxa lie in the region between ancestor and immedi­ in the O. universa lineage. ate descendant and the problems are especially From a comparison of the stratigraphic initial true of the following taxa in table 1. appearance of 9 named taxa within the Orbulina lineage in 4 stratigraphic sections from New Zea­ IMMEDIATE ANCESTOR DESCENDANT land and Australia (text fig. 1), it is suggested that there was an increase in the evolutionary tempo in Praeorbulina glomerosa Praeorbulina glomerosa the upper part of the lineage towards the Middle glomerosa (Blow) circularis (Blow) Miocene. There is slight evidence that there was a Praeorbulina glomerosa Praeorbulina glomerosa decrease in the tempo after the appearance of Orb­ cur va (Blow) glomerosa (Blow) ulina sUlllralis Bronnimann. Globigerinoides trilobus Praeorbulina glomerosa bisphericus (Todd) curva (Blow) ACKNOWLEDGEMENTS Globigerilloides tri/obus Globigerinoides trilobus The writer is indebted to many people, including trilobus (Reuss) bisphericus Todd Professor Alan Wood who provided the academic Globigerina woodi Globigerilla woodi climate at Aberystwyth, Wales during 1956-59 woodi Jenkins connecta Jenkins when this paper was first formulated as part of a Ph.D. thesis, and Dr. W. A. Berggren for providing TABLE 1 the quoted unpublished and radiometric data. Dur­ Pairs of ancestors and immediate descendants ing the ensuing period I have gained from innumer­ which are difficult to differentiate where the strati­ able discussions with many paleontologists. The graphic ranges and morphologies overlap. writer is further indebted to both Mr. R. C. Brazier The separating lines between the above ancestors of the New Zealand Geological Survey who made and descendants have been fixed arbitrarily by vari­ the illustrations of the specimens and to Miss L. ous micropaleontologists, and one method of pro­ Fiddes of the Geology Department, University of ducing consistently accurate identifications is by Canterbury, who assembled the figures. relating each taxonomic identification to each holo­ ORBULINA EVOLUTIONARY LINEAGE type, which is -regarded as the central morphologi­ The chief morphological changes within the Orb­ cal type. The writer has discussed the differences ulina lineage are the progressive envelopment of between Globigerilla woodi woodi and Globigerilla the earlier part of the test by the final chamber and woodi COllllecta (Jenkins, 1964), and Blow (1956) 134 JENKINS-EVOL U TION IN ORBULINA LINEAGE r-------------r-----------~r-----------_,------------~IO·S AUSTRALIA ~----------~~~--------------~----------------4_--------------~20· 30· ~--------------~--------------~--------------~~~~~~--~40· NEW ZEALAND L---------------L-______________L- ______________L- ____________~50· 150· 160· 170· 180· TEXT FIGURE 1 Location map discussed the differences between the other taxa A similar clear distinction occurs between Or­ recorded in table 1. bulina su/uralis and Praeorbulina g/omerosa circu­ The morphological differences between the other laris where the latter has small sutural openings taxa within the lineage are more definite. Thus the limited to the outline of the Globigerina stage, and ancestor Globigerina woodi cOli/recta differs from the former has the minute apertural openings also its immediate descendant Globigerinoides /ri/obus outside the sutures (text fig. 2). /ri/obus by having a single umbilical aperture as The taxonomic distinction between the two Or­ opposed to the umbilical aperture plus an additional bulilla species is distinct if 0. ulliversa is defined as aperture or apertures on the spiral side of G. /ri­ having a scatter of small apertures all over the sur­ lobus tri/obus (text fig. 2). face of the test (text fig. 2). CONTRIB L' TJONS FROM T H E CUSHMAN FOL'NDATION FOR FORA1\IrNIF I ~RAL R E S E ARCH 135 ORBULINA LINEAGE LAKES NEW ZEALAND ENTRANCE MIDHIRST MUDDY CLlFDEN ,.......-.--.... OIL SHAFT N01 WELL CREEK AUSTRALIA SECTION TARANAKI SECTION .' ... ' .. ' . ". ': :: . ~feet feet feet feet C0-": . ORBULINA UNIVERSA / 20 180 320 500. © ~ ORBULINA SUTURALIS 0 90 100 / 0 (@ Q ~ P. GlOMEROSA CIRCULARIS V 4 50 0 100 QCMJ ~ P. GlOME ROSA GlOMEROSA 8 60 235 0 @Q V P. GLOMEROSA CURVA ~ 32 60 825 150 V 988G. TRILOBUS BISPHERICUS ~ 172 no data 1774 950 Q Q Q V G. TRILOBUS TRILOBUS ~ 80 no data no data no data / fitJ8@ ~ G.~ CONNECTA no data no data no data / 152 IRREGULAR IRREGULAR ~ 4ft SAMDl.JW! f100ft SArtRlNG 8 SAMPLING G. WOODI WOOOICD SAMPLING TEXT FIGURE 2 Nine taxa of the Orbulilla lineage illustrated from specimens of the Muddy Creek section. All speci­ mens approximately X 32 and deposited in the collections of the New Zealand Geological Survey, Low­ er Hut!, under the numbers FP 1322-1335 inclusive. Stratigraphic separation of individual taxa re­ corded in feet in 4 named Miocene sequences. 136 JENKINS-EVOLUTION IN ORBULINA LINEAGE RESULTS Berggren (1968 in press : Table 38) has pub­ I. Evolutionary rate plotted against sediment lished a chronology of the Cenozoic. A correlation thicknesses. with the Australasian phylogeny of the Orbulilla The stratigraphic ranges of the 9 taxa of the ulliversa lineage indicates that Globigerilla woodi Orbulilla ulliversa lineage have been plotted against woodi appeared at about 28 m.y. B.P., Globigerill­ thicknesses