scholarly journals Eocene neoselachians from the La Meseta formation, Seymour Island, Antarctic Peninsula

1980 ◽  
Vol 329 ◽  
pp. 1-10
Author(s):  
Bruce J Welton ◽  
William J. Zinsmeister
Keyword(s):  
Antarctic Peninsula ◽  
La Meseta Formation ◽  
Seymour Island

The youngest record of fossil land mammals from Antarctica; its significance on the evolution of the terrestrial environment of the Antarctic Peninsula during the late Eocene

1997 ◽  
Vol 71 (2) ◽  
pp. 348-350 ◽  
Author(s):  
S. F. Vizcaino ◽  
M. Bond ◽  
M. A. Reguero ◽  
R. Pascual
Keyword(s):  
Antarctic Peninsula ◽  
Present Note ◽  
Late Eocene ◽  
South American ◽  
Terrestrial Environment ◽  
Shallow Marine ◽  
Early Oligocene ◽  
La Meseta Formation ◽  
The Antarctic ◽  
Seymour Island

The record of fossil land mammals from Antarctica has been restricted previously to the middle levels of the Eocene-?early Oligocene La Meseta Formation in Seymour Island, Antarctic Peninsula. This mostly shallow-marine sequence was divided informally into seven subunits (Tertiary Eocene La Meseta or TELM 1 to 7) by Sadler (1988). Land mammals, representing South American lineages of marsupials, edentates, and ungulates were recovered from TELM 3, 4, and 5 (Marenssi et al., 1994; Vizcaíno et al., 1994). The purpose of the present note is to report the discovery of a well-preserved ungulate tooth from the uppermost level of the La Meseta Formation (TELM 7) and to discuss its paleoenvironmental implications.

Eocene crinoids from Seymour Island, Antarctic Peninsula: paleobiogeographic and paleoecologic implications

1993 ◽  
Vol 67 (2) ◽  
pp. 250-257 ◽  
Author(s):  
David L. Meyer ◽  
Tatsuo Oji
Keyword(s):  
Antarctic Peninsula ◽  
Surface Waters ◽  
Systematic Position ◽  
La Meseta Formation ◽  
Mode Of Life ◽  
The Antarctic ◽  
Favorable Temperature ◽  
A New Species ◽  
Seymour Island ◽  
Water Facies

On the basis of recent collections from the Upper Eocene La Meseta Formation of Seymour Island, Antarctic Peninsula, the morphology, systematic position, taphonomy, and paleoecology of the isocrinid Metacrinus fossilis are investigated. A new species, Notocrinus rasmusseni, is described as the first comatulid crinoid known from the Antarctic fossil record. The systematic assignment of M. fossilis is maintained. Basal abrasion of calyxes and absence of long attached columns suggest that M. fossilis might have lost most of the column in adult stages and lived directly on the substratum, supported by some arms and a few cirri, similar to comatulids. About 10 percent of M. fossilis individuals show brachial regeneration, in contrast to regeneration frequencies of 70–90 percent among modern Japanese isocrinids. The anomalous occurrence of isocrinids in shallow-water facies of the La Meseta is attributed to a combination of reduced predation pressure, the presumed stalkless mode of life, and a favorable temperature regime in Antarctic surface waters prior to the onset of cooling at the close of the Eocene.

scholarly journals The earliest fossil record of a medium-sized penguin

2011 ◽  
Vol 32 (3) ◽  
pp. 269-277 ◽  
Author(s):  
Piotr Jadwiszczak ◽  
Sandra Chapman
Keyword(s):  
Antarctic Peninsula ◽  
Early Phase ◽  
Fossil Record ◽  
Taxonomic Diversity ◽  
Distal Humerus ◽  
Early Eocene ◽  
British Antarctic Survey ◽  
Early Eocene Climatic Optimum ◽  
La Meseta Formation ◽  
Seymour Island

The earliest fossil record of a medium-sized penguinThe fossil record of Antarctic Sphenisciformes dates as early as the late Palaeocene Cross Valley Formation, Seymour Island, Antarctic Peninsula. However, the best known Antarctic locality for early penguin remains (mainly isolated bones) is the Eocene La Meseta Formation that outcrops in the northeast of Seymour Island. The analysis of an unstudied set of specimens collected there by members of the British Antarctic Survey in 1989 has resulted in identification of a distal humerus from the unit Telm3 (early Eocene) of the formation that is the oldest known bone attributable to a medium-sized (in the context of the entire Cainozoic era) penguin. This find suggests that the origin of these birds, in conjunction with an increase in taxonomic diversity of the Eocene Sphenisciformes, was related to the Early Eocene Climatic Optimum (EECO) or, more probably, the early phase of subsequent cooling.

