Middle Eocene habitat shifts in the North American western interior: A case study

There has been great interest in the global warming events that heralded the onset of the Eocene and particularly the response of mammalian faunas to these events. However, little information is available on the subsequent deterioration of tropical habitats in the interior of North America after these major warming episodes. The decline of tropical habitats is thought to have begun during the middle Eocene in the interior of North America, but until now, no studies have been able to document the details of this event. Recent fossil collection and stratigraphic studies from sites in southwestern Wyoming and northeastern Utah that span the middle Eocene offer a unique opportunity to evaluate changes in habitat in the western interior. Using a discriminant function analysis, habitats were reconstructed for a sequence of eight stratigraphically controlled middle Eocene assemblages. Adaptive profiles (diets, substrate use, and body masses) of fossil mammal communities were statistically compared to those of extant faunas from a variety of Neotropical habitats. Previously published magnetostratigraphic data from Utah provided a means to correlate our stratigraphic sections to the geomagnetic polarity time scale and the oxygen isotope record. The discriminant model shows that there was a significant change in the mammalian community ecology near the end of the late middle Eocene that is likely reflective of a habitat shift. When correlated to the time scale and oxygen isotope record, this key transition from forested habitats typical of the tropical early Eocene to more open woodlands began about 42 million years ago in this region of the Rocky Mountains.     

内蒙古苏崩地点的古新世软食中兽(哺乳纲,中兽目):古新世-始新世界线附近“东方伊甸园”扩散模式的新证据(英文)

记述了发现于内蒙古苏崩晚古新世格沙头期的中兽类软食中兽Hapalodectes属的一个新种。这是软食中兽在中国古新世地层中的首次发现,也是亚洲格沙头期的第二种软食中兽。已有的系统学和生物地层学证据支持软食中兽属和软食中兽科(Hapalodectidae)亚洲起源的观点。软食中兽显然是在古新世-始新世极热事件(PETM)期间通过白令陆桥扩散到北美大陆的,因而符合"东方伊甸园"学说中的生物地理格局。软食中兽有限的(即非欧洲的)地理分布使得我们可以重建该属生物地理学历史。如同软食中兽一样的"东方伊甸园"式的扩散模式,可以看作是大的环境变化事件导致多个支系产生相似的系统学和生物地理学分布格局的生物地理扩散机制。严格地检查了所谓的在古新世-始新世界线上或其附近的与"东方伊甸园"模式相矛盾的大陆间哺乳动物扩散事例,结果发现这些例子都是不可靠的。"东方伊甸园"生物地理学说充分解释了PETM时期哺乳动物群更替以及劳亚古陆哺乳动物地理分布格局的成因。     

Reassessment of the Early–Middle Eocene biomagnetochronology based on evidence from the Gorrondatxe section (Basque Country, western Pyrenees)

Thirteen Lower–Middle Eocene (Ypresian–Lutetian) successions, including the Gorrondatxe section in the western Pyrenees, show biomagnetostratigraphic correlation schemes that do not agree with the current standard framework. The main discrepancy concerns the position of the boundary between planktonic foraminiferal Zones P9 (=E7, approximately) and P10 (=E8, approximately), which was thought to occur within calcareous nannofossil Subzone CP12a and at the boundary between magnetic polarity Chrons C22n and C21r. However, in the differing correlation scheme the boundary between Zones P9 (=E7) and P10 (=E8) occurs close to the base of Subzone CP13a and to the boundary between Chrons C21n and C20r. An attempt at a new Ypresian–Lutetian boundary biomagnetochronology is made based on data from the Gorrondatxe section, which shows that the boundary between Zones P9 (=E7) and P10 (=E8) is 3.1 Myr younger than hitherto considered. Therefore, the duration of the Early Eocene, most commonly defined according to this planktonic foraminiferal zonal boundary, has generally been underestimated over the last four decades.     

