scholarly journals Peer Review #2 of "The oldest record of the Steller sea lion Eumetopias jubatus (Schreber, 1776) from the early Pleistocene of the North Pacific (v0.1)"

2020 ◽  
Author(s):  
J Velez-Juarbe
Keyword(s):  
Peer Review ◽  
North Pacific ◽  
Early Pleistocene ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
The North ◽  
The North Pacific

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.

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.

Revision of the genus Anophryocephalus Baylis, 1922 from pinnipeds in the Holarctic, with descriptions of Anophryocephalus nunivakensis sp.nov. and A. eumetopii sp.nov. (Tetrabothriidae) and evaluation of records from the Phocidae

1991 ◽  
Vol 69 (6) ◽  
pp. 1653-1668 ◽  
Author(s):  
Eric P. Hoberg ◽  
Ann M. Adams ◽  
Robert L. Rausch
Keyword(s):  
Bering Sea ◽  
North Pacific ◽  
Pacific Basin ◽  
Genital Papilla ◽  
High Latitudes ◽  
Eumetopias Jubatus ◽  
The North ◽  
Phoca Largha ◽  
The North Pacific ◽  
North Pacific Basin

Anophryocephalus Baylis, 1922 is emended to include tetrabothriid cestodes with intricate scolices (paired auricular appendages and bothridial operculae), complex genital atria (muscular chamber ventral to the vagina; muscular pad adjacent to the aperture of the male canal), and atrophy of the dorsal osmoregulatory system. Anophryocephalus anophrys (type), A. skrjabini, and A. ochotensis are redescribed. Anophryocephalus nunivakensis sp.nov., from Phoca largha, has bothridial operculae with broad anterior apertures, an ovoid cirrus sac (57–95 μm in diameter), a ventrolaterally directed male canal (26–44 μm long in mature segments), and 26–56 testes. Anophryocephalus eumetopii sp.nov., from Eumetopias jubatus, has bothridial operculae with narrow, slitlike, diagonally directed apertures, a spheroidal cirrus sac (51–72 μm in diameter), a prominent genital papilla and ventrolaterally directed male canal (36–51 μm long in mature segments), and 32–66 testes. Postlarval ontogeny of the scolex among some species of Anophryocephalus appears similar to that known for Tetrabothrius spp., suggesting uniformity in morphogenesis of the holdfast among the Tetrabothriidae. Anophryocephalus spp. are typical parasites of pinnipeds in the Holarctic, and contrary to previous reports, A. skrjabini and A. ochotensis are exclusively parasites of Phoca spp. and Eumetopias jubatus, respectively, at high latitudes in the North Pacific basin and Bering Sea.

Northeastern Pacific Pleistocene Sea Otters

1966 ◽  
Vol 23 (12) ◽  
pp. 1897-1911 ◽  
Author(s):  
Edward Mitchell
Keyword(s):  
North Pacific ◽  
Early Pleistocene ◽  
Sea Otter ◽  
Sea Otters ◽  
The North ◽  
San Pedro ◽  
Northeastern Pacific ◽  
Living Species ◽  
Santa Rosa Island ◽  
The North Pacific

Previously known by only one fossil bone from Oregon, the record of the sea otter is supplemented by description of 11 bones newly found in Late Pleistocene deposits at San Pedro and on Santa Rosa Island and one tooth from an Early Pleistocene deposit at San Pedro, southern California, all considered representative of the living species Enhydra lutris. Faunal associations suggest that the animals lived with cool-water faunas in areas of shallow to moderate depth near islands. The long-accepted hypothesis that E. lutris evolved from "Lutra reevei" during the Pliocene in the North Atlantic and migrated to the North Pacific is rejected on chronologic and zoogeographic grounds. The sea otter may be a North Pacific endemic autochthon.

scholarly journals Pliocene to Pleistocene climate and environmental history of Lake El'gygytgyn, Far East Russian Arctic, based on high-resolution inorganic geochemistry data

2014 ◽  
Vol 10 (4) ◽  
pp. 1381-1399 ◽  
Author(s):  
V. Wennrich ◽  
P. S. Minyuk ◽  
V. Borkhodoev ◽  
A. Francke ◽  
B. Ritter ◽  
...  
Keyword(s):  
North Pacific ◽  
Far East ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Gradual Transition ◽  
Russian Arctic ◽  
Lake Productivity ◽  
The North ◽  
Lake El’Gygytgyn ◽  
The North Pacific

Abstract. The 3.6 Ma sediment record of Lake El'gygytgyn/NE Russia, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition as determined by X-ray fluorescence scanning exhibits significant changes since the mid-Pliocene caused by climate-driven variations in primary production, postdepositional diagenetic processes, and lake circulation as well as weathering processes in its catchment. During the mid- to late Pliocene, warmer and wetter climatic conditions are reflected by elevated Si / Ti ratios, indicating enhanced diatom production in the lake. Prior to 3.3 Ma, this signal is overprinted by intensified detrital input from the catchment, visible in maxima of clastic-related proxies, such as K. In addition, calcite formation in the early lake history points to enhanced Ca flux into the lake caused by intensified weathering in the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the development of permafrost in the region triggered by cooling in the mid-Pliocene. After ca. 3.0 Ma the elemental data suggest a gradual transition to Pleistocene-style glacial–interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 kyr obliquity band but experienced a change to a 100 kyr eccentricity dominance during the middle Pleistocene transition (MPT) at ca. 1.2–0.6 Ma. This clearly demonstrates the sensitivity of the Lake El'gygytgyn record to orbital forcing. A successive decrease of the baseline levels of the redox-sensitive Mn / Fe ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall change in the bottom-water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Pleistocene. The coincidence with major changes in the North Pacific and Bering Sea paleoceanography at ca. 1.8 Ma implies that the change in lake hydrology was caused by a regional cooling in the North Pacific and the western Beringian landmass and/or changes in the continentality. Further increases in total organic carbon and total nitrogen content after ca. 1.6 Ma are attributed to reduced organic matter decay in the sediment during prolonged anoxic periods. This points to more extensive periods of perennial ice coverage, and thus, to a progressive shifts towards more intense peak glacial periods. In the course of the Pleistocene glacial–interglacial sequence eight so-called "super-interglacials" occur. Their exceptionally warm conditions are reflected by extreme Si / Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating extraordinary high lake productivity.

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.

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