An eocene leatherback turtle (Cryptodira : Dermochelyidae) from Seymour Island, Antartica (original) (raw)
Related papers
Argentine—Polish geological investigations on Seymour (Marambio) Island, Antarctic Peninsula, 1992
This report describes aims and preliminary results of geological fieldwork carried out by a joint Argentine-Polish party on Seymour (Marambio) and Cockburn islands. Antarctic Peninsula, during austral summer of 1987 88. Seymour Island exposes chiefly shallow-marine, fossiliferous siliciclastic sediments that form an upper, 2000 m thick part in the Mesozoic-Tertiary backarc basin-infill of the Antarctic Peninsula. The fieldwork centered on paleontology and sedimentology of the La Meseta Formation (upper Eocene-?lower Oligocene), although some observations of older deposits were carried out also. Clupeoid fishes were discovered in the La Meseta Formation. This is the first record of such fish fossils on the Antarctic continent.
Argentine-Polish geological investigations on Seymour (Marambio) Island, Antarctica, 1988
Polish Polar Research
Argentine-Polish geological investigations on Seymour (Marambio) Island, Antarctica, 1988 ABSTRACT: This report describes aims and preliminary results of geological fieldwork carried out by a joint Argentine-Polish party on Seymour (Marambio) and Cockburn islands. Antarctic Peninsula, during austral summer of 1987 88. Seymour Island exposes chiefly shallow-marine, fossiliferous siliciclastic sediments that form an upper, 2000 m thick part in the Mesozoic-Tertiary backarc basin-infill of the Antarctic Peninsula. The fieldwork centered on paleontology and sedimentology of the La Meseta Formation (upper Eocene-?lower Oligocene), although some observations of older deposits were carried out also. Clupeoid fishes were discovered in the La Meseta Formation. This is the first record of such fish fossils on the Antarctic continent.
Advances in Polar Science, 2019
Antarctica has significant environmental, scientific, historic, and intrinsic values, all of which are worth protecting into the future. This continent has a discrete number of places of scientific interest that exhibit great potential as natural heritage sites; its geodiversity is of fundamental importance to scientific values of the continent, and the pursuit of geological and paleontological knowledge has had a strong influence on its historical values. Seymour Island was once called the 'Rosetta Stone' of Southern Hemisphere paleobiology, because this small island provides the most complete and richly fossiliferous Late Cretaceous-Paleogene sequence in Antarctica. In particular, fossil vertebrates form part of the evidence used in reconstructing the history of life on Antarctica. Paleontological heritage is considered a subset of geo-heritage that embodies both natural and historical components which has received only indirect recognition. Seymour Island is an outstanding paleontological area with high heritage value of its Late Cretaceous/Paleogene vertebrates and should be considered for geo-conservation and protection. This paper reviews vertebrate fossil occurrences and outcrops on Seymour Island and discusses some threats to these fossil sites.
The oldest mammals from Antarctica, early Eocene of the La Meseta Formation, Seymour Island
Palaeontology, 2014
New fossil mammals found at the base of Acantilados II Allomember of the La Meseta Formation, from the early Eocene (Ypresian) of Seymour Island, represent the oldest evidence of this group in Antarctica. Two specimens are here described; the first belongs to a talonid portion of a lower right molar assigned to the sparnotheriodontid litoptern Notiolofos sp. cf. N. arquinotiensis. Sparnotheriodontid were medium-to large-sized ungulates, with a wide distribution in the Eocene of South America and Antarctica. The second specimen is an intermediate phalanx referred to an indeterminate Eutheria, probably a South American native ungulate. These Antarctic findings in sediments of 55.3 Ma query the minimum age needed for terrestrial mammals to spread from South America to Antarctica, which should have occurred before the final break-up of Gondwana. This event involves the disappearance of the land bridge formed by the Weddellian Isthmus, which connected West Antarctica and southern South America from the Late Cretaceous until sometime in the earliest Palaeogene.