Record of Late Miocene glacial deposits on Isla Marambio (Seymour Island), Antarctic Peninsula

2009 ◽  
Vol 22 (2) ◽  
pp. 193-198 ◽  
Author(s):  
Sergio A. Marenssi ◽  
Silvio Casadío ◽  
Sergio N. Santillana
Keyword(s):  
Antarctic Peninsula ◽  
Late Miocene ◽  
Late Eocene ◽  
Weddell Sea ◽  
Volcanic Group ◽  
Lower Oligocene ◽  
La Meseta Formation ◽  
James Ross Island ◽  
Stratigraphic Sequences ◽  
Seymour Island

AbstractWe report and describe two new small diamictite outcrops on Isla Marambio (Seymour Island), Antarctic Peninsula. These rocks rest on an erosional unconformity on top of the Eocene La Meseta Formation and are unconformably covered by glaciomarine rocks of the ?Pliocene–Pleistocene Weddell Sea Formation. The lithology, fossil content and isotopic ages obtained strongly suggest that the rocks belong to the Hobbs Glacier Formation and support a Late Miocene age for this unit. Additionally, the dated basalt clast provides the oldest age (12.4 Ma) for the James Ross Island Volcanic Group recorded up to now. The here described diamictite cannot be confidently correlated with a glaciomarine unit previously assigned to the Late Eocene–Lower Oligocene taken as proof that initial expansion of ice on Antarctica encompassed the entire continent synchronously in the earliest Oligocene. However, it is now evident that there are likely to be more, short but important, stratigraphic sequences of key regional and Antarctic wide interest preserved on the plateau of Isla Marambio.

Definitive specimens of Merlucciidae (Gadiformes) from the Eocene James Ross Basin of Isla Marambio (Seymour Island), Antarctic Peninsula

2012 ◽  
Vol 24 (5) ◽  
pp. 467-472 ◽  
Author(s):  
Kerin M. Claeson ◽  
Joseph T. Eastman ◽  
Ross D. E. Macphee
Keyword(s):  
Antarctic Peninsula ◽  
Deep Sea ◽  
Fossil Record ◽  
Middle Eocene ◽  
Mental Foramen ◽  
The Arctic ◽  
Lateral Aspect ◽  
La Meseta Formation ◽  
Freshwater Environments ◽  
Seymour Island

AbstractAn isolated partial right dentary (BAS D.515.2) collected by the British Antarctic Survey prompted a re-evaluation of gadiform remains from the La Meseta Formation (conventionally middle Eocene) of Isla Marambio (Seymour Island), Antarctic Peninsula. Modern gadiforms (hakes and cods) range from the Arctic to Antarctic, inhabiting deep sea benthic, shore, estuarine, and freshwater environments. Based on a fossil record primarily composed of otoliths, they are known to extend back to the Eocene and Oligocene. The new specimen was recovered from the fossil penguin locality D.515. It is characterized by a single row of sharp, ankylosed teeth set upon robust bony pedestals. The surface anterior to the mental foramen exhibits ascending and descending ridges with slightly rugose texture. The ascending ridge is fractured, but partially covers the lateral aspect of the tooth row. BAS D.515.2 is unlike the dentary of macrourid gadiforms, also recovered from the Eocene of Antarctica. BAS D.515.2 preserves several features similar to previously published accounts of the gadiform “†Mesetaichthys” from Isla Marambio. These specimens are probably the same taxon and their combined character suite indicates it is a member of Merluccidae. Thus, these are the only non-otolithic skeletal specimens of an Eocene hake known outside of the London Clay's †Rhinocephalus.

Penguin cranial remains from the Eocene La Meseta Formation, Isla Marambio (Seymour Island), Antarctic Peninsula

2011 ◽  
Vol 23 (4) ◽  
pp. 369-378 ◽  
Author(s):  
Carolina Acosta Hospitaleche ◽  
Nadia Haidr
Keyword(s):  
Antarctic Peninsula ◽  
Niche Partitioning ◽  
Trophic Preferences ◽  
La Meseta Formation ◽  
High Diversity ◽  
Seymour Island ◽  
Partitioning Strategy

AbstractWidely accepted ideas about trophic preferences of early penguins suggest that all Eocene sphenisciforms were piscivorous. However, recent findings from the La Meseta Formation (Eocene) of Antarctica, support the presence of at least two different morphotypes that may have evolved as a niche partitioning strategy, which is consistent with the high diversity recorded. The first of them corresponds to a medium–large sized penguin, resembling the Neogene species in configuration. Another morphotype is represented by extremely large penguins with very long and slender bills, clearly linked to fish catching habits.

