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Wyświetlanie 1-2 z 2
Tytuł:
Multispecies leatherback turtle assemblage from the Oligocene Chandler Bridge and Ashley formations of South Carolina, USA
Autorzy:
Fallon, B.R.
Boessenecker, R.W.
Powiązania:
https://bibliotekanauki.pl/articles/2082243.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Chelonioidea
Natemys
Egyptemys
Psephophorus
Paleogene
Oligocene
North America
Opis:
Paleogene dermochelyid species richness far exceeded that of today. Leatherback sea turtles were most species rich in the Paleogene, but their richness declined sharply during the Neogene with only one species existing today, Dermochelys coriacea. We describe the fossil remains of three leatherback genera (Natemys, Psephophorus, and Egyptemys) from the upper Oligocene Chandler Bridge Formation and two (Natemys and Psephophorus) from the lower Oligocene Ashley Formation of South Carolina, USA. The fossils consist of isolated and some associated carapacial ossicles. Several ossicles are referred to Natemys sp. because their scalloped edges are indicative of the carapacial sunflower pattern specific to this genus. Additionally, two Natemys morphotypes (Natemys sp. 1 and 2) are distinguished based on differences in ossicle thickness and internal structure. We refer two ossicles to cf. Psephophorus sp. because of their internal diploic structure and because one has a dorsal radial pattern while the other has a prominent ridge that exhibits strong visceral concavity. Finally, we refer one ossicle to cf. Egyptemys sp. because it has a shallow keel that shows little expression on the visceral surface, although we also acknowledge the ossicle’s similarity to some ridged ossicles of the genus Psephophorus. These ossicles represent the first multispecies assemblage of leatherback fossils reported worldwide. Furthermore, the specimens fill both temporal and geographic gaps for extinct leatherback genera and represent the first formally described dermochelyids from South Carolina and the Oligocene of the Atlantic Coastal Plain.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 4; 763-776
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Youngest record of the extinct walrus Ontocetus emmonsi from the Early Pleistocene of South Carolina and a review of North Atlantic walrus biochronology
Autorzy:
Boessenecker, S.J.
Boessenecker, R.W.
Geisler, J.H.
Powiązania:
https://bibliotekanauki.pl/articles/20111.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
The extinct North Atlantic walrus Ontocetus emmonsi is widely reported from Pliocene marine deposits in the eastern USA (New Jersey, Florida), Belgium, Netherlands, Great Britain, and Morocco. Ontocetus was slightly larger than the modern walrus Odobenus rosmarus, may have had wider climatic tolerances (subtropical), and likely originated in the western North Pacific before dispersing through the Arctic. Owing to geochronologic uncertainties in the North Atlantic Plio-Pleistocene walrus record, it is unclear whether Ontocetus and Odobenus overlapped in time and thus may have competed, or whether the two were temporally separate invasions of the North Atlantic. A new specimen of Ontocetus emmonsi (CCNHM-1144) from the Austin Sand Pit (Ridgeville, South Carolina, USA) is a complete, well-preserved left tusk that is proximally inflated and oval in cross-section, relatively short (maximum length: 369 mm) and markedly curved (radius of arc of curvature 197 mm). Globular dentine is present, confirming assignment to Odobenini; proportions and curvature identify the specimen as Ontocetus emmonsi rather than Odobenus. Hitherto unstudied deposits in the Austin Sand Pit lack calcareous macro and microinvertebrates, but vertebrate biochronology provides some temporal resolution. The co-occurrence of a giant beaver (Castoroides sp.) and a snaggletooth shark (Hemipristis serra) indicate an age of 1.1–1.8 Ma (Early Pleistocene) and correlation with the Lower Pleistocene Waccamaw Formation. The vertebrate assemblage is named the Ridgeville Local Fauna. The composition of the marine mammal assemblage from the Austin Sand Pit is intermediate between that of the lower Pliocene Yorktown Formation (North Carolina, USA) and the modern North Atlantic fauna. This record reported here is the youngest of Ontocetus emmonsi from the Atlantic Coastal Plain. A review of North Atlantic Plio-Pleistocene walrus records reveals no overlap between extinct Ontocetus and extant Odobenus—suggesting independent dispersal to the North Atlantic and a lack of competition.
Źródło:
Acta Palaeontologica Polonica; 2018, 63, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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