نتایج جستجو برای: eocene
تعداد نتایج: 4349 فیلتر نتایج به سال:
The Jebel Qatrani Formation of northern Egypt has produced Afro-Arabia's primary record of Paleogene mammalian evolution, including the world's most complete remains of early anthropoid primates. Recent studies of Fayum mammals have assumed that the Jebel Qatrani Formation contains a significant Eocene component ( approximately 150 of 340 m), and that most taxa from that succession are between ...
We report the oldest known record of Lagomorpha, based on distinctive, small ankle bones (calcaneus and talus) from Early Eocene deposits (Middle Ypresian equivalent, ca 53 Myr ago) of Gujarat, west-central India. The fossils predate the oldest previously known crown lagomorphs by several million years and extend the record of lagomorphs on the Indian subcontinent by 35 Myr. The bones show a mo...
Today coral reefs are threatened by changes to seawater conditions associated with rapid anthropogenic global climate change. Yet, since the Cenozoic, these organisms have experienced major fluctuations in atmospheric CO2 levels (from greenhouse conditions of high pCO2 in the Eocene to low pCO2 ice-house conditions in the Oligocene-Miocene) and a dramatically changing ocean Mg/Ca ratio. Here we...
The Paleocene-Eocene transition in North American land-mammal faunas is well documented on the south side of Polecat Bench and in surrounding badlands of northwestern Wyoming. Here a rich fossil record is known from a stratigraphic section with an established geomagnetic polarity time scale and mediumto high-resolution carbon and oxygen isotope records. The Paleocene-Eocene carbon isotope excur...
Biometric analysis of the teeth of fossil and Recent hexanchid sharks and its taxonomic implications
A biometric analysis of the lower teeth of Recent cow sharks (Hexanchidae) investigates the ontogenetic and phylogen− etic aspects of the dental characters employed by many ichthyologists and palaeontologists. The dental characters cur− rently used to separate two extant species of sixgill sharks (Hexanchus griseus and H. nakamurai) are analysed and the fossil record of their relatives reviewed...
[1] The dynamic subsidence of the United States east coast is addressed using the discrepancy between regional and global estimates of sea level, elevation of paleoshorelines, and adjoint models of mantle convection that assimilate plate motions and seismic tomography. The positions of Eocene and Miocene paleoshorelines are lower than predicted by global sea levels, suggesting at least 50 m, an...
BACKGROUND The Saururaceae, a very small family of Piperales comprising only six species in four genera, have a relatively scanty fossil record outside of Europe. The phylogenetic relationships of the four genera to each other are resolved, with the type genus Saururus occurring in both eastern North America and East Asia. No extant species occurs in western Eurasia. The most exceptional find s...
Primates appear at or immediately after the beginning of the Eocene, in the global carbon isotope excursion (CIE) marking the Paleocene–Eocene Thermal Maximum. We presented evidence for dispersal of Teilhardina from Asia to Europe to North America in the first 25 kyr of the CIE (first 25 kyr of the Eocene; ref. 1). Beard claims to refute the direction of dispersal by reporting a new, possibly o...
The geographic origin of bats is still unknown, and fossils of earliest bats are rare and poorly diversified, with, maybe, the exception of Europe. The earliest bats are recorded from the Early Eocene of North America, Europe, North Africa and Australia where they seem to appear suddenly and simultaneously. Until now, the oldest record in Asia was from theMiddle Eocene. In this paper, we report...
A frequently cited atmospheric CO2 threshold for the onset of Antarctic glaciation of ∼ 780 ppmv is based on the study of DeConto and Pollard (2003) using an ice sheet model and the GENESIS climate model. Proxy records suggest that atmospheric CO2 concentrations passed through this threshold across the Eocene–Oligocene transition ∼ 34 Ma. However, atmospheric CO2 concentrations may have been cl...
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