Colonization of the ancient southern oceans by small-sized Phocidae: new evidence from Australia

2020 ◽  
Author(s):  
James P Rule ◽  
Justin W Adams ◽  
Erich M G Fitzgerald
Keyword(s):  
Energy Efficiency ◽  
Southern Ocean ◽  
Late Miocene ◽  
Fossil Record ◽  
Trophic Levels ◽  
Food Chains ◽  
Early Pliocene ◽  
Sea Lions ◽  
Fur Seals ◽  
New Evidence

Abstract Most of the diversity of extant southern true seals (Phocidae: Monachinae) is present in the Southern Ocean, but a poor fossil record means that the origin of this fauna remains unknown. Australia represents a large gap in the record bordering the Southern Ocean that could possibly inform on the origins of the extant Antarctic monachines, with most known fossils remaining undescribed. Here we describe the oldest Australian fossil pinniped assemblage, from the Late Miocene to the Early Pliocene of Beaumaris. Two fossils are referrable to Pinnipedia, five (possibly six) to Phocidae and a humerus is referrable to Monachinae. The humerus is not referrable to any extant tribe, potentially representing an archaic monachine. The description of this assemblage is consistent with the Neogene pinniped fauna of Australia being exclusively monachine before the arrival of otariids (fur seals and sea lions). The Beaumaris humerus, along with other Neogene phocids from the Southern Ocean margins, were smaller than their extant Antarctic relatives, possibly driven by longer food chains with less energy efficiency between trophic levels. This suggests that small archaic phocids potentially used the Southern Ocean as a means of dispersal before the arrival of extant Antarctic monachines.

scholarly journals The oldest known fur seal

2015 ◽  
Vol 11 (2) ◽  
pp. 20140835 ◽  
Author(s):  
Robert W. Boessenecker ◽  
Morgan Churchill
Keyword(s):  
Fossil Record ◽  
Evolutionary History ◽  
Southern California ◽  
Middle Miocene ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal ◽  
Fossil Records ◽  
Phylogenetic Affinities

The poorly known fossil record of fur seals and sea lions (Otariidae) does not reflect their current diversity and widespread abundance. This limited fossil record contrasts with the more complete fossil records of other pinnipeds such as walruses (Odobenidae). The oldest known otariids appear 5–6 Ma after the earliest odobenids, and the remarkably derived craniodental morphology of otariids offers few clues to their early evolutionary history and phylogenetic affinities among pinnipeds. We report a new otariid, Eotaria crypta , from the lower middle Miocene ‘Topanga’ Formation (15–17.1 Ma) of southern California, represented by a partial mandible with well-preserved dentition. Eotaria crypta is geochronologically intermediate between ‘enaliarctine’ stem pinnipedimorphs (16.6–27 Ma) and previously described otariid fossils (7.3–12.5 Ma), as well as morphologically intermediate by retaining an M 2 and a reduced M 1 metaconid cusp and lacking P 2–4 metaconid cusps. Eotaria crypta eliminates the otariid ghost lineage and confirms that otariids evolved from an ‘enaliarctine’-like ancestor.

scholarly journals East Antarctic Ice Sheet and Southern Ocean Response to Orbital Forcing from Late Miocene to Early Pliocene, Wilkes Land, East Antarctica

2021 ◽  
Author(s):  
◽  
Nikita Anne Turton
Keyword(s):  
Southern Ocean ◽  
Late Miocene ◽  
Ice Sheet ◽  
Orbital Forcing ◽  
Sea Ice Extent ◽  
Antarctic Ice Sheet ◽  
Early Pliocene ◽  
Wilkes Land ◽  
Marine Productivity ◽  
East Antarctic Ice Sheet

