Contributors

Richard K. Olsson, Christoph Hemleben, William A. Berggren, Brian T. Huber, Editors

and MEMBERS OF THE PALEOGENE PLANKTONIC FORAMINIFERA WORKING GROUP*

*PALEOGENE PLANKTONIC FORAMINIFERA WORKING GROUP MEMBERS CONTRIBUTING TO PRODUCTION OF ATLAS: Dr. William A. Berggren (Chairman), Department of Geology & Geophysics,Woods Hole Oceanographic Institute, Woods Hole, MA 02543; Dr. Christoph Hemleben, Institute und Museum für Geologie und Paläontologie, Universität Tübingen, D-72076 Tübingen, Germany; Dr. Steven D'Hondt, School of Oceanography, University of Rhode Island, Kingston, RI 02881; Dr. Brian T. Huber, Department of Paleobiology, MRC NHB 121, National Museum of Natural History, Smithsonian Institution,Washington, D.C. 20560; Dr. D. Graham Jenkins (deceased), Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF1 3NP, United Kingdom; Dr. Chengjie Liu, Department of Geological Sciences, Rutgers University, New Brunswick, NJ 08903; Dr. Richard D. Norris, Woods Hole Oceanographic Institute, Woods Hole, MA 02543; Dr. Richard K. Olsson (Secretary), Department of Geological Sciences, Rutgers University, New Brunswick, NJ 08903; Dr. Paul N. Pearson, Department of Geology, University of Bristol, Queens Road, Bristol BS8 1RJ, U.K.; Dr. Fred Rögl, Naturhistorisches Museum, Paleontologisches Abt., Burggring 7, A1014 Vienna, Austria

Abstract

Sixty seven species of Paleocene planktonic foraminifera are described and illustrated: this includes three species of Eoglobigerina, four species of Parasubbotina, five species of Subbotina, two species of Hedbergella, ten species of Globanomalina, six species of Acarinina, twelve species of Morozovella, three species of Igorina, four species of Praemurica, one species of Guembelitria, one species of Globoconusa, three species of Parvularugoglobigerina, two species of Woodringina, six species of Chiloguembelina, one species of Rectoguembelina, and three species of Zeauvigerina. Taxonomic classification of normal perforate taxa are organized according to wall texture. Spinose cancellate genera include Eoglobigerina, Parasubbotina,and Subbotina; cancellate nonspinose genera include Igorinina and Praemurica; smooth-walled genera include Hedbergella and Globanomalina; and muricate genera include Acarinina and Morozovella. Taxonomic classification of microperforate taxa (including Guembelitria, Globoconusa, Parvularugoglobigerina, Woodringina, Chiloguembelina, Rectoguembelina, and Zeauvigerina) are organized according to test morphology.

Scanning electron microscope (SEM) images of type species described by Morozova in the collections of the Geological Institute, Academic Sciences [AN (GI)] in Moscow and the type material described by Subbotina in the collections of VNIGRI in St. Petersburg are shown in the atlas. Twelve species described by Morozova, nine species described by Subbotina, and one species described by Bykova are illustrated in the atlas. In addition, SEM images of 28 holotypes and two paratypes from the U.S. National Museum collections are included in the atlas, and neotypes for Globigerina compressa Plummer, 1926 and Globorotalia monmouthensis Olsson, 1961 are designated and illustrated with SEM images.

Paleobiogeographic maps showing the global distribution of 29 commonly occurring Paleocene taxa are included [in both the site and atlas], as well as figures showing the stratigraphic ranges of species by genus and stratigraphic first and last appearances. The biostratigraphic framework used [in the site and atlas] is the revised biostratigraphy given in Berggren et al., 1995. Wall texture and morphological relationships between species and genera form the basis of phylogenetic interpretations. This is discussed in the section on wall texture, classification, and phylogeny.

Introduction

The Paleogene Planktonic Foraminifera Working Group of the International Subcommission on Paleogene Stratigraphy, International Union of Geological Sciences was formed in 1987 following a meeting (organized by W.A. Berggren) at the British Petroleum Research Centre in Sunbury on Thames, U.K. It consists of foraminifera researchers interested in improving the understanding of Paleogene planktonic foraminiferal taxonomy and lineage phylogenies. The consensus of the meeting was that a concerted effort among workers was needed to unravel conflicting taxonomic usages of Paleogene taxa due to misunderstanding and lack of access to type collections, particularly in the former Soviet Union. The origins of many of the important biostratigraphic lineages was obscure so that the radiation of Paleogene planktonic foraminifera was poorly understood and, in fact as it turned out, some long held concepts proved to be erroneous. Some of the important questions included the origin of the basal Cenozoic radiation, the taxa involved and how to distinguish them, origin of the genus Acarinina, and the phylogeny of the morozovellids. In the following years important breakthroughs in research led to the evolution of the working group's understanding of taxonomy and the phylogeny of Paleogene planktonic foraminifera.

The first official meeting of the Paleogene Planktonic Foraminifera Working Group was held at the Institute of Geology and Paleontology at the University of Tübingen, Tübingen, Germany. In order to achieve a meaningful reconstruction of the taxonomy and phylogeny of Paleogene planktonic foraminifera the working group decided to focus on unraveling the origins and evolution of the earliest Paleocene (Danian) taxa so as to identify lineages of species which could be traced into the later Paleocene and ultimately through the Paleogene.

An important step in the understanding of Danian taxonomy came about with the visit by W.A. Berggren and F. Rögl to study type collections of Morozova housed in Moscow and with the study of Russian species in the collections of W.A. Berggren and H.P. Luterbacher. The work of Ch. Hemleben provided a preliminary understanding of a classification of living species which was based on whether or not spines were used in their biological behavior, a division which Parker (1962) clearly showed could be applied to living planktonic foraminifera based on the presence or absence of spines. His work focused on the identification in fossilized specimens of the spinose condition, since spines are used only when the individual is alive and are shed during gametogenesis. The presence of spine holes and spine bases in and on the chamber walls of fossil specimens indicated a spinose condition. The importance of wall structure was emphasized by Steineck and Fleisher (1978) in their seminal paper on a phylogenetically-based classification of planktonic foraminifera. An important breakthrough in using wall texture and structure in taxonomic classification of Paleocene planktonic foraminifera was announced at the 1989 meeting of the working group in Tübingen. This was the discovery by Ch. Hemleben and R.K. Olsson of spinose wall texture in specimens of Eoglobigerina eobulloides (Morozova) from Zone P in the Danian section at Millers Ferry, Alabama. This showed that the spinose condition had developed in planktonic foraminifera following the terminal Cretaceous mass extinction. It was an innovation, not present in Cretaceous planktonic foraminifera, and it meant that a phylogenetic classification based on wall texture might be applied to Danian planktonic foraminifera. In addition to this species, Parasubbotina pseudobulloides (Plummer) was subsequently shown to have a spinose wall texture. This discovery abruptly uprooted long held notions about Paleocene planktonic foraminiferal phylogenies (Bolli, 1957a; Blow, 1979) in which pseudobulloides was considered the ancestor of the nonspinose post-Danian muricate morozovellid radiation. The study by F.T. Banner (1989) on the planktonic foraminiferal genus Globanomalina clarified the taxonomy of the smooth-walled group of Paleocene planktonic foraminifera and showed that wall texture was highly important in tracing phylogeny and identifing lineages. His work identified the earliest Danian species, Globanomalina archeocompressa (Blow), as the first species of a smooth-walled nonspinose lineage. By the next meeting in 1990 in Tübingen the first Danian cancellate nonspinose species, Praemurica taurica (Morozova) was identified. It was now clear that Danian planktonic foraminifera consisted of four groups based on wall texture. These four groups had the same kind of wall texture as did the four groups of living planktonic foraminifera (Hemleben, et al., 1991). The wall textures are microperforate, normal perforate smooth-walled nonspinose, normal perforate cancellate nonspinose, and normal perforate cancellate spinose. Using this classification (Olsson et al., 1992) the new genera Parasubbotina and Praemurica were erected to represent two distinct Danian lineages.

