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Expanding the geographic and geochronologic range of early pinnipeds: New specimens of Enaliarctos from Northern California and Oregon

100%

Poust A. W., Boessenecker R. W.

Acta Palaeontologica Polonica

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2018

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tom 63

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nr 1

The early pinnipedimorph Enaliarctos was a marine-adapted carnivore with dental and locomotor features intermediate between terrestrial arctoids and living pinnipeds. New specimens of Enaliarctos are described from Oligocene and Miocene deposits on the Pacific coast of North America, and include the oldest enaliarctine mandible (Yaquina Formation, 30.6–27.4 Ma), the first enaliarctine from Northern California (Skooner Gulch Formation, 23.8–22 Ma), and the stratigraphically youngest fossil of the genus (Astoria Formation, 17.3–16.6 Ma). The wide biogeographic and temporal range of Enaliarctos provided the potential for interaction or competition with plotopterid birds, odontocete whales, and crown pinnipeds such as early odobenids, early otariids, and desmatophocids. The expansion of the known ranges of Enaliarctos species and the description of additional morphology, particularly of the mandible and lower dentition, provides insight into the origins of pinniped diversity and their possible interactions with other early Neogene coastal marine organisms.

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Multispecies leatherback turtle assemblage from the Oligocene Chandler Bridge and Ashley formations of South Carolina, USA

100%

Fallon B. R., Boessenecker R. W.

Acta Palaeontologica Polonica

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2020

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tom 65

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nr 4

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Youngest record of the extinct walrus Ontocetus emmonsi from the Early Pleistocene of South Carolina and a review of North Atlantic walrus biochronology

81%

Boessenecker S. J., Boessenecker R. W., Geisler J. H.

Acta Palaeontologica Polonica

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2018

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tom 63

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nr 2

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.

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Globicephaline whales from the Mio-Pliocene Purisima Formation of central California, USA

81%

Boessenecker R. W., Perry F. A., Geisler J. H.

Acta Palaeontologica Polonica

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2015

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tom 60

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nr 1

Oceanic dolphins (Odontoceti: Delphinidae) constitute the most speciose family of extant cetaceans, yet their fossil record is limited. Although several extinct species are known from Mediterranean and North Atlantic localities, there are few examples from deposits along the Pacific Rim. Despite the rich record of successive marine mammal fossil assemblages in the extensively sampled eastern North Pacific, only one fossil delphinid, Protoglobicephala (Pliocene, Baja California), has been described. We report globicephaline remains from the Mio-Pliocene Purisima Formation of Northern California, including a partial cranium and two isolated petrosals. The skull exhibits large ridges on the premaxillae, and cannot be referred to any extant globicephaline genus. Similarly, the petrosals cannot be referred to any described delphinid genus, although they are most similar to those of Globicephala. Linear regression analyses demonstrate that promontorium length and bony nares width scale significantly within delphinidans, and provide a new method for testing referrals of isolated fossil odontocete petrosals to taxa known only by crania. Applying this method to the new globicephalines from the Purisima Formation, we find the petrosals to be too small to represent the same taxon as the skull, thus indicating the presence of two separate species. Our results demonstrate that globicephalines had achieved a worldwide distribution by the early Pliocene, suggesting diversification of the subfamily by 5 Ma.

Ograniczanie wyników

4 Acta Palaeontologica Polonica

4 Boessenecker R. W.

2 Geisler J. H.

1 Boessenecker S. J.

1 Fallon B. R.

1 Perry F. A.

1 Poust A. W.

1 2020

2 2018

1 2015

Expanding the geographic and geochronologic range of early pinnipeds: New specimens of Enaliarctos from Northern California and Oregon

Multispecies leatherback turtle assemblage from the Oligocene Chandler Bridge and Ashley formations of South Carolina, USA

Youngest record of the extinct walrus Ontocetus emmonsi from the Early Pleistocene of South Carolina and a review of North Atlantic walrus biochronology

Globicephaline whales from the Mio-Pliocene Purisima Formation of central California, USA