An official website of the United States government
The Eocene-Oligocene transition marks a period of dramatic global climatic change correlated with pronounced mammalian faunal change. Fossil evidence is indispensable for studying the distribution of taxa through time, and determining how abiotic parameters shaped ancient biodiversity. Here we report ruminant artiodactyls and a new anthropoid primate from Süngülü, a locality in Eastern Anatolia that has yielded a diversified and largely endemic assemblage of rodents. Three taxa of ruminants are recognized, the tragulid Iberomeryx parvus Gabunia, 1964, a larger species of Iberomeryx Gabunia, 1964, and a bachitheriid referred to cf. Bachitherium sp. A lower molar is identified as the new eosimiid primate Sungulusimias unayae n. gen., n. sp., which is the first occurrence of Paleogene anthropoids in western Asia. The lower molar of Sungulusimias unayae n. gen., n. sp. is characterized by protoconid and metaconid closely spaced and of similar height and volume, paraconid cuspidate and nearly connate with metaconid, strong mesiobuccal cingulid, and entoconid without strong connection to hypoconulid via the postcristid. The composition of this assemblage together with rodents indicates a probable Latest Eocene age for Süngülü, although an early Oligocene age cannot be completely ruled out. The rodent fauna from Süngülü suggests that endemism persisted at the periphery of Balkanatolia until the latest Eocene while Eastern Anatolia was situated in a strategic corridor for faunal exchanges between eastern Asia, Indo-Pakistan and Europe. During the Eocene-Oligocene transition, Balkanatolia probably functioned as a “holding pen” where various taxa were confined for significant intervals of time before proceeding to colonize Western Europe at the Grande Coupure.
more »
« less
Widespread loss of mammalian lineage and dietary diversity in the early Oligocene of Afro-Arabia
Abstract Diverse lines of geological and geochemical evidence indicate that the Eocene-Oligocene transition (EOT) marked the onset of a global cooling phase, rapid growth of the Antarctic ice sheet, and a worldwide drop in sea level. Paleontologists have established that shifts in mammalian community structure in Europe and Asia were broadly coincident with these events, but the potential impact of early Oligocene climate change on the mammalian communities of Afro-Arabia has long been unclear. Here we employ dated phylogenies of multiple endemic Afro-Arabian mammal clades (anomaluroid and hystricognath rodents, anthropoid and strepsirrhine primates, and carnivorous hyaenodonts) to investigate lineage diversification and loss since the early Eocene. These analyses provide evidence for widespread mammalian extinction in the early Oligocene of Afro-Arabia, with almost two-thirds of peak late Eocene diversity lost in these clades by ~30 Ma. Using homology-free dental topographic metrics, we further demonstrate that the loss of Afro-Arabian rodent and primate lineages was associated with a major reduction in molar occlusal topographic disparity, suggesting a correlated loss of dietary diversity. These results raise new questions about the relative importance of global versus local influences in shaping the evolutionary trajectories of Afro-Arabia’s endemic mammals during the Oligocene.
more »
« less
- Award ID(s):
- 2023087
- PAR ID:
- 10304767
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Communications Biology
- Volume:
- 4
- Issue:
- 1
- ISSN:
- 2399-3642
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Although trionychians have a rich fossil record, much of their fossil diversity is known from the Cretaceous and Paleogene, and little is known about their evolutionary history in the Neogene. We here describe cranial and shell material of trionychians from the Early Miocene Moghra Formation of Egypt that we attribute to a new carettochelyid taxon,Allaeochelys meylanisp. nov., and to theTrionyxlineage.Allaeochelys meylanisp. nov. fills a temporal gap between previously described taxa and exhibits a series of unique features, including greatly thickened cranial bones, a broad bony wall posterior to the orbit, a large fossa formed by the maxilla and premaxilla at the anterior third of the triturating surface, and a medial process on peripheral II.Allaeochelys meylanisp. nov. also documents the oldest occurrence ofCarettochelyidaeon the Afro-Arabian continent, while theTrionyxmaterial reported herein provides unambiguous evidence for the presence of this lineage on the Afro-Arabian continent no later than the Early Miocene.more » « less
-