During the 1991 and 1992 meetings in Tübingen and the 1993 meeting of the working group at the Cushman Laboratory, Smithsonian Museum, Washington, D.C. details of the Danian phylogeny had been worked out (Pearson, 1993) and the origin of the smooth-walled, cancellate nonspinose, and cancellate spinose groups from Hedbergella was demonstrated (Liu and Olsson, 1994). However, two opposing interpretations of the origin of the morozovellids remain unresolved. At issue is the derivation of this group from either Praemurica, the traditional view, or from Globanomalina which is a newly developed view. The traditional view, based on the original hypothesis of Bolli (1957a), is emphasized in the recent work of Berggren and Norris and Kelly et al. (1996). The alternate view, which is based on the studies of Hemleben and Olsson, emphasizes the development of the characteristic heavy pustulose wall texture of these groups from a smooth-walled Globanomalina ancestor. These views and their alternate phylogenetic interpretations are presented in the section on wall texture, classification, and phylogeny.

During the first meeting of the working group it was recognized that the microperforate wall texture separated a distinct group of planktonic foraminifera which dominate the lowest Danian assemblages. This group was viewed as opportunistic following the terminal Cretaceous mass extinction of planktonic foraminifera. It included Chiloguembelina, Globoconusa, Guembelitria, Parvularugoglobigerina, and Woodringina. Confusion over the difference between the normal perforate and microperforate species had led Brinkhuis and Zachariasse (1988) and Keller (1988) to erroneously identify microperforate specimens from the lower Danian at El Kef as normal perforate species (cancellate spinose and cancellate nonspinose). Thus, clarification and phylogeny of the microperforate group became an objective of our working group. By 1992 the phylogeny of the microperforates from the Cretaceous survivor species Guembelitria cretacea (Cushman) had been constructed (D'Hondt, 1991, Liu and Olsson, 1992). However, confusion with regards to the possible Cretaceous origin of Chiloguembelina prompted a careful morphologic comparison of Danian Chiloguembelina with the species Chiloguembelina waiparaenis Jenkins which, although described from the Danian of New Zealand, occurs in the uppermost Cretaceous of the Southern Ocean, Ocean Drilling Project (ODP) Site 758. At the 1993 meeting in Washington, D.C. it was shown that waiparaensis has a distinctive morphology which separates it from Chiloguembelina and that it is properly placed in the genus Zeauvigerina which has a Cretaceous to Paleocene range. Zeauvigerina, which is restricted to the southern latitudes, is tentatively placed in the Heterohelicidae as it does not have a phylogenetic relationship with the Guembelitriidae (Huber and Boersma, 1994).

Work on the origin and phylogeny of Acarinina by W.A. Berggren and R.D. Norris led to an important revision of Paleocene Zone P4. They showed that the consecutive appearances of A. subsphaerica Subbotina and A. soldadoensis (Brönnimann) allow Zone P4 to be divided into three subzones. This plus other refinements has resulted in an updated version of the Berggren and Miller (1988) zonation of the Paleocene (Berggren and Norris, 1995) which is summarized in the atlas.

An important development in the clarification of Russian species appears in Plates 8-12 of the atlas where many holotypes are illustrated by SEM for the first time. F. Rögl was able to borrow the type material described by Morozova in the collections of the Geological Institute, Academic of Sciences (GI)(AN) in Moscow and the type material described by Subbotina in the collections of VNIGRI in St. Petersburg and obtain low KV SEM images of these species. One big surprise is that the widely used but poorly understood species Globigerina fringa Subbotina has a coarsely cancellate wall and thus is not closely related to any of the earliest Danian taxa. The species, in fact, appears to be described from an upper Danian stratigraphic level and has affinities with Subbotina cancellata. This illustrates the pitfalls for workers who use poorly illustrated drawings of Russian species in identifying taxa for biostratigraphic studies. These SEM images of Russian types and the personal observations of Russian taxa by W.A. Berggren and F. Rögl have greatly improved the understanding of these species, their taxonomy and their synonymy. In addition to the SEM images of Russian types, low KV SEM images taken by B.T. Huber of types in the Cushman collections are also included in the atlas. The atlas also includes SEM images of topotypes of Globanomalina australiformis (Jenkins), Hedbergella holmdelensis Olsson, Hedbergella monmouthensis (Olsson), Morozovella acutispira (Bolli and Cita), Woodringina hornerstownensis Olsson, and specimens of Parvularugoglobigerina eugubina (Luterbacher and Premoli Silva) from the type level at Gubbio, Italy.

There is a newly revised zonation for the Paleocene (link to datum page) with range charts showing the maximum known range of each species organized according to generic classification (link to genus range chart page) which, in turn, is organized by wall texture groups. Other range charts show the order of the first appearances of taxa (link to First Occurrence range chart) and the last appearances of taxa (link to Last Occurrence range chart). The section on taxonomy includes the species considered valid by the working group and includes a synonymy of species considered to be junior synonyms by personal observation of working group members. Several images of the relevant species are included in this site in order to illustrate the range of morphologic variability of the species. Species that are obscure or are poorly known are not included because their validity is unproven. These species names are mentioned in the taxonomic discussion under the species which is considered a probable senior synonym. Paleobiogeographic maps showing the known distribution of nominate species representative of each genus is included under that species. Reconstruction of paleobiogeographic maps was generated using the PGIS/MacTM software package. Land-sea distributions are modified from Barron (1987). Occurrences are plotted only for well-documented identifications either by SEM showing unequivocal images, or by unequivocal drawings, or by personal observation of a working group member. Lists of identified species without illustrations were not used. Interested workers can update these maps through their own research.

The working group was saddened by the sudden death of Graham Jenkins in August 1995. He played an active role at the meetings of the working group in his capacity as secretary of the International Subcommission on Paleogene Stratigraphy and was valued for his expert knowledge of Paleocene Southern Ocean planktonic foraminifera.