Journal of South American Earth Sciences, 1991
Approximately 150 meters of fine-grained Campanian sediments and over 100 meters of fine-to medium-grained Eocene sands underlie Pliocene basalts and conglomerates on Cockburn Island, northeastern Antarctic Peninsula. The Campanian beds are part of the "Unnamed strata" of the Marambio Group and contain invertebrate and palynomorph fossils that predate the adjacent Seymour Island L6pez de Bertodano succession. Rich palynomorph floras suggest a middle Campanian age. Deposition was in low energy, shallow shelf environments. Invertebrate and palynomorph fossils, and lithology, all indicate correlation of the Eocene beds with the basal La Meseta Formation, members Telm I and lower Telm 2 of Seymour Island. The age of these beds is probably late early Eocene. The basal La Meseta sands are marginal marine to shallow shelf sediments that fill a broad valley probably incised during latest Paleocene-earliest Eocene as a result of toctonism and sea-level lowstands.
Journal of South American Earth Sciences, 1994
Abztraet-A thick, largely shallow marine succession of Cretaceous and Lower Tertiary strata, deposited in the James Ross Basin, is well exposed on an archipelago of islands at the northern end oftbe Antarctic Peninsula. This succession was thought to be relatively continuous, partieuharly on Seymour Island where a thick Upper Cretaceous succession passes up into Paleocene and Eocene strata. Several onconformities present in the succession were thought to be relatively minor and have been ascribed to sea level changes. Equivalent sedimentary deposits of the L6pez de Bertodano and La Meseta formations, Campanian/Maastrichtian and Lower Eocene respectively, are exposed on Coekburn Island, less than 10 km from Seymour Island. The contact between the two units is an unconformity with an angular discordance varying from 20* to 55". Rotation of the L6pez de Bertodano Formation corresponds with syn-sedimentary disruption elsewhere in the basin throughout the Late Cretaceous and points to persistent iostability. The ages of the strata on either side of the onconformity have been dated on the palynologieal content of five samples and correlation with the Seymour Island succession suggests that at least 900 m of Cretaceous (650 m) and Lower Tertiary (250 m) strata are missing from, or were not deposited at, Cockbum Island. Reworked Maastrichtian palynomorphs in a breccia bed within the La Mnseta Formation confirm that Upper Cretaceous strata were eroded although there is no evidence for reworking of Paleocene sediments. We conclude that Cockburn Island includes a continuation of the Eocene unconformity of Seymour Island, extending the trend for the base of the La Meseta Formation to onlap onto progressively older strata. This unconformity may mark a major phase of basin inversion, with tilting and uplift possibly affecting much of the James Ross Basin at this time. Reaumen-La grnesa sucesi6n C.retlcico y Tereiario inferior, dominantemente marino poco profundo de la cuenea de James Ross eata bien expneata on un archipielago de ishas en el extremo norte de la peninzula Antartiea, particularmente en la isla Seymour donde la gruesa sucesidn de el CretAcico superior pasa a los ostratos de el Paleoceno y Eoceno. Las varias ineonformidades presentes en la sucesi6n son concideradas menores y atribuidas a camhius de el nivel del mar. Los dep6sitos equivalentes de las Formaciones L61~z de Bertadano y La Meseta, Campaniano/Maaatrichtiano y Eocene inferior respeetivamente estan expuestas en la isla Coekburn a menos de 10 km de de la isla Seymour. El eontacto entre las dos unidades es una ineonformidad angular entre 20 °-55 °. Per rotagi6n de la Formagi6n L6pez de Bertodano corresponde con una discontinuidad sin-sedimentaria de finales de el Cret~ico a trav6s de la cnenea. Dataeiones palinol6gicas de los estratos de cada hado de la inconformidad y correlaei6n con ha sucesidu de la ~ Seymour sugiere qne al menns 900 m, 650m de Cretheico y 250 m de Terciario estan desaparecidos o fuer6n no depositaries eta la isla Cockburn. Aunqne no hay evideneia de retrabajamiento de sedimentos Paleocenos, la presencia de palinomorfos de edad maaatrichtiana retrabajados en una breeha dentro de la Formaci6n La Meseta confirma que estratos de el Cret(wico superior fner6n erodadns. Coneluimns queen la iala Conekburn hay una cot3tinuidad de la inconformidad Eocena de la isla Seymour, extondiendo el tren a la base de ha Formaci6n La Meseta transgrediendo estratos progresivamente m~ antfguos. Eata inconfonnided puede marear ona fase mayor de inversi6n, con inclinaei6n y levantamiento afectando pnsiblemente la mayor parle de ha euenca de James Ross durante este tiempo.