ABSTRACT AimWe assess the systematic relationships and historical biogeographic patterns in the subfamily Scincinae, a group of lizards that primarily inhabits the Afro‐Madagascan and Saharo‐Arabian regions with isolated lineages in Europe, North America, East Asia, India and Sri Lanka. The contemporary distribution of these lineages on the historical Laurasian and Gondwanan landmasses make scincines an ideal system to study the roles of vicariance and dispersal on a geologic scale of tens of millions of years. LocationGlobal. TaxonSubfamily Scincinae (Family Scincidae). MethodsWe conducted biogeographic analyses on a reconstructed, time‐calibrated species tree of scincine genera, including members of the other Scincidae subfamilies, using seven nuclear loci (~6 k base pairs). We also constructed a lineage‐through‐time plot to assess the timing of diversification within scincines. ResultsOur analysis estimated strong support for the monophyly of Scincinae that is further comprised a strongly‐supported Gondwanan clade nested within a broader Laurasian group. While most of the extant, genus‐level diversity within the Gondwanan clade was accrued post‐Eocene, the majority of the Laurasian lineages diverged during the Palaeocene or earlier, suggesting large‐scale extinctions on continents of Laurasian origin. Counterintuitively, scincines from India and Sri Lanka have distinct biogeographical origins despite a long tectonic association between these landmasses, suggesting at least two independent, long‐distance, trans‐oceanic dispersal events into the subcontinent. Our biogeographic analyses suggest that scincines likely originated in East and Southeast Asia during the late Cretaceous (ca. 70 Ma), and eventually dispersed westwards to Africa and Madagascar, where their greatest current‐day species richness occurs. Main ConclusionsOur study demonstrates the concomitant roles of dispersal and extinction in shaping modern‐day assemblages of ancient clades such as scincine lizards. Our range evolution analysis shows that despite the greater diversity observed in the Afro‐Madagascan region, the origin of scincines can be traced back to Southeast Asia and East Asia, followed by westward dispersals. These dispersals may have been followed by significant extinctions in tropical East Asia, resulting in relatively lower diversity of scincines in these regions. Notably, our analysis reveals that Sri Lankan and Peninsular Indian scincines have distinct evolutionary origins.more » « less
-
Abstract The Eocene-Oligocene Transition atc.34 million years ago (Ma) marked the global change from greenhouse to icehouse and the establishment of the East Antarctic Ice Sheet (EAIS). How the ice-sheet behaviour changed during interglacials across this climate transition is poorly understood. We analysed major, trace and rare earth elemental data of late Eocene interglacial mudstone from Prydz Bay at Ocean Drilling Program Site 1166 and early Oligocene interglacial mudstone from Integrated Ocean Drilling Program Site U1360 on the Wilkes Land continental shelf. Both sites have comparable glaciomarine depositional settings. Lithofacies and provenance at Site 1166 in Prydz Bay are indicative of a late Eocene glacial retreat in the Lambert Graben. Palaeoclimate proxies, including the Chemical Index of Alteration, mean annual temperature and mean annual precipitation, show a dominant warm and humid palaeoclimate for the late Eocene interglacial. In contrast, at Site U1360, in the early Oligocene, the provenance and interglacial weathering regime remained relatively stable with conditions of physical weathering. These results confirm that the EAIS substantially retreated periodically during late Eocene interglacials and that subglacial basins probably remained partially glaciated during interglacials in the earliest Oligocene.more » « less
-
During International Ocean Discovery Program Expeditions 390C, 395E, 390, and 393 (the South Atlantic Transect), seven sites were drilled on the western flank of the southern Mid-Atlantic Ridge. Among these sites, Sites U1557 and U1558 recovered Eocene and Oligocene sediments. Such sediments will allow a better understanding of how ocean ecosystems, as well as ocean circulation and chemistry, responded to the paleoceanographic and paleoclimatic changes leading to the Eocene–Oligocene transition. In this study, we present early Eocene through early Oligocene carbon and oxygen stable isotope data (δ13C and δ18O) of bulk carbonates from sediment samples collected in Holes U1557B, U1558A, and U1558F. The data show that the western South Atlantic, a relatively understudied region for the Eocene, recorded some global geochemical features, such as the relatively low δ13C and δ18O values typical of hyperthermal events characterizing the onset of the Early Eocene Climatic Optimum and the rapid shift toward high δ18O and δ13C values at the Eocene/Oligocene boundary.more » « less