Acknowledgements

The Paleogene Planktonic Foraminiferal Working Group (PPFG) is indebted to Hans Bolli (Zurich), Walter Blow (deceased) and Nina Subbotina (deceased) whose pioneering contributions to the study of Paleogene planktonic foraminifera spanned nearly a half-century from the mid-30s to the mid-80s of this century and laid the groundwork and provided the inspiration for the taxonomic revision which we present in this Atlas. The Paleogene Planktonic Foraminifera Working Group was organized in 1987 at a meeting at the British Petroleum Research Centre in Sunbury on Thames, U.K. We thank Dr. J. Athersuch of BP for hosting this important first meeting. The next five meetings of the working group were held at the Institute und Museum für Geologie und Paläontologie, Universität Tübingen, Tübingen, Germany where Dr. Ch. Hemleben graciously hosted these meetings. The invaluable logistical assistance of J. Breitinger and D. Mühlen at these meetings is deeply appreciated. We thank H. Hütteman for his assistance in examining specimens in the scanning electron microscope and Dr. H.P. Luterbacher, Universität Tübingen, for access to his collections of Russian species and samples from the type level of the "Globigerina" eugubina Zone. Dr. B.T. Huber hosted the seventh meeting of the working group at the National Museum of Natural History, Smithsonian Institution in Washington, D.C. and Dr. R.K. Olsson hosted the final meeting at Rutgers University, Piscataway, New Jersey.

Discussions with Nina Subbotina (St. Petersburg, deceased),Valery Krasheninnikov (Moscow) and Khalil Alliyula (Baku, deceased) were helpful in elucidating problems of taxonomy among species housed in the collections of VNIGRI (St Petersburg), AN (GI) (Moscow) and AN (GI) (Baku), respectively, during various visits (1958-1988) by W.A. Berggren. We appreciate the assistance of S.P. Jakovleva, VNIGRI, St. Petersburg and N. Muzylöv, Geological Institute, Russian Academy of Sciences, Moscow to F. Rögl in obtaining a loan of Russian type material. Scanning electron micrographs (SEM) of U.S. National Museum primary types shown were taken and mounted by B.T. Huber. Scanning electron microscopy by S. D'Hondt at the University of Rhode Island was assisted by P. Johnson.

Material used in preparing scanning electron micrographs of Paleocene species were supplied by members of the working group. Many of the specimens were selected from personal collections and from Deep Sea Drilling Project (DSDP) and ODP sites. Micrographs for wall texture and preservation are from the collections of Dr. Ch. Hemleben. We deeply appreciate the indefatigable work of H. Hüttemann, Universität Tübingen, in taking thousands of micrographs needed for composing the plates for the atlas. These plates were prepared in the laboratory of Ch. Hemleben. We thank J. Breitinger, D. Mühlen, and B. Rödiger for their assistance. We acknowledge the opportunity to investigate specimens collected by W. Weiss.

The following research support is acknowledged: W.A. Berggren (Marine Geology and Geophysics Branch, Ocean Sciences Division of NSF), Ch. Hemleben (Deutsche Forschungsgemeinschaft (DFG) He 697/15), S. D'Hondt (supported in part by the Earth Sciences Division of NSF), R.D. Norris (Earth Sciences Division of NSF), R.K. Olsson (Department of Geological Sciences, Rutgers University), F. Rögl (Naturhistorisches Museum Wien). We thank the Ocean Drilling Program for supplying samples used in this study.

A number of scientists with interest in Paleogene planktonic foraminifera attended some of the meetings and participated in the discussions of the working group. They include: A.J. Arnold, Florida State University, Tallahassee, Florida, U.S.A.; F.T. Banner, University College of London, London, U.K.; C. Benjamini, Ben Gurion University of the Negev, Beer Sheva, Israel; A. Boersma, Microclimates Research Consultants, Stony Point, N.Y.; R. Corfield, University of Oxford, Oxford, U.K.; R.L. Fleisher, Chevron U.S.A. Inc., Houston, Texas; S. Gaboarrdi, University of Milano, Milan, Italy; A. v. Hillebrandt, Technical University of Berlin, Berlin, Germany; C. Kelly, University of North Carolina, North Carolina, U.S.A.; E. Kitchell, University of Michigan, Michigan, U.S.A.; Q. Li, Imperial School of Science & Technology, London, U.K.; H. Luterbacher, Universität Tübingen, Tübingen, Germany; E. Molina Martinez, University of Zaragoza, Zaragoza, Spain; N. MacLeod, The Natural History Museum, London, U.K.; I. Premoli Silva, University of Milano, Milan, Italy, S. Radford, Imperial School of Science & Technology, London, U.K.; S. Spezzaferri, University of Milano, Milan, Italy and S. Sturrock, British Petroleum Ltd., Sunbury, U.K.

Biostratigraphy

The use of planktonic foraminifera in biostratigraphy may be said to be an essentially post-World War II phenomenon (although there were several pre-war contributions of less than lasting value) which resulted from the recognition of their usefulness in local and regional biostratigraphic zonation and correlation. These studies were often, but not exclusively, connected with exploration for petroleum, particularly in the North Caucasus, Crimea, Tadzhik Depression and other areas of the SW (former) Soviet Union (Subbotina, 1947, 1953; Morozova, 1959, 1961; Alimarina, 1962, 1963; Leonov and Alimarina, 1961) and Caribbean region (Brönnimann, 1952; Bolli, 1957a,b; and Gulf and Atlantic Coastal Plain regions (Loeblich and Tappan, 1957a). Various biostratigraphic zonal schemes were developed by the authors cited above, among others, and these have been rapidly ensconced in the classic biostratigraphic hagiography of the past half century. Since the advent of the DSDP (1968) and its successor program the ODP (1985-present) the various zonal schemes have found widespread application in regional and global biostratigraphic studies. In the following section we present a brief review of the major Paleocene biostratigraphic zonal schemes developed over the past 50 years . It should be remembered that some of these schemes were developed as part of a larger zonal scheme- the Paleogene or the Cenozoic -so that reference to the larger framework is unavoidable in certain instances.

A detailed zonal biostratigraphy of the Danian and Montian Stages (as recognized ) in the Crimea, North Caucasus and "Boreal" areas (Russian Platform and Precaspian Basin) was developed by Morozova (1959, 1960). In these, and subsequent studies (Morozova, 1961) she recognized several taxa that have become important in lower Paleocene (lower Danian Stage) biostratigraphy such as Eoglobigerina eobulloides and Globigerina taurica .

