scholarly journals The oldest record of the Steller sea lion Eumetopias jubatus (Schreber, 1776) from the early Pleistocene of the North Pacific

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9709
Author(s):  
Nahoko Tsuzuku ◽  
Naoki Kohno
Keyword(s):  
North Pacific ◽  
Japan Sea ◽  
Early Pleistocene ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
Sea Lions ◽  
The North ◽  
Fur Seals ◽  
The North Pacific

The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are thought to have emerged in the Pliocene or the early Pleistocene in the North Pacific. Among them, the Steller sea lion (Eumetopias jubatus) is the largest and distributed both in the western and eastern North Pacific. In contrast to the limited distribution of the current population around the Japanese Islands that is now only along the coast of Hokkaido, their fossil records have been known from the middle and late Pleistocene of Honshu Island. One such important fossil specimen has been recorded from the upper lower Pleistocene Omma Formation (ca. 1.36–0.83 Ma) in Kanazawa, Ishikawa Prefecture, Japan, which now bears the institutional number GKZ-N 00001. Because GKZ-N 00001 is the earliest fossil having been identified as a species of the sea lion genus Eumetopias, it is of importance to elucidate the evolutionary history of that genus. The morphometric comparisons were made among 51 mandibles of fur seals and sea lions with GKZ-N 00001. As results of bivariate analyses and PCA based on 39 measurements for external morphologies with internal structures by CT scan data, there is almost no difference between GKZ-N 00001 and extant male individuals of E. jubatus. In this regard, GKZ-N 00001 is identified specifically as the Steller sea lion E. jubatus. Consequently, it is recognized as the oldest Steller sea lion in the North Pacific. About 0.8 Ma, the distribution of the Steller sea lion had been already established at least in the Japan Sea side of the western North Pacific.

Pricetrema phocae and Pricetrema eumetopii spp.n. (Trematoda: Heterophyidae) from pinnipeds in the North Pacific

1978 ◽  
Vol 56 (3) ◽  
pp. 382-385
Author(s):  
Larry M. Shults
Keyword(s):  
North Pacific ◽  
Harbor Seal ◽  
Phoca Vitulina ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
The North ◽  
Phoca Vitulina Richardsi ◽  
The North Pacific

Pricetrema phocae and Pricetrema eumetopii spp.n. are described from the harbor seal, Phoca vitulina richardsi (Gray), and Steller sea lion, Eumetopias jubatus (Schreber), respectively.

The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses

2018 ◽  
Vol 46 (1) ◽  
pp. 203-228 ◽  
Author(s):  
Annalisa Berta ◽  
Morgan Churchill ◽  
Robert W. Boessenecker
Keyword(s):  
North Pacific ◽  
Evolutionary Biology ◽  
Breeding Systems ◽  
Feeding Strategies ◽  
Crown Group ◽  
Sea Lions ◽  
The North ◽  
Fur Seals ◽  
Body Sizes ◽  
The North Pacific

The oldest definitive pinniped fossils date from approximately 30.6–23 million years ago (Ma) in the North Pacific. Pinniped monophyly is consistently supported; the group shares a common ancestry with arctoid carnivorans, either ursids or musteloids. Crown pinnipeds comprise the Otariidae (fur seals and sea lions), Odobenidae (walruses), and Phocidae (seals), with paraphyletic “enaliarctines” falling outside the crown group. The position of extinct Desmatophocidae is debated; they are considered to be closely related to both otariids and odobenids or, alternatively, to phocids. Both otariids and odobenids are known from the North Pacific, diverging approximately 19 Ma, with phocids originating in the North Atlantic or Paratethys region 19–14 Ma. Our understanding of pinniped paleobiology has been enriched by studies that incorporate anatomical and behavioral data into a phylogenetic framework. There is now evidence for sexual dimorphism in the earliest pinnipeds, heralding polygynous breeding systems, followed by increased body sizes, diving capabilities, and diverse feeding strategies in later-diverging phocid and otarioid lineages.

