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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

The role of eustasy in early late Miocene odobenid diversification in Hokkaido, Japan.
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pone.0131856.g013: The role of eustasy in early late Miocene odobenid diversification in Hokkaido, Japan.

Mentions: Considering the relationships between the sea-level changes and the diversification of the archaic odobenids, the occurrence of a regression phase just before the transgression may have been a driving force for the odobenid speciation during the late Miocene (see Fig 13). Firstly, during the transgression of Sequence 3, a common ancestor of both Pseudotaria muramotoi and Archaeodobenus akamatsui might have occupied a wide range along the western North Pacific coast, tied to availability of shoreline habitat for reproduction. Then, from the end of Sequence 3 to the beginning of Sequence 4 (11.0–10.0 Ma), the sudden sea-level fall resulted in reproductive isolation driven by considerable loss of their shelf habitats.


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

Tanaka Y, Kohno N - PLoS ONE (2015)

The role of eustasy in early late Miocene odobenid diversification in Hokkaido, Japan.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0131856.g013: The role of eustasy in early late Miocene odobenid diversification in Hokkaido, Japan.
Mentions: Considering the relationships between the sea-level changes and the diversification of the archaic odobenids, the occurrence of a regression phase just before the transgression may have been a driving force for the odobenid speciation during the late Miocene (see Fig 13). Firstly, during the transgression of Sequence 3, a common ancestor of both Pseudotaria muramotoi and Archaeodobenus akamatsui might have occupied a wide range along the western North Pacific coast, tied to availability of shoreline habitat for reproduction. Then, from the end of Sequence 3 to the beginning of Sequence 4 (11.0–10.0 Ma), the sudden sea-level fall resulted in reproductive isolation driven by considerable loss of their shelf habitats.

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