Coarsely muricate acarininids have figured prominently in mid-late Paleocene zonal biostratigraphies, particularly that of the "official" Paleogene zonation of the former Soviet Union (Permanent Interdepartmental Stratigraphic Commission for the Paleogene of the USSR, 1963), due to the general paucity of keeled morozovellids (acuta, velascoensis), and globanomalinids (pseudomenardii) in the formation(s) above the Morozovella angulata-conicotruncata bearing strata in the northern foothills of the Caucasus Mountains (Subbotina, 1953; Alimarina, 1963) and the SW Crimea (Morozova, 1959, 1960). This latter scheme would appear to have drawn heavily upon the detailed studies by the authors cited above as well as those of Shutskaya (1956: Precaucasus; 1962: Crimea, Precaucasus and Transcaspian region; 1965:The taxonomic treatment of taxa is not up-to-date and the identification of some taxa shouldn't be attempted when preservation is so poor. Turkmenistan). Shutskaya subsequently presented a detailed synthesis of her decade long studies in the SW Soviet Union, including a detailed zonal scheme for the Paleocene-lower Eocene in her doctoral thesis (1965) and then concluded with an exhaustive historical overview of the Paleogene (bio)stratigraphic succession and zonal characteristics of the Crimea, northern Precaucasus and western part of Central Asia (1970a). In the latter work she included 40 plates with detailed illustrations of the faunal content (planktonic and benthic taxa) of each Paleocene and lower Eocene zone from each region which makes it possible to understand better the basis for biostratigraphic subdivision of the Paleogene of the SW Soviet Union. It also allows correlation of her zonal scheme with that subsequently proposed in the West over the past 35 years. Krasheninnikov (1965, 1969) also made significant contributions to Paleocene biostratigraphy of the SW (former) Soviet Union as well as other (sub)tropical areas of the world.

Paleocene planktonic foraminiferal biostratigraphy in the West was essentially baptized in the form of a detailed zonation developed for the Paleocene and lower Eocene of Trinidad by Bolli (1957a; modified in 1966) which was followed soon after by a zonal scheme developed for (sub)tropical regions by Berggren (1969a, 1971a; modified and (re)defined by Berggren and Miller, 1988) and Blow 1979). Premoli Silva and Bolli (1973) made minor changes to the earlier zonation of Bolli (1957) with the insertion of the Globorotalia edgari Zone between the Globorotalia velascoensis Zone (below) and the G. rex (=G. subbotinae ) Zone (above; see Toumarkine and Luterbacher, 1985). Jenkins (1971) formulated a relatively broad zonal biostratigraphic scheme for the Paleocene (as part of a larger Cenozoic study) of New Zealand. With the recognition that Paleocene low latitude, (sub)tropical zonation(s) are not fully applicable at high latitudes, Stott and Kennett (1990) developed a zonal biostratigraphy for high (austral) latitudes of the Antarctic.

We have adopted the following five-fold (sub)tropical biostratigraphic zonation of the Paleocene based on studies of Berggren and Norris (1993) who redefined the zonal boundary definitions of Zones P3a/b, P4/5 and proposed a threefold subdivision of Zone P4. This zonal biostratigraphy has been more fully defined and elaborated upon in Berggren et al. (1995). The definition of the five Paleocene zones (and their subdivisions), magnetochronologic calibration, and estimated age is presented below. Additional information on the characterization of these zones may be found in Berggren et al. (1995). Modifications to this scheme have been proposed by Lu and Keller (1995) based on their study of DSDP Site 577. Additional information on the history of Paleogene/Paleocene planktonic foraminiferal biostratigraphy may be found in Berggren and Miller (1988).

P0. Guembelitria cretacea Partial Range Zone (P0; Keller, 1988, emend. of Smit, 1982)

Definition: Biostratigraphic interval characterized by the partial range of the nominate taxon between the Last Appearance Datum (LAD) of Cretaceous taxa (Globotruncana, Rugoglobigerina, Globigerinelloides, among others) at the K/P boundary as delineated by the essentially global iridium spike and the First Appearance Datum (FAD) of Parvularugoglobigerina eugubina.

Magnetochronologic calibration: Chron C29r (late part)

Estimated age: 65.0-64.97 Ma; earliest Paleocene (Danian)

Pa. Parvularugoglobigerina eugubina Total Range Zone ( Liu, 1993, emend. of Pa of Blow, 1979; Luterbacher and Premoli Silva, 1964)

Definition: Biostratigraphic interval characterized by the total range of the nominate taxon

Magnetochronologic calibration: Chron C29r (later part)

Estimated age: 64.97-64.9 Ma; earliest Paleocene (Danian)

P1. Parvularugoglobigerina eugubina-Praemurica uncinata Interval Zone (P1; defined in Berggren et al., 1995, emend. of Berggren and Miller, 1988).

Definition: Biostratigraphic interval between the LAD of Parvularugoglobigerina eugubina and the FAD of Praemurica uncinata.

Magnetochronologic calibration: Chron C29r (later part)-Chron C27n(0)

Estimated age: 64.9-61.2 Ma; early Paleocene (Danian)

P1a. Parvularugoglobigerina eugubina-Subbotina triloculinoides Interval Subzone (P1a; defined in Berggren et al., 1995; emendation of Pa. pseudobulloides Subzone (P1a) in Berggren and Miller, 1988)

Definition: Biostratigraphic interval between the LAD of Parvularugoglobigerina eugubina and the FAD of Subbotina triloculinoides

Magnetochronologic calibration: Chron C29r (later part)-Chron C29n (mid part)

Estimated age: 64.9-64.5 Ma; early Paleocene (early Danian)

P1b. Subbotina triloculinoides-Globanomalina compressa/Praemurica inconstans Interval Subzone (P1b; defined in Berggren et al., 1995; emendation of, but equivalent to, Subzone P1b in Berggren and Miller, 1988)

Definition: Biostratigraphic interval between the FAD of Subbotina triloculinoides and the FADs of Globanomalina compressa and/or Praemurica inconstans

Magnetochronologic calibration: Chron C29n (mid part)-Chron C28n (mid part)

Estimated age: 64.5-63.0 Ma

P1c. Globanomalina compressa/Praemurica inconstans-Praemurica uncinata Interval Subzone (P1c; defined in Berggren et al., 1995; emendation of, but equivalent to, Subzone P1c in Berggren and Miller, 1988).

Definition: Biostratigraphic interval between the FAD of Globanomalina compressa and/or Praemurica inconstans and the FAD of Praemurica uncinata

Magnetochronologic calibration: Chron C28n (mid)-Chron C27n(o)

Estimated age: 63.0-61.2 Ma

P2. Praemurica uncinata-Morozovella angulata Interval Zone (P2; defined in Berggren et al., 1995; emend. of, but biostratigraphically equivalent to, Zone P2 in Berggren and Miller, 1988)

Definition: Biostratigraphic interval between the FAD of Praemurica uncinata and the FAD of Morozovella angulata

Magnetochronologic calibration: Chron C27n(o)-Chron C27n(y)

Estimated age: 61.2-61.0 Ma; late early Paleocene (late Danian)

P3. Morozovella angulata-Globanomalina pseudomenardii Interval Zone (P3, defined in Berggren et al., 1995; emendation of Zone P3 in Berggren and Miller, 1988).