Late Eocene gadiform (Teleostei) skull from Seymour Island, Antarctic Peninsula

1991 ◽  
Vol 3 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Joseph T. Eastman ◽  
Lance Grande
Keyword(s):  
Antarctic Peninsula ◽  
Late Eocene ◽  
Climatic Conditions ◽  
Convincing Evidence ◽  
Posterior Half ◽  
Antarctic Region ◽  
La Meseta Formation ◽  
The Antarctic ◽  
First Time ◽  
Seymour Island

On the basis of a skull from the late Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, a gadiform fish is reported from the Antarctic region for the first time. This specimen, the most completely preserved fossil teleost cranium yet described from Antarctica, provides convincing evidence for the presence of Gadiformes in a far southerly location under temperate climatic conditions 40 m.y. ago. The exoccipital condyles, supraoccipital and lambdoidal crests, and post-temporal and supratemporal fossae are well preserved, as are the roofing bones on the posterior half of the skull. Comparative osteological study indicates that these features are very similar in appearance to those of merlucciids (hakes) and gadids (cods).

An Eocene tardigrade (Mammalia, Xenarthra) from Seymour Island, West Antarctica

1995 ◽  
Vol 7 (4) ◽  
pp. 407-408 ◽  
Author(s):  
Sergio F. Vizcaíano ◽  
Gustavo J. Scillato-Yané
Keyword(s):  
Antarctic Peninsula ◽  
West Antarctica ◽  
Shallow Marine ◽  
Lower Miocene ◽  
La Meseta Formation ◽  
Seymour Island

Carlini et al. (1990) reported the presence of Xenarthra (Mammalia) from the Eocene deposits of Seymour Island, Antarctic Peninsula, based on an ungual phalanx from locality RV 8200. The locality, referred to informally as “mammal site” by Woodburne & Zinsmeister (1984), is located at 64°14′21″S, 56°39′44″W at an elevation of 45 m in the middle levels of the shallow marine La Meseta Formation (TELM 5 of Saddler 1988). Carlini et al. (1990) initially identified the phalanx as a megatherioid sloth (Order Tardigrada). Marenssi et al. (1994) revised its identification to ?Tardigrada or ?Vermilingua, by comparison with a primitive myrmecophagid (Order Vermilingua) from the Lower Miocene of Patagonia, whose ungual phalanges are indistinguishable from those of primitive sloths (Carlini et al. 1992). We report a fragmentary tooth of a member of the Tardigrada (Family incertue sedis) confirming the presence of this group in the Eocene of Antarctica.

Antarctomithrax thomsoni,a new genus and species of crab (Brachyura; Majidae) from the La Meseta Formation (Eocene) of Seymour Island, Antarctica

1994 ◽  
Vol 68 (1) ◽  
pp. 174-176 ◽  
Author(s):  
Rodney M. Feldmann
Keyword(s):  
Antarctic Peninsula ◽  
Late Cretaceous ◽  
New Genus ◽  
High Energy ◽  
Lower Latitude ◽  
Decapod Crustaceans ◽  
New Genus And Species ◽  
La Meseta Formation ◽  
The Antarctic ◽  
Seymour Island

The james ross basin, situated on the eastern margin of the Antarctic Peninsula, has yielded an extensive fauna of decapod crustaceans spanning Late Cretaceous through Eocene time. To date, 28 species in 22 genera and 18 families have been described (Feldmann, 1992; Feldmann, Tshudy, and Thomson, 1993), making this the most diverse fossil decapod fauna in the Southern Hemisphere. Within the basin, Seymour Island alone contains rocks of the Eocene age La Meseta Formation from which seven species of crabs, one galatheid, and one species of callianassid ghost shrimp have been described (Feldmann and Zinsmeister, 1984; Feldmann and Wilson, 1988; Feldmann, 1992). The fauna of the La Meseta is remarkable also because, although the organisms are preserved in rocks deposited in moderate- to high-energy, shallow-water habitats (Elliot and Trautman, 1982), many of the species represent early occurrences of taxa with living descendants that are characteristic of deeper water, lower latitude habitats (Zinsmeister and Feldmann, 1984).

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