<p>Geological and ice sheet models indicate that marine-based sectors of the East Antarctic Ice Sheet (EAIS) were unstable during periods of moderate climatic warmth in the past. While geological records from the Middle to Late Pliocene indicate a dynamic ice sheet, records of ice sheet variability from the comparatively warmer Late Miocene to Early Pliocene are sparse, and there are few direct records of Antarctic ice sheet variability during this time period. Sediment recovered in Integrated Ocean Drilling Program U1361 drill core from the Wilkes Land margin provides a distal but continuous glacially-influenced record of the behaviour of Antarctic Ice Sheets.  This thesis presents marine sedimentological and x-ray fluorescence geochemical datasets in order to assess changes in the dynamic response of the EAIS and Southern Ocean productivity in the Wilkes Land sector during Late Miocene and Early Pliocene to climatic warming and orbital forcing between 6.2 and 4.4 Ma. Two primary lithofacies are identified which can be directly related to glacial–interglacial cycles; enhanced sedimentation during glacials is represented by low-density turbidity flows that occurred in unison with low marine productivity and reduced iceberg rafted debris. Interglacial sediments contain diatomaceous muds with short-lived, large fluxes of iceberg rafted debris preceding a more prolonged phase of enhanced marine productivity. Interglacial sediments coincide with a more mafic source of terrigenous sediment, interfered to be associated with an inland retreat of the ice margin resulting in erosion of lithologies that are currently located beneath the grounded EAIS. Poleward invigoration of the Antarctic Circumpolar Current during glacial–interglacial transitions is proposed to have intensified upwelling, enhancing nutrient availability for marine productivity, and increasing oceanic heat flux at the ice margin acting to erode marine ice sheet grounding lines and triggering retreat.  Spectral analysis of the datasets indicated orbital frequencies are present in the iceberg rafted debris mass accumulation rates at all three Milankovitch frequencies, with a dominant 100 kyr eccentricity driven ice discharge. Prolonged intervals of marine productivity correlate to 100 kyr cyclicity occurring at peaks in obliquity. The response of both ice sheet and biological systems to 100 kyr cyclicity may indicate eccentricity-modulated sea ice extent controls the influx of warm water onto the continental shelf.</p>

scholarly journals East Antarctic Ice Sheet and Southern Ocean Response to Orbital Forcing from Late Miocene to Early Pliocene, Wilkes Land, East Antarctica

2021 ◽  
Author(s):  
◽  
Nikita Anne Turton
Keyword(s):  
Southern Ocean ◽  
Late Miocene ◽  
Ice Sheet ◽  
Orbital Forcing ◽  
Sea Ice Extent ◽  
Antarctic Ice Sheet ◽  
Early Pliocene ◽  
Wilkes Land ◽  
Marine Productivity ◽  
East Antarctic Ice Sheet

<p>Geological and ice sheet models indicate that marine-based sectors of the East Antarctic Ice Sheet (EAIS) were unstable during periods of moderate climatic warmth in the past. While geological records from the Middle to Late Pliocene indicate a dynamic ice sheet, records of ice sheet variability from the comparatively warmer Late Miocene to Early Pliocene are sparse, and there are few direct records of Antarctic ice sheet variability during this time period. Sediment recovered in Integrated Ocean Drilling Program U1361 drill core from the Wilkes Land margin provides a distal but continuous glacially-influenced record of the behaviour of Antarctic Ice Sheets.  This thesis presents marine sedimentological and x-ray fluorescence geochemical datasets in order to assess changes in the dynamic response of the EAIS and Southern Ocean productivity in the Wilkes Land sector during Late Miocene and Early Pliocene to climatic warming and orbital forcing between 6.2 and 4.4 Ma. Two primary lithofacies are identified which can be directly related to glacial–interglacial cycles; enhanced sedimentation during glacials is represented by low-density turbidity flows that occurred in unison with low marine productivity and reduced iceberg rafted debris. Interglacial sediments contain diatomaceous muds with short-lived, large fluxes of iceberg rafted debris preceding a more prolonged phase of enhanced marine productivity. Interglacial sediments coincide with a more mafic source of terrigenous sediment, interfered to be associated with an inland retreat of the ice margin resulting in erosion of lithologies that are currently located beneath the grounded EAIS. Poleward invigoration of the Antarctic Circumpolar Current during glacial–interglacial transitions is proposed to have intensified upwelling, enhancing nutrient availability for marine productivity, and increasing oceanic heat flux at the ice margin acting to erode marine ice sheet grounding lines and triggering retreat.  Spectral analysis of the datasets indicated orbital frequencies are present in the iceberg rafted debris mass accumulation rates at all three Milankovitch frequencies, with a dominant 100 kyr eccentricity driven ice discharge. Prolonged intervals of marine productivity correlate to 100 kyr cyclicity occurring at peaks in obliquity. The response of both ice sheet and biological systems to 100 kyr cyclicity may indicate eccentricity-modulated sea ice extent controls the influx of warm water onto the continental shelf.</p>

Micromys caesaris, a new murid (Rodentia, Mammalia) from the Late Pliocene of the Guadix Basin, southeastern Spain

2008 ◽  
Vol 82 (2) ◽  
pp. 436-441 ◽  
Author(s):  
Raef Minwer-Barakat ◽  
Antonio García-Alix ◽  
Elvira Martín-Suárez ◽  
Matthijs Freudenthal
Keyword(s):  
Late Miocene ◽  
Fossil Record ◽  
Fossil Species ◽  
Late Pliocene ◽  
Early Pliocene ◽  
Southeastern Spain ◽  
Extant Species ◽  
North Asia ◽  
Micromys Minutus