Definition: Biostratigraphic interval between the FAD of Praemurica angulata and the FAD of Globanomalina pseudomenardii

Magnetochronologic calibration: Chron C27n(y)-Chron C26r (mid

Estimated age: 61.0-59.2 Ma; late Paleocene (Selandian)

P3a. Morozovella angulata-Igorina albeari Interval Subzone (P3a; defined in Berggren et al., 1995)

Definition: Biostratigraphic interval between FAD of Morozovella angulata and FAD of Igorina albeari

Magnetochronologic calibration: Chron C27n(y)-Chron C26r (early)

Estimated age: 61.0-60.0 Ma; early late Paleocene (Selandian)

P3b. Igorina albeari-Globanomalina pseudomenardii Interval Subzone (P3b; defined in Berggren et al., 1995)

Definition: Biostratigraphic interval between FAD of Igorina albeari and the FAD of Globanomalina pseudomenardii

Magnetochronologic calibration: Chron C26r (early)-Chron C26r (mid)

Estimated age: 60.0-59.2 Ma; late Paleocene (Selandian)

P4. Globanomalina pseudomenardii Total Range Zone (P4; Bolli, 1957a) Definition: Biostratigraphic interval of the total range of the nominate taxon, Globanomalina pseudomenardii

Magnetochronologic calibration: Chron C26r (mid)-Chron C25n(y)

Estimated age: 59.2-55.9 Ma; middle part of late Paleocene (late Selandian-Thanetian)

P4a. Globanomalina pseudomenardii/Acarinina subsphaerica Concurrent Range Subzone (P4a; defined in Berggren et al., 1995)

Definition: Biostratigraphic interval characterized by the concurrent range of the two nominate taxa between the FAD of Globanomalina pseudomenardii and the LAD of Acarinina subsphaerica

Magnetochronologic calibration: Chron C26r (mid)-Chron C25r (early)

Estimated age: 59.2-57.1 Ma; late Paleocene (latest Selandian-early Thanetian)

P4b. Acarinina subsphaerica-Acarinina soldadoensis Interval Subzone (P4b: herein defined)

Definition: Biostratigraphic interval from the LAD of Acarinina subsphaerica to the FAD of Acarinina soldadoensis

Magnetochronologic calibration: Chron C25r (early)-Chron C25r (late)

Estimated age: 57.1-56.5 Ma; late Paleocene (Thanetian)

P4c. Acarinina soldadoensis-Globanomalina pseudomenardii Concurrent range Subzone (P4c; defined in Berggren et al., 1995)

Definition: Biostratigraphic interval containing the concurrent range of the nominate taxa from the FAD of Acarinina soldadoensis to the LAD of Globanomalina pseudomenardii

Magnetochronologic calibration: Chron C25r (late)-Chron C25n(y)

Estimated age: 56.5-55.9 Ma; late Paleocene (late Thanetian)

P5. Morozovella velascoensis Interval Zone (P5; Bolli, 1957a; P5 and P6a of Berggren and Miller, 1988)

Definition: Biostratigraphic interval between the LAD of Globanomalina pseudomenardii and the LAD of Morozovella velascoensis

Magnetochronologic calibration: Chron C25n(y)-Chron C24r (mid)

Estimated age: 55.9-54.7 Ma; latest Paleocene-earliest Eocene (latest Thanetian-earliest Ypresian)

Wall Texture, Classification, and Phylogeny

The recovery of early Paleocene planktonic foraminifera following the end Cretaceous mass extinctions led to fundamental changes in the wall structure of the test, changes linked to the way in which the earliest Paleocene species adapted to the water mass environment. These changes in wall structure, consequently, reflect biological activity. Five species are known to have survived into the Paleocene. We believe that the planktonic foraminiferal species that came to occupy the Paleocene oceans were derived from three survivors which rapidly gave rise to distinct lineages. The structural differences in the test wall allows basic groups to be recognized. Two groups are separated by pore size, one being microperforate (pore diameter < 1 µm) and the other normal perforate (pore diameter 2-7 µm). The microperforate species which evolved from the survivor-species Guembelitria cretacea have been dealt with in various studies (D'Hondt, 1991; Liu and Olsson, 1992). In the earliest Paleocene (Danian) trochospiral and biserial microperforate taxa evolved from a triserial taxon. Although there are fundamental changes that occurred in the shape of the test, the wall structural changes are moderate (a thin wall pierced by micropores, and pustule growth in rounded mounds or short, sharp protuberances).

Wall structure changes in normal perforate planktonic foraminiferal were often quite dramatic. Most notable is the development of a cancellate wall which is a distinctive and diagnostic feature of the Cenozoic. This feature which developed in two groups, one with spines and the other without spine, indicates that the biological activities of planktonic species that possessed this structure were significantly different from the biological activities in Cretaceous species where this structure is absent. Another dramatic wall structural change was the development of the "pseudospinose" (Benjamini and Reiss, 1979) or "muricate" wall (Blow, 1979), identified by a heavy pustulose growth. All the taxa in this group can be separated phylogenetically on the basis of their distinctive pustulose wall texture. Perhaps the most dramatic change in wall structure was the development of spines which was accompanied by growth of a cancellate wall. Wall growth in species using spines is different from wall growth in nonspinose pustule bearing species. Pustules are layered structures which form during ontogeny as part of the wall in contrast to spines which are elongated single crystals planted in the shell wall (Hemleben, 1969; Hemleben, et al., 1991). Pustulose growth is rare in spinose species. Due to the development of these distinctive wall structures Paleocene normal perforate planktonic foraminifera can be classified and organized in phylogenetic lineages.

A classification based on functional morphology is somewhat more complex than one based on simple test morphology since it presumes that one can correctly interpret the function of a structure in an extinct species. In the Paleocene this is made easier because direct comparison can be made to living planktonic species in which there is much data on the function of test morphology and biological activity (Hemleben et al., 1977, 1985, 1991). The basic underlying bilamellar wall concept of Reiss (1957) can be applied to all known Paleocene planktonic foraminiferal species. The introduction of spines in the earliest Danian allowed planktonic foraminifera to develop a different habit of food gathering and to invade different habitats. It is possible that some species may have collected symbionts as is suggested by the carbon isotopic studies of D'Hondt and Zachos (1993) on Eoglobigerina eobulloides. Thus, photosymbiosis may have developed along with the evolution of some of the first spinose planktonic species of the Cenozoic. Species having symbionts would have been bound to the photic zone.

The nonspinose planktonic foraminifera are distinguished by two basic types of wall texture, smooth-walled and cancellate-walled. In the smooth-walled type pustules may be absent, sparsely developed, or heavily developed as is observed in modern Globorotalia. Heavy pustule development in the Paleocene led to the "muricate structure" which characterizes the genera Acarinina and Morozovella. The cancellate texture develops by lateral growth of small pustules into smooth ridges upon which additional pustules may grow. This texture is observed in the modern Neogloboquadrina dutertrei.