Availability to Steller sea lions (Eumetopias jubatus) of a seasonal prey resource: a prespawning aggregation of eulachon (Thaleichthys pacificus)

2004 ◽  
Vol 61 (8) ◽  
pp. 1475-1484 ◽  
Author(s):  
Michael F Sigler ◽  
Jamie N Womble ◽  
Johanna J Vollenweider
Keyword(s):  
North Pacific Ocean ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Southeast Alaska ◽  
Sea Lions ◽  
The North ◽  
Large Numbers ◽  
Spawning Run ◽  
The North Pacific

The availability of seasonally abundant energy-rich prey can be a significant factor for the survival and reproductive success of predator populations. Large numbers of Steller sea lions (Eumetopias jubatus) were attracted to a prespawning aggregation of eulachon (Thaleichthys pacificus) in Berners Bay in southeast Alaska during April–May in 2002 and 2003. Sea lion abundance increased as eulachon gathered in Berners Bay, peaked as eulachon abundance peaked, and decreased as the eulachon moved up-river. As sea lion abundance increased in Berners Bay, sea lion abundance decreased at Benjamin Island, a sea lion haulout located 22 km away. The eulachon provided an abundant, energy-rich, predictable prey source for the Steller sea lions: (i) eulachon energy density was 9.70 ± 0.24 kJ·g–1, much higher than that of any forage species reported in the North Pacific Ocean except northern lampfish (Stenobrachius leucopsarus); (ii) a large surplus of prey was available per sea lion while the eulachon aggregation was present; and (iii) the spawning run usually begins between late April and early May. The eulachon pulse may be critical to Steller sea lions during a period of high energetic demands.

Geographical restriction as a guide to the causes of extinction: the case of the cold northern oceans during the Neogene

Paleobiology ◽  
1989 ◽  
Vol 15 (4) ◽  
pp. 335-356 ◽  
Author(s):  
Geerat J. Vermeij
Keyword(s):  
Primary Productivity ◽  
North Pacific ◽  
Early Pleistocene ◽  
Northwestern Pacific ◽  
Supporting Evidence ◽  
Geographical Patterns ◽  
The North ◽  
The Pacific ◽  
Late Neogene ◽  
The North Pacific

Geographical restriction to refuges implies the regional extinction of taxa in areas of the previous range falling outside the refuge. A comparison of the circumstances in the refuge with those in areas from which the taxa were eliminated is potentially informative for pinpointing the causes of extinction. A synthesis of data on the geographical and stratigraphical distributions of cool-water molluscs of the North Pacific and North Atlantic Oceans during the late Neogene reveals four patterns of geographical restriction, at least two of which imply that climatic cooling was not the only cause of extinction during the last several million years. These four patterns are (1) the northwestern Pacific restriction, involving 15 taxa whose amphi-Pacific distributions during the late Neogene became subsequently restricted to the Asian side of the Pacific; (2) the northwestern Atlantic restriction, involving six taxa whose early Pleistocene distribution is inferred to have been amphi-Atlantic, but whose present-day and late Pleistocene ranges are confined to the northwestern Atlantic; (3) a vicariant Pacific pattern, in which many ancestral amphi-Pacific taxa gave rise to separate eastern and western descendants; and (4) the circumboreal restriction, involving six taxa whose early Pleistocene distribution, encompassing both the Atlantic and Pacific Oceans, became subsequently limited to the North Pacific. Like the Pliocene extinctions in the Atlantic, previously studied by Stanley and others, the vicariant Pacific pattern is most reasonably interpreted as having resulted from regional extinction of northern populations in response to cooling. The northwestern Pacific and Atlantic restrictions, however, cannot be accounted for in this way. In contrast to the northeastern margins of the Pacific and Atlantic, the northwestern margins are today characterized by wide temperature fluctuations and by extensive development of shore ice in winter. Northeastern, rather than northwestern, restriction would be expected if cooling were the overriding cause of regional extinction. Among the other possible causes of extinction, only a decrease in primary productivity can account for the observed northwestern and circumboreal patterns of restriction. Geographical patterns of body size and the distribution of siliceous deposits provide supporting evidence that primary productivity declined after the Miocene in the northeastern Pacific, but remained high in the northwestern Pacific, and that productivity in the Pacific is generally higher than it is in the Atlantic. The patterns of geographical restriction in the northern oceans thus provide additional support to previous inferences that reductions in primary productivity have played a significant role in marine extinctions.

Sign in / Sign up

Export Citation Format

Share Document