The Genus Micromys includes a single extant species, Micromys minutus (Pallas, 1771), which lives in Europe and North Asia. This genus is known in the fossil record since the late Miocene; eight fossil species have been described in Europe and Asia, most of them of late Miocene and early Pliocene age. The evolution of this genus during the late Pliocene is barely known. Although it is present in numerous localities of this age, remains of Micromys are usually scarce and generally assigned to the species M. minutus or M. praeminutus Kretzoi, 1959.

scholarly journals The oldest known fur seal

2017 ◽  
Author(s):  
Robert Boessenecker ◽  
Morgan Churchill
Keyword(s):  
Fossil Record ◽  
Evolutionary History ◽  
Southern California ◽  
Middle Miocene ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal ◽  
Fossil Records ◽  
Phylogenetic Affinities

The poorly known fossil record of fur seals and sea lions (Otariidae) does not reflect their current diversity and widespread abundance. This limited fossil record contrasts with the more complete fossil records of other pinnipeds such as walruses (Odobenidae). The oldest known otariids appear 5-6 Ma after the earliest odobenids, and the remarkably derived craniodental morphology of otariids offers few clues to their early evolutionary history and phylogenetic affinities among pinnipeds. We report a new otariid, Eotaria crypta, from the early middle Miocene “Topanga” Formation (15-17.5 Ma) of southern California, represented by a partial mandible with well-preserved dentition. Eotaria crypta is geochronologically intermediate between “enaliarctine” stem pinnipedimorphs (16.6-27 Ma) and previously described otariid fossils (7.3-12.5 Ma), as well as morphologically intermediate by retaining an M2 and a reduced M1 metaconid cusp and lacking P2-4 metaconid cusps. Eotaria crypta eliminates the otariid ghost lineage and confirms that otariids evolved from an “enaliarctine”-like ancestor.

Diversification and extinction patterns among Neogene perimediterranean mammals

1989 ◽  
Vol 325 (1228) ◽  
pp. 401-420 ◽  
Keyword(s):  
Late Miocene ◽  
Fossil Record ◽  
Driving Forces ◽  
High Rate ◽  
Eastern Africa ◽  
European Continent ◽  
Southern France ◽  
Early Pliocene ◽  
Faunal Turnover ◽  
Extinction Event

The best mammalian fossil record during the Neogene of Western Europe is that of the rodents, the most successful and diversified mammal order. The study of origination and extinction during the Neogene (24-3 Ma BP) in one of the best documented areas, Spain and southern France, gives an insight into the dynamics of these communities and indicates the possible nature of the driving forces. Three main periods of time show a high rate of origination: the late Burdigalian (17.5 Ma BP), the early Vallesian (11.5-11 Ma BP) and the early Pliocene (4.2- 3.8 Ma BP). Two of these high origination-rate periods are immediately followed by important extinction events during which all cohorts are deeply affected (11.5-11 Ma BP and 4.2- 3.8 Ma BP). The most important extinction event seems to occur during the early Vallesian (11.5-11 Ma BP), which probably includes the middle/late Miocene boundary. At the Miocene/Pliocene boundary, and during the early Pliocene, the faunal turnover seems to become faster, inducing a strong decrease of the mean species duration. Whereas the main immigration event, which occurs at 17.5 Ma BP, can be related to other faunal migrations in terms of the closure of the Tethys, as it occurs also in eastern Africa and in southwest Asia, the middle/late Miocene boundary event may have been related to a period of ice growth in the Southern Hemisphere. The extinction event that affects the planktonic foraminifera at 12 Ma BP cannot be chronologically correlated to this southwestern European land-mammal extinction event, because the calibration of the marine fossil record during that time-span has to be precise. Some limited terrestrial faunal exchanges that occur during the Messinian between southwestern Europe and northwestern Africa do not deeply affect the general faunal dynamics. Both allochthonous cohorts of immigrants become rapidly extinct. Several endemic rodent faunas, indicating insular conditions, have been reported from the southern edge of the western European continent from the middle Miocene up to the Pliocene. All show low taxonomic diversity, strong endemism and short survival. Some of them, like those of the Gargano Islands during the late Miocene, underwent peculiar morphological changes and also speciation. The large number of rodent genera coevolving in the Gargano Islands is indicative of the large surface areas of these islands. The general geographic pattern of southwestern Europe during the Neogene may therefore correspond to a large continental province including Spain and southern France with some kind of fast-modifying archipelago on its southern rim.

Evidence for iceberg armadas from East Antarctica in the Southern Ocean during the late Miocene and early Pliocene

2010 ◽  
Vol 290 (3-4) ◽  
pp. 351-361 ◽  
Author(s):  
Trevor Williams ◽  
Tina van de Flierdt ◽  
Sidney R. Hemming ◽  
Elena Chung ◽  
Martin Roy ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Late Miocene ◽  
East Antarctica ◽  
Early Pliocene
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