It would appear, then, that some adaptations that evolved in Paleocene species of planktonic foraminifera are similar, if not identical in some cases, to the adaptations that are shown by living species of planktonic foraminifera. Since wall texture reflects the adaptive strategies exhibited in the biological activity of living species it may be an important guide to phylogenetic study. We regard this relationship as a unifying concept in the classification and phylogenetic study of Cenozoic planktonic foraminifera. Although more work needs to be done on wall texture and morphologic change in the evolution of Paleogene planktonic species, it seems clear from the results of the Paleogene Planktonic Foraminifera Working Group that wall texture provides a guide to understanding the evolution and phylogeny of Paleocene planktonic foraminiferal species and for their classification.

Globorotaliid Wall Texture

The globorotaliid type, which includes the juvenile up to the neanic stage (Brummer et al., 1986), is characterized by a smooth nonspinose wall with more or less scattered pustules. Pustules increase in number during ontogeny, serving as anchor points for rhizopods. During continued growth more pustules form on the center of the spiral side, around the aperture and if a keel is present on the keel. The last growth stage may be characterized by a coarse crystal growth or pustules may coalesce to form a coarse crystalline outer layer. The abundance of pustules varies from species to species. The inter-pustule area is usually smooth with no or very low relief. Some typical living representatives of this type are Globorotalia hirsuta, G. menardii, G. truncatulinoides and others (Hemleben et al., 1977, 1985, 1991) and their ancestors. The Paleocene genus Globanomalina has this type of wall texture. The smooth-walled genus Globanomalina was derived from the late Maastrichtian hedbergellid, Hedbergella holmdelensis, the first species being G. archeocompressa . In this transition the morphologic characters of the descendant species (compressed test with an imperforate peripheral band and an extraumbilical aperture, bordered by a narrow lip) are derived from the ancestral species. The wall of H. holmdelensis is smooth with scattered small pustules on the chamber walls. In G. archeocompressa the pustules become confined to the umbilical area rather than being scattered over the entire test. A change to somewhat more angular shaped chambers accompanies the transition. Although the change in overall morphology is small, the wall becomes distinctly smooth, a character that identifies species of Globanomalina and its possible descendant, Pseudohastigerina.

Muricate Wall Textures

In the Paleocene, a heavily pustulose wall texture occurs in the genera Acarinina and Morozovella (Plates 39-55). The test wall is characterized by large very coarse pustules which may cover the entire test, be concentrated on the umbilical shoulders, or be confined to the periphery of the test forming a keel (Plate 4, Figures 14, 15; Plate 5, Figures 1-4). The pustules grow on a smooth globorotaliid surface. In the first species of Acarinina, A. strabocella, the early ontogenetic stage has a rather smooth wall resembling that of modern globorotaliid species; but later in ontogeny (or chamber calcification) the typical pustule pattern appears, which is similar to that in modern Globorotalia inflata (Plate 3, Figures 3, 4, 7). The pustules are spread over the entire test but they are especially large and thick in front of the aperture. However, they are arranged in lines leading towards the aperture (see Plate 43, figure 4). This development is a short step to the more typical heavily pustulose acarininids in which the pustules become broad and elongate (Plates 39-42, 44). The wall texture develops by the growth of conical to blade-like pustules at triple points between the pores. As these pustules grow larger they coalesce into larger structures which give the muricate wall a somewhat cancellate appearance. Pustule enlargement is greatest around the umbilicus and often completely closes off the pores.

In the evolution of Morozovella two groups of species are separated by different types of muricate wall texture. The muricate wall texture in the Morozovella aequa line of species develops by growth of conical pustules of various sizes at triple points between pores on rather smooth chamber walls (Plates 47-49, 54). Heavier pustule growth occurs on the umbilical shoulders of the chambers and along the test periphery forming an imperforate muricate keel in some species. In the Morozovella velascoensis line of species the surface of the chambers are smooth (Plates 45, 46, 50-52, 55). Very heavy conical pustule growth occurs on the umbilical shoulders of the chambers and along the axial periphery of the test forming a strong, imperforate muricate keel. Scattered small pustules also may occur on the chamber surfaces. Extensions of the muricate keel occur on the spiral side of the test along the chamber sutures and the spiral suture. Morozovella is further characterized by development of conical-shaped chambers.

Neogloboquadrinid Wall Texture (Praemuricate)

This type of wall texture is seen in the living species Neogloboquadrina dutertrei (Plate 5, Figures 5-11). The growth pattern during ontogeny consists of the development of longer or shorter subparallel low ridges of plate-like crystals, often oriented towards the aperture (Plate 5, Figures 9, 10). They become more and more prominent while short ridges connecting the subparallel ones start to grow and, eventually, form a honeycomb cancellate wall structure (Hemleben et al., 1991). The short ridges are less developed and may extend only part way from one elongate ridge to the other (Plate 5, Figures 9, 10). It is a very common structure in Paleogene and Neogene planktonic foraminifera. This type of wall texture occurs in the Paleocene genera Igorina and Praemurica (Plates 56-62). A calcite crust (Plate 5, Figures 8, 11) which is a normal feature in Neogloboquadrina has not yet been observed in Paleocene species, probably due to warmer Paleocene surface waters since it is a feature usually developed in cold waters of the modern ocean. However, in the modern N. dutertrei as pustule growth becomes more and more prominent the test wall becomes thicker and encrusted, a feature that is also observed in Igorina (Plates 56-58). In Zone P0 the transition from the ancestral Maastrichtian Hedbergella monmouthensis to Praemurica involves the buildup of subparallel pustulose ridges and short connective ridges, thus producing the cancellate texture (Plate 5, Figures 12, 18; Plate 6, Figures 1-4). In Praemurica taurica (Plate 61), the first Praemurica species, the test remains very low trochospiral with an extraumbilical aperture but selection is to a H. monmouthensis morphotype with a lower rate of chamber expansion in the ultimate whorl (six-chambered test). In order to avoid confusion with the term neogloboquadrinid we propose the use of praemuricate for Paleocene taxa with this wall texture.