Ameghiniana, 2016
Notiolofos arquinotiensis is the most abundant terrestrial placental mammal in the Paleogene of the Antarctic continent. Evidence suggests a South American origin of Sparnotheriodontidae, and an allopatric speciation event for the appearance of N. arquinotiensis. It was recorded exclusively on Seymour Island, through most of the La Meseta and Submeseta formations. Isotopic and paleomagnetic calibration of the units indicate a relatively continuous fossil record of at least 17.5 Ma. The stasis hypothesis is tested here as opposite to the possibility of a wider and previously non-identified specific diversity of Antarctic sparnotheriodontids. The material of N. arquinotensis available was compared in preservation, characters and dental occlusal areas to the more complete phylogenetic relative Sparnotheriodon epsilonoides and the North American Meniscotherium chamense. Despite there being no close phylogenetic relationship between Notiolofos and Meniscotherium, the morphological dental similarity between them suggests they could be interpreted as ecologically equivalent taxa. The analysis allows the reassignment of some N. arquinotensis teeth to other dental loci. The results indicate that there are no reasons to justify the presence of different species through the stratigraphic sequence or to refute the morphological stasis in N. arquinotensis. Stasis among Antarctic Eocene vertebrates is also recorded among Eocene penguins. The "Plus ça change" model indicate that morphological stasis and punctuated equilibrium were detected as the usual responses to widely fluctuating physical environments such as those characteristic of temperate regions and shallow waters. This model fits well with inferences on Antarctic paleoclimate and paleogeography and the land fossil record.
Eocene High-Latitude Terrestrial Vertebrates from Antarctica as Biogeographic Evidence
Publicación Electrónica de la Asociación Paleontológica Argentina, 1998
A BSTRACT. A moderately di verse terrestrial biota is known from the Eocene-?early Oligocene La Meseta Formation, Seymour Island, Antarctic Peninsula. The La Meseta Formation fills an incised valley and comprises sediments that represent deltaic, estuarine and very shallow marine environments. Forests of both deciduous and evergreen trees were dominated by Nothofagus, podocarps, and araucarian conifers. The La Meseta paleoflora is distinctive in having a predominance of Antarctic taxa; this suggests a seasonal, cold-temperate, rainy c1imate and a latitudinal gradient. Among the terrestrial vertebrates, there are at least nine rnammal taxa, predominantly tiny marsupial s (mostly endemic and new genera). The presence of these marsupials suggests the existence of some form of isolating barrier (c1imatic and/or geographic), which must have allowed development of this endemic fauna. Cornparisons with faunas assigned to the Itaboraian (late Paleocene), Riochican (late Paleocene), Casamayoran (early Eocene), and Mustcrsan (tentatively assigned to the middle Eocene) ages of Patagonia were made. The assemblage of terrestrial vertebrates of the La Meseta Formation is unusual in the dominance of several endemic forms. The occurrence of protodidelphid and derorhynine marsupials, that had become extinct elsewhere in the Eocene of South America, on Seymour Island also indicates that isolation may have allowed extended survival ofthese taxa in theEocene of Antarctica. The nature, distribution, and composition ofthe La Meseta fauna firmly suggest a latitudinal differentiation in the middle Eocene. Paleogeographic evidence suggests that the terrestrial mammals of the La Meseta Formation probably lived under crepuscular and even extended noctumal conditions (assuming that the angle of the earth's spin axis was relatively the same as it is now) during part of the year. RESUMEN.