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A New Late Miocene Odobenid (Mammalia: Carnivora) from Hokkaido, Japan Suggests Rapid Diversification of Basal Miocene Odobenids.

Tanaka Y, Kohno N - PLoS ONE (2015)

Bottom Line: A new genus and species of archaic odobenid, Archaeodobenus akamatsui, gen. et sp. nov. from the late Miocene (ca. 10.0-9.5 Ma) top of the Ichibangawa Formation, Hokkaido, northern Japan, suggests rapid diversification of basal Miocene walruses.Archaeodobenus akamatsui is the contemporaneous Pseudotaria muramotoi from the same formation, but they are distinguishable from each other in size and shape of the occipital condyle, foramen magnum and mastoid process of the cranium, and other postcranial features.Based on our phylogenetic analysis, A. akamatsui might have split from P. muramotoi at the late Miocene in the western North Pacific.

View Article: PubMed Central - PubMed

Affiliation: Hokkaido University Museum, Kita 8 Nishi 5, Kita-ku, Sapporo, Hokkaido, 060-0808, Japan; Department of Geology, University of Otago, 360 Leith walk, PO Box 56, Dunedin, 9054, New Zealand; Numata Fossil Museum, 2-7-49, 1 Minami, Numata Town, Hokkaido, 078-2202, Japan.

ABSTRACT
The modern walrus, Odobenus rosmarus, is specialized and only extant member of the family Odobenidae. They were much more diversified in the past, and at least 16 genera and 20 species of fossil walruses have been known. Although their diversity increased in the late Miocene and Pliocene (around 8-2 Million years ago), older records are poorly known. A new genus and species of archaic odobenid, Archaeodobenus akamatsui, gen. et sp. nov. from the late Miocene (ca. 10.0-9.5 Ma) top of the Ichibangawa Formation, Hokkaido, northern Japan, suggests rapid diversification of basal Miocene walruses. Archaeodobenus akamatsui is the contemporaneous Pseudotaria muramotoi from the same formation, but they are distinguishable from each other in size and shape of the occipital condyle, foramen magnum and mastoid process of the cranium, and other postcranial features. Based on our phylogenetic analysis, A. akamatsui might have split from P. muramotoi at the late Miocene in the western North Pacific. This rapid diversification of the archaic odobenids occurred with a combination of marine regression and transgression, which provided geological isolation among the common ancestors of extinct odobenids.

No MeSH data available.


Related in: MedlinePlus

Locality map and stratigraphic sections of the Archaeodobenus akamatsui holotype locality, based on Takano et al. (1996).
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pone.0131856.g002: Locality map and stratigraphic sections of the Archaeodobenus akamatsui holotype locality, based on Takano et al. (1996).

Mentions: A partial skeleton of a fossil pinniped was collected from the late Miocene Ichibangawa Formation in Tobetsu Town, Hokkaido, Japan (Figs 1 and 2). This skeleton includes a partial cranium, mandibles, anterior vertebrae and some appendicular bones. Previously, the holotype and paratype of the extinct odobenid, Pseudotaria muramotoi Kohno, 2006, were collected from the same formation in the same locality area. The new fossil has similar character combinations to those in P. muramotoi, suggesting that it also belongs to the family Odobenidae. However, the third specimen has some unique characters differentiation it from the previously known specimens of P. muramotoi from the same locality area and also other species in the Odobenidae. In the present paper, we describe the new fossil as a new genus and species of the family Odobenidae and examine its phylogenetic relationships among them to provide additional information and understand the evolutionary diversification of the odobenids during the Miocene.


A New Late Miocene Odobenid (Mammalia: Carnivora) from Hokkaido, Japan Suggests Rapid Diversification of Basal Miocene Odobenids.

Tanaka Y, Kohno N - PLoS ONE (2015)

Locality map and stratigraphic sections of the Archaeodobenus akamatsui holotype locality, based on Takano et al. (1996).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526471&req=5

pone.0131856.g002: Locality map and stratigraphic sections of the Archaeodobenus akamatsui holotype locality, based on Takano et al. (1996).
Mentions: A partial skeleton of a fossil pinniped was collected from the late Miocene Ichibangawa Formation in Tobetsu Town, Hokkaido, Japan (Figs 1 and 2). This skeleton includes a partial cranium, mandibles, anterior vertebrae and some appendicular bones. Previously, the holotype and paratype of the extinct odobenid, Pseudotaria muramotoi Kohno, 2006, were collected from the same formation in the same locality area. The new fossil has similar character combinations to those in P. muramotoi, suggesting that it also belongs to the family Odobenidae. However, the third specimen has some unique characters differentiation it from the previously known specimens of P. muramotoi from the same locality area and also other species in the Odobenidae. In the present paper, we describe the new fossil as a new genus and species of the family Odobenidae and examine its phylogenetic relationships among them to provide additional information and understand the evolutionary diversification of the odobenids during the Miocene.

Bottom Line: A new genus and species of archaic odobenid, Archaeodobenus akamatsui, gen. et sp. nov. from the late Miocene (ca. 10.0-9.5 Ma) top of the Ichibangawa Formation, Hokkaido, northern Japan, suggests rapid diversification of basal Miocene walruses.Archaeodobenus akamatsui is the contemporaneous Pseudotaria muramotoi from the same formation, but they are distinguishable from each other in size and shape of the occipital condyle, foramen magnum and mastoid process of the cranium, and other postcranial features.Based on our phylogenetic analysis, A. akamatsui might have split from P. muramotoi at the late Miocene in the western North Pacific.

View Article: PubMed Central - PubMed

Affiliation: Hokkaido University Museum, Kita 8 Nishi 5, Kita-ku, Sapporo, Hokkaido, 060-0808, Japan; Department of Geology, University of Otago, 360 Leith walk, PO Box 56, Dunedin, 9054, New Zealand; Numata Fossil Museum, 2-7-49, 1 Minami, Numata Town, Hokkaido, 078-2202, Japan.

ABSTRACT
The modern walrus, Odobenus rosmarus, is specialized and only extant member of the family Odobenidae. They were much more diversified in the past, and at least 16 genera and 20 species of fossil walruses have been known. Although their diversity increased in the late Miocene and Pliocene (around 8-2 Million years ago), older records are poorly known. A new genus and species of archaic odobenid, Archaeodobenus akamatsui, gen. et sp. nov. from the late Miocene (ca. 10.0-9.5 Ma) top of the Ichibangawa Formation, Hokkaido, northern Japan, suggests rapid diversification of basal Miocene walruses. Archaeodobenus akamatsui is the contemporaneous Pseudotaria muramotoi from the same formation, but they are distinguishable from each other in size and shape of the occipital condyle, foramen magnum and mastoid process of the cranium, and other postcranial features. Based on our phylogenetic analysis, A. akamatsui might have split from P. muramotoi at the late Miocene in the western North Pacific. This rapid diversification of the archaic odobenids occurred with a combination of marine regression and transgression, which provided geological isolation among the common ancestors of extinct odobenids.

No MeSH data available.


Related in: MedlinePlus