Spinose Wall Texture

The spinose habit indicates that a group of new planktonic foraminifera intruded into the carnivorous food niche. The food catching process is supported by long calcitic spines along which flows the rhizopodial cytoplasm. Actively swimming zooplankton are snared and held without losing control of a struggling zooplankton organism. The spines are separated from the wall and planted like telephone poles (Plate 1, Figures 3, 4, 7-20). During the reproductive process (gametogenesis) the spines are dissolved, leaving a vacated spine hole as an indication of the spinose condition, and gametogenetic calcite is deposited along the interpore ridges (Plate 2, Figures 2-16). More fundamental changes in wall texture and test morphology took place in the transition from Hedbergella monmouthensis to the spinose genera Eoglobigerina and Parasubbotina (Plates 18-23). The fundamental morphologic characters (trochospiral test with an extraumbilical aperture bordered by a narrow lip) are maintained in the descendent species but the evolution of wall texture involves the innovation of a cancellate spinose wall. In H. monmouthensis the wall is lightly pustulose throughout the test and low depressions or primitive pore pits occur in the chamber walls especially surrounding the umbilicus (Plate 31). The test is a very low trochospiral with rapidly inflating chambers in the ultimate whorl, but as noted in Liu and Olsson (1994), there is a range of morphotypes that show 1) a reduced rate of chamber size increase with generally six chambers in the ultimate whorl, and 2) a moderately elevated trochospiral test with five chambers in the ultimate whorl. In the transition to the first spinose species, Eoglobigerina eobulloides, the moderately elevated trochospiral test becomes weakly cancellate and spinose (Plate 19). The cancellate texture is enhanced by gametogenetic calcification. Due to the moderately elevated trochospiral test the aperture shifts to a more umbilical position and is only slightly extraumbilical. In the derivation of Parasubbotina (Plates 21, 22) the rate of chamber increase is much more rapid than in Eoglobigerina, which produces a very low trochospiral test with large globular chambers in the ultimate whorl. The wall becomes weakly cancellate and spinose. The aperture remains extraumbilical. Subbotina (Plate 2, Figures 3-6, 15, 16; Plates 24-29) evolves from Eoglobigerina by a reduction in the number of chambers in the final whorl and a shifting of the aperture towards an umbilical position and by the development of a stronger cancellate wall texture.

Preservation and Diagenesis

Preservation of fossil planktonic foraminifera plays an important role in taxonomic and phylogenetic studies. The effect of the lysocline and the carbonate compensation depth controls the preservation or partial preservation of an assemblage of planktonic foraminifera. Absence of a species could be due to its greater susceptibility to dissolution than other species, thereby leading directly to loss of information. Preservation of planktonic foraminifera can be loosely measured by visual inspection under the light microscope and more recently by the SEM. It is especially important to assess the degree of preservation of foraminifera tests in isotopic analyses, but it is also important in various other studies utilizing planktonic foraminifera. For instance, in taxonomic and phylogenetic studies, the degree of preservation may appear to be excellent (pristine) preservation under the light microscope but may actually be rather poor when examined in the SEM under high magnification. In working out phylogenetic lineages it is important to be able to recognize the original wall texture in order to assess whether an ancestor-descendant relationship exists. Preservation is an important factor in census work where many individuals of species have to be accurately identified for the data to be meaningful. Census work should not be attempted where the tests of foraminifera are heavily recrystallized and overgrown, thus making identification very subjective due to similar morphology of different species. Plate 7 illustrates common types of diagenetic alteration of a planktonic foraminiferal test.

Recrystallization can vary from slight to heavy (Plate 7, Figures 1, 2, 5-8, 10-15). If the degree of recrystallization is substantial, subhedral and euhedral calcite crystals form and obscure the original wall (Plate 7, figure 12). Overgrowth of calcite (Plate 7, Figures 4, 8, 10) further obscures the original wall. Corrosion of a test removes the outer wall layers (Plate 7, Figures 3, 5, 6) thereby destroying the original wall texture. Dissolution (Plate 7, Figures 3, 9) may destroy parts of the test wall leaving holes or strip away outer wall layers, altering the appearance of the specimen. Accurate identification is precluded under such circumstances. Plates 1-6 illustrate well preserved original wall texture which can be used as a guide in assessing the effects of diagenesis on samples of fossil planktonic foraminifera.

Phylogeny

The phylogeny of the normal perforate Paleocene planktonic foraminifera is shown in Text-figure 5 and that of the microperforate is shown in Text-figure 6. Comments on the phylogeny of the microperforates are given in the section on taxonomy (also see D'Hondt, 1991; Liu and Olsson, 1992). The lineages of the normal perforates based on wall texture study is given below with comments on the major morphologic changes that occurred in the evolution of the species in each lineage.

SPINOSE LINEAGES

Cancellate Lineages Eoglobigerina E. eobulloides - E. edita - E. spiralis lineage characterized by: 1) a cancellate spinose test. 2) development of a higher trochospiral test in E. edita and E. spiralis. 3) a reduced rate of chamber expansion in E. edita compared to E. ebulloides. 4) a more strongly developed cancellate wall which is enhanced by gametogenetic calcification in E. edita and E. spiralis.

E. eobulloides - Subbotina lineage characterized in the transition to Subbotina by: 1) a more strongly developed spinose cancellate wall. 2) a reduced number of chambers in the ultimate whorl. 3) development of a tripartite test due to a more rapid rate of chamber size increase. 4) a more umbilically directed aperture in Subbotina. Note: in E. eobulloides the aperture has an umbilical to slightly extraumbilical position due to the moderately elevated trochospire. In Subbotina the increase in rate of expansion of chambers causes the aperture to shift to a more umbilical position. This trend culminates in S. triloculinoides by producing a large ultimate chamber with an umbilically directed aperture. The lip maintains its position relative to the apertural opening. With a greater expansion rate of chambers, the initial moderately elevated coil is enveloped by the expanding chambers thus producing a test with an apparent low trochospire.

Parasubbotina P. aff. pseudobulloides - P. pseudobulloides - P. varianta lineage characterized by: 1) a weakly developed cancellate spinose wall in P. aff. pseudobulloides. 2) development of a pronounced cancellate spinose wall which is enhanced by gametogenetic calcification in P. pseudobulloides. 3) an increase in test size in P. pseudobulloides. 4) a decreased number of chambers in the ultimate whorl in P. varianta.

P. varianta - P. variospira lineage characterized by: 1) an increased expansion of the chamber coil and a shift to a moderately elevated trochospire in P. variospira. 2) a decreased rate of expansion of chambers in P. variospira. 3) a test size increase in P. variospira. 4) development of toothlike apertural lips in P. variospira. Note: Parasubbotina is distinguished from Subbotina by its very low trochospire, greater number of chambers in the ultimate whorl, and the umbilical extraumbilical aperture.

Subbotina S. trivialis - S. aff. cancellata - S. cancellata - S.velascoensis lineage characterized by: 1) development of a coarsely cancellate spinose wall S. cancellata. 2) a more rapid rate of chamber size increase which ultimately closes the umbilicus in S. velascoensis. 3) test size increase in the lineage. 4) development of flattened, oval-shaped chambers in S. velascoensis.

S. trivialis - S. triloculinoides lineage characterized by: 1) a more strongly developed cancellate spinose wall in S. triloculinoides. 2) a more rapid rate of chamber size increase which ultimately closes the umbilicus in S. triloculinoides. 3) a test size increase in S. triloculinoides.

S. trivialis - S. triangularis lineage characterized by: 1) development of an asymmetric cancellate spinose pore pattern with well-developed coalescing spine collars in S. triangularis. 2) development of wider than high oval-shaped chambers in S. triangularis. 3) increased test size in S. triangularis. Note: the widening of the chambers in S. triangularis causes the umbilicus to open more than in S. trivialis and also lengthens the lip so that it becomes long and narrow.