Wasatchian (Early Eocene) pollen floras from the Red Hot Truck Stop, Mississippi, USA

Sediments at the Red Hot Truck Stop (RHTS), Mississippi, USA are important because they contain the lowest latitude record of both the earliest known Eocene plant and mammal fossils in North America. The RHTS contains the uppermost Tuscahoma Formation and the lowermost part of the basal Bashi and Hatchetigbee formations. The Tuscahoma Formation is composed of glauconitic sands and silts that represent estuarine to shallow marine sediments. Faunal remains indicate that the RHTS section belongs to the Wasatchian North American land mammal age and specifically to the lower Graybullian subdivision. Pollen and spore floras from the RHTS are moderately diverse (113 taxa) and contain families that today are associated with warm‐adapted vegetation types such as Annonaceae, Bombacaceae, Burseraceae and palms. Eocene first occurrences are represented by Brosipollis sp., Celtispollenites sp., Interpollis microsupplingensis, cf. Nuxpollenites psilatus, Platycarya spp., Retistephanocolporites sp. and Symplocos? contracta and by one genus of pteridophyte spore (Granulatisporites sp.). The overall composition and within‐sample diversity of the sporomorph flora is more similar to the Hatchetigbee Formation (early Eocene) than to the middle Tuscahoma Formation (late Palaeocene) but among‐sample diversity remains unchanged across the Palaeocene/Eocene boundary. The distinct composition of the RHTS demonstrates that floral change across the Palaeocene/Eocene boundary is complex and composed of several phases of floral change.     

NEW GENUS OF DORUDONTINE ARCHAEOCETE (CETACEA) FROM THE MIDDLE-TO-LATE EOCENE OF SOUTH CAROLINA

A new archaeocete whale from the late middle or early late Eocene of South Carolina, Chrysocetus healyorum gen. et sp. nov., is described on the basis of a single subadult specimen. This individual includes: a partial skull; hyoid apparatus; lower jaws; teeth; all cervical, some thoracic and some lumbar vertebrae; ribs and sternum; left forelimb elements; and pelves. The specimen includes portions of much of the body, but while some of the bones are fairly complete, others are damaged, particularly the skull. The pelves resemble those of Basilosaurus , documenting a similar stage of hind limb reduction in dorudontines and suggesting that Chrysocetus was not able to support its body on land. The acetabulum for articulation of the femur is well formed and indicates that the hip joint was functional. Chrysocetus is distinguishable from other described dorudontines based on body size, characteristics of the teeth, and forelimb elements. Absence of deciduous teeth in a subadult individual of Chrysocetus may be indicative of an early stage of the evolution of monophyodonty.     

A NEW SPECIES OF MOERITHERIUM (PROBOSCIDEA, MAMMALIA) FROM THE EOCENE OF ALGERIA: NEW PERSPECTIVES ON THE ANCESTRAL MORPHOTYPE OF THE GENUS

Abstract:  A new species of Moeritherium (Proboscidea, Mammalia), M. chehbeurameuri sp. nov., is described from remains discovered in the early late Eocene locality of Bir El Ater, Algeria. Although mainly represented by isolated teeth, it shows distinct synapomorphies which justify its attribution to the genus Moeritherium , together with exclusive features that led to the creation of the new species. The main characteristic of this new taxon is the almost complete lophodonty shown by its molars, while Moeritherium is commonly regarded as a bunolophodont to bunodont taxon. In addition to this lophodonty, this new taxon shows anatomical features as yet unknown for the genus, but often met within lophodont early proboscidean taxa such as Phosphatherium escuilliei and Numidotherium koholense . Although a revision of the whole genus Moeritherium is outside the scope of this paper, the main controversies and discussion about the definition of species within the genus Moeritherium are discussed. The surprising lophodonty of M. chehbeurameuri , together with its small size, its early late Eocene age and the weak molarization of its P₃ support the hypothesis of a lophodont hypothetical ancestor for moeritheres, and therefore strengthen the growing hypothesis of a lophodont dental ancestral morphotype for proboscideans.     