NONSPINOSE LINEAGES

Praemuricate Lineages Praemurica P. taurica - P. pseudoinconstans - P. inconstans - P. uncinata lineage characterized by: 1) development of a praemuricate cancellate nonspinose wall texture in P. taurica in the transition from Hedbergella monmouthensis. 2) increased number of chambers in the final whorl in in P. taurica. 3) development of subconical-shaped chambers in the transition from P. Inconstans to P. uncinata.

Igorina Praemurica uncinata-Igorina lineage characterized by: 1) development of a thick, encrusted pustule layering over the praemuricate wall in the transition from Praemurica to Igorina. 2) development of slightly conical to elongate oval-shaped chambers in Igorina. 3) development of a somewhat elevated trochospire in Igorina.

I. pusilla - I. laevigata lineage characterized by: 1) low conical chambers in the lineage. 2) development of a peripheral keel in I. laevigata.

I. pusilla - I. tadjikistanensis lineage characterized by: 1) development of inflated ovoid-conical chambers in I. tadjikistanensis.

Smooth-walled Lineage Globanomalina G. archeocompressa - G. compressa - G. ehrenbergi - G. pseudomenardii lineage characterized by: 1) a compressed test with an imperforate peripheral margin which becomes keeled in G. pseudomenardii. 2) increased size and rate of expansion of chambers in the lineage. 3) a change in chamber shape from compressed ovoid in G. archeocompressa-G. ehrenbergi to low conical in G. pseudomenardii.

G. compressa - G. chapmani - G. planoconica lineage characterized by: 1) a compressed, nearly planispiral test with an imperforate peripheral margin that becomes thickened into a blunt keel in G. planoconica. 2) increased size and rate of expansion of chambers in G. chapmani. 3) decreased rate of expansion of chambers, increased number of chambers in the ultimate whorl, and reduced test size in G. planoconica.

G. archeocompressa - G. planocompressa - G. imitata - G. ovalis lineage characterized by: 1) a low trochospiral, nearly planispiral test with rapidly inflating globular chambers in G. planocompressa-G. imitata. 2) a largely perforate peripheral margin in the lineage. 3) a large extraumbilical aperture that extends slightly onto the spiral side in G. ovalis.

G. imitata - G. australiformis lineage characterized by: 1) development of low conical chambers in G. australiformis. 2) development of fine pustules covering the test walls. 3) increased test size in G. australiformis.

Muricate Lineages Acarinina A subtle but significant coiling change, which is first observed in the ancestral species Acarinina strabocella, occurs in the development of Acarinina. In A. strabocella, the coil becomes slightly elevated, thereby shifting the aperture from an umbilical to a slightly extraumbilical position. This evolved character is maintained in all subsequent species of Acarinina.

Morozovella praeangulata - Acarinina strabocella lineage characterized by: 1) development of a muricate wall texture in M. praeangulata. 2) development of oval-elongate chambers in A. strabocella. 3) development of a slightly elevated trochospire in A. strabocella. 4) a more umbilically directed aperture in A. strabocella. Note: The muricate wall is developed by growth of pustules on a smooth surface at triple points between the pores; moderate to strong pustule growth occurs on the umbilical shoulders surrounding the aperture. The elevated trochospire in A. strabocella causes the aperture to take a more umbilical position and tends to close off the umbilicus.

A. strabocella - A. nitida characterized by: 1) development of muricate wall texture. 2) development of a more elongate chamber shape than in A. strabocella.

A. nitida - A. subsphaerica lineage characterized by: 1) development of a higher trochospire and a more tightly coiled test in A. subsphaerica.

A. subsphaerica - A. mckannai characterized by: 1) development of muricate wall texture. 2) oval-elongate chambers which are derived from A. strabocella.

A. mckannai - A. soldadoensis lineage characterized by: 1) a change in chamber shape to less elongate-oval in edge view in A. soldadoensis.

A. nitida - A. coalingensis lineage characterized by: 1) a change to more elongate-oval chambers in spiral view and less elongate-oval chambers in edge view in A. coalingensis. 2) increased rate of chamber size leading to a more tightly coiled test in A. coalingensis.

Morozovella As noted in the introduction, two opposing hypotheses of the phylogeny of the morozovellid lineage remain unresolved. The traditional view, based on the original hypothesis of Bolli (1957a), was adopted by Blow (1979), Toumarkine and Luterbacher (1985), among others. It derives Morozovella through the enhancement of the anguloconical chambers in the ultimate and penultimate whorls of Praemurica uncinata and further peripheral compression of the test, along with the development of a muricate test in Morozovella. Other morphological features shared by the two genera relate to the interpretation of pore shape, development of muricae, umbilical morphology, and apertural morphology. In addition to these criteria, carbon and oxygen isotopic data are interpreted as supporting this phylogenetic hypothesis (Norris, submitted; Berggren and Norris, submitted). The alternate view (Olsson and Hemleben, submitted) emphasizes the development of the characteristic heavy pustulose wall texture of Morozovella from a smooth-walled Globanomalina ancestor, i.e. G. imitata. It is based on the observation that the wall texture of Morozovella develops through the growth of pustules on a smooth wall surface, thus linking this genus to Globanomalina. Anguloconical chambers and a lightly pustulose wall are observed in the inner whorl of G. imitata. In contrast, the Praemurica wall texture develops as elongate subparallel ridges with short connective ridges, giving the wall a cancellate texture similar to the modern species Neogloboquadrina dutertrei. The two phylogenetic hypotheses are shown in Text-figures 5a and b.

Morozovella praeangulata characterized by: 1) development of a pustulose wall surface. 2) development of conical chambers in. 3) maintenance of 5 chambers in ultimate whorl.

M. praeangulata - M. apanthesma - M. aequa - M. subbotinae lineage characterized by: 1) development of high to moderately high conical chambers in the transition to Morozovella from Globanomalina. 2) increased rate of chamber expansion in M. aequa and M. subbotinae.

M. apanthesma - M. gracilis lineage characterized by: 1) development of moderately high conical chambers in M. gracilis. 2) a change to a higher rate of expansion of chambers in M. gracilis.

M. praeangulata - M. angulata - M. conicotruncata - M. velascoensis-pasionensis lineage characterized by: 1) development of high conical chambers in M. conicotruncata. 2) development of a strong muricate keel in M. conicotruncata. 3) development of strongly muricate umbilical shoulders in M. conicotruncata.

M. pasionensis - M. occlusa lineage characterized by: 1) development of low conical chambers in M. occlusa. 2) development of a more tightly coiled test which narrows the umbilicus in M. occlusa.

M. pasionensis - M. acutispira lineage characterized by: 1) development of low conical chambers in M. acutispira. 2) increase rate of chamber expansion in M. acutispira.

Last updated March 4, 1999