Middle Eocene Ostracods from southeast Fayoum area,Egypt: Systematics,paleobathymetry and paleobiogeography

This study deals with the Middle Eocene ostracods from southeast Fayoum area, Egypt. To carry out this investigation, three outcrops are examined, Gebel Elwe El Breig, Gebel Sath El Hadid and Gebel Munqar El-Shinnara. This study is based on the Midawara Formation that consists mainly of fossiliferous limestone, marly limestone and clay. The studied ostracod assemblage includes thirty-one species and subspecies, belonging to twenty-three genera and seventeen families. The ostracod group belonging to Cytheroidea Baird, 1850 represents the most abundant group that reaches 81.99% in Munqar El-Shinnara section, 81.88% in Sath El Hadid section, and 61.12% in Elwe El Breig section. The structure of the investigated assemblages (abundance of ostracods, number of taxa, Fisher's alpha, Shannon index, and equitability) indicates deposition in an environment belonging to the neritic zone. Moreover, this study tries to use the multivariate analyses to distinguish the paleobiogeographic provinces in Tethyan region during the Middle Eocene. These analyses are applied on a matrix consists of some nominated Middle Eocene species from 13 countries. The results point to two distinctive provinces, Southern Tethys Province (Algeria, Tunisia, Libya, Egypt and Jordan) and the Northern Tethys Province (England, Germany, Spain, France, Belgium, Ukraine, Hungary and Turkey). The reasonable similarities between these provinces may reflect a possible connection between both sides of the Tethys during the Middle Eocene age.     

A whole new world of ancestors: Eocene anthropoideans from Africa

The last decade has witnessed enormous gains in our knowledge of early anthro-poidean primates,

1 “Anthropoidean” refers to members of the suborder Anthropoidea, whch contaings New and Old world monkeys, apes, and humans. These primates are also often called “simians,” “simiiforms” or “anthropoids;” the latter term is potentially confusing because it has often been used to refer only to the great apes.

the oldest known relatives of monkeys, apes and humans. Recent fossil finds in Egypt, Algeria, Tunisia, and Oman, along with the associated geological research at these sites, have radically changed our models of anthro-poidean origins and differentiation. Instead of first appearing as robust-jawed herbivorous primates in the earliest Oligocene, it is now apparent that there was radiation of small-bodied, fruit-and-insect-eating anthropoideans during the Eocene. These early forms included at least two oligopithecines (squirrel-monkey-sized primates with a catarrhine dental formula) and two early “parapithecid monkeys” (three-premolared primates with lumpy, bunodont dentitions). In addition, several smaller species from Algeria and Egypt, ranging in size from pygmy marmosets to tamarins, are not definitely assignable to previously known families. Alongside the early anthropoideans, there are also at least four recently identified prosimian families. The continental Eocene of Africa—for years, little more than a blank on the paieontologi-cal map—now comprises an increasingly productive field source of new data that is important in deciphering phyletic and adaptive aspects of the prosimian-anthropoid transition.     

La faune malacologique des calcaires éocènes de la région de Sabarat (Pyrénées ariégeoises)

Limestone beds included in the «Poudingue dePalassou around Sabarat (Ariège) contain a Gasteropod fauna known since J.-B. Noulet's works (1857). The systematic inventory of the different localities and the paleontological study of the material collected prove that two successive and clearly different Mollusc faunas existed. The bartonian fauna with Ischurostoma formosum minutum (Noulet) and Biomphalaria vasseuri (Roman) is preceded by a lower lutetian fauna with Biomphalaria pseudoammonius (Scholtheim): in the latter, two paleoecological groups are opposed according to the sheltered channels of two kinds in which limestones beds have been built. Besides, the chronostratigraphic consequences imply that the middle part of the «Poudingue de Palassou has been formed from Lower Lutetian to Bartonian.