Sergio Nestor Santillana

Instituto Antártico Argentino | IAA · Coordinación Científica

New ichthyosaur remains from the Upper Jurassic of Antarctica, recovered from the Ameghino (=Nordenskjöld) Formation are described. These three new specimens represent the first unambiguous records of ichthyosaurs in this continent. Based on the morphology of the humerus, we refer one of the specimens to Ophthalmosauridae, the dominant ichthyosaur...

An articulated wing belonging to Palaeeudyptes gunnari containing mineralized skin was found in Lutetian (middle Eocene) sediments from Seymour Island, Antarctica. It shows the connective tissues, morphology and density of the feather follicles, and a groove pattern left by the feather calami resting on the skin. Analysis of the preserved surfaces...

Los registros de ictiosaurios hallados en Antártida son escasos, encontrándose únicamente tres referencias en la literatura. Las dos primeras mencionan la presencia de una mandíbula de ictiosaurio hallada en las inmediaciones de Longing Gap, sin figurar ni describir el material. El reporte más reciente está basado en el molde de un diente parcialme...

The Paleocene (66-56 Ma) was a critical time interval for understanding the geological history in high palaeolatitudes after the end of Cretaceous event (recovery from mass extinction, palaeoclimate, global sea level changes, among others). The sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from thi...

Dinoflagellate cyst assemblages recovered from the La Meseta Formation cropping out in Seymour Island, Antarctic Peninsula, are studied herein and their distribution is compared with the biostratigraphic scheme available for the Palaeogene of the Southern Ocean and other high-latitude regions. In this way, the La Meseta Formation is dated as middle...

A new Anseriformes, Conflicto antarcticus gen. et sp. nov., represented by associated bones of a single individual, from the early Palaeocene of Antarctica is described. The new taxon is unlike any other known member of the order. Conflicto antarcticus is a medium-sized (2 kg) stem anseriform. The forelimb and pectoral girdle bones suggest that it...

Aristonectines show a highly derived morphology among elasmosaurid plesiosaurs, including some species with large body size. A new postcranial skeleton is described from the uppermost Maastrichtian levels of the López de Bertodano Formation, Seymour Island (= Marambio), Antarctica, being referred to as cf. Aristonectes sp; the most striking feature...

A new Anseriformes, Conflicto antarcticus gen. et sp. nov., represented by associated bones of a single individual, from the early Palaeocene of Antarctica is described. The new taxon is unlike any other known member of the order. Conflicto antarcticus is a medium-sized (2 kg) stem anseriform. The forelimb and pectoral girdle bones suggest that it...

Elasmosaurids are a monophyletic group of cosmopolitan plesiosaurs with extremely long necks. Although abundant elasmosaurid material has been collected from the Upper Cretaceous of Antarctica, skull material is extremely rare. Here, new elasmosaurid cranial material from the lower Maastrichtian levels of the Cape Lamb Member (Snow Hill Island Form...

Los registros de asteroideos fósiles son escasos debido a que las placas del esqueleto están unidas por tejido conectivo y fibras musculares que se desintegran muy rápidamente después de la muerte de los individuos (Gale y Villier, 2013). En el caso que se preserven, estos depósitos se dividen de acuerdo a Brett et al. (1997) en dos grupos discreto...

O’Gorman, J.P., Panzeri, K.M., Fernández, M.S., Santillana, S., Moly, J.J. & Reguero, M. XX.XX.2017. A new elasmosaurid from the upper Maastrichtian López de Bertodano Formation: new data on weddellonectian diversity. Alcheringa xx, xxx–xxx. ISSN 0311-5518. Elasmosaurids are one of the most frequently recorded marine reptiles from the Weddellian Pr...

Here we describe a new terrestrial mammal from the Eocene of Seymour Island (Isla Marambio) represented by a lower left third molar and assigned to a new species of Sparnotheriodontidae, an ungulate family with a broad palaeobiogeographical distribution in South America. The specimen was found in the Cucullaea I allomember of the La Meseta Formatio...

Nowadays, notothenioids are the teleostean group that dominates marine Antarctic waters. However, during the Mesozoic a diverse ichthyofauna inhabited the sea that surrounded Antarctic. We present the preliminary results of the last two Argentinian Antarctic field expedition to the Late Jurassic of Antactic Peninsula (Longing Gape) and Cretaceous-P...

A small humerus from Eocene levels of Seymour Island, Antarctica is assigned here to Aprosdokitos mikrotero sp. and gen. nov. (Aves, Sphenisciformes), based predominantly on its small size. An ontogenetic series based on Pygoscelis antartica was established for comparative purposes, and evaluation of pathological conditions was also carried out in...

Conifer fossil woods represent 54% of an assemblage of 116 specimens collected from sediments of the Sobral Formation in Seymour (Marambio) Island, Western Antarctica. These woods are anatomically described in detail and assigned to seven fossil-species of the following fossil-genera: Agathoxylon (Araucariaceae), Podocarpoxylon, Phyllocladoxylon, P...

During December 2015 / February 2016, within the activities of the ―Vertebrate Paleontology of the James Ross Basin, Antarctic Peninsula‖ project of the Instituto Antártico Argentino, principal fossiliferous localities of Marambio (=Seymour) Island, northeast Antarctic Peninsula (marine late Cretaceous, K-Pg and Paleogene outcrops), and Cape Longin...

Abstract. Basal fully aquatic whales, the basilosaurids, are worldwide known from Bartonian–Priabonian localities, indicating that this group was widely distributed during the late middle Eocene. In the Northern Hemisphere, fossils of basilosaurids are abundant, while records in the Southern Hemisphere are scarce and, in some cases (i.e. Antarctica...

Fossil woods from Paleocene sediments of the Cross Valley Formation (Seymour Island, Antarctic Peninsula) are anatomically studied in detail. We collected 64 samples represented almost exclusively by conifers (95%). Only three samples of not determinable angiosperm fossil wood were found. Preservation of the samples is often poor and 52% of the sam...

The biogeographic hypothesis more accepted today is that Antarctica (West Antarctica) and southern South America (Magellan region, Patagonia) were connected by a long and narrow causeway (Weddellian Isthmus) between the Antarctic Peninsula and South America since the Late Cretaceous (Campanian) until the Early Paleogene allowing terrestrial vertebr...

The occurrence of a large gastrolith set associated with a specimen referred to Aristonectes sp. is reported here for the first time. The specimen MLP 89-III-3-1 comes from Seymour Island (Is. Marambio), Antarctic Peninsula, López de Bertodano Formation (upper Maastrichtian). The gastrolith cluster is composed of 793 elements (534 in their presumed...

The La Meseta Formation crops out in Seymour/Marambio Island, Weddell Sea, northeast of the Antarctic Peninsula and contains one of the world's most diverse assemblages of Weddellian marine/coastal vertebrates of Early Eocene (Ypresian) age. The La Meseta Formation is composed of poorly consolidated, marine sandstones and siltstones which were depo...

a b s t r a c t A new ornithopod dinosaur from Antarctica, Trinisaura santamartaensis n. gen. et n. sp. is diagnosed by a unique combination of characters that includes a scapula with a spike-like acromial process with a strong and sharp lateral crest and longer than other ornithopods, a humerus with a rudimentary deltopectoral crest represented as...

The history of dispersal and evolution of the Antarctic land mammal faunas is closely related to the fate of the land bridge between South America and the Antarctic Peninsula and in the end to its interruption during the Paleogene. The greatest insight can be obtained from taxa that were the most unlikely to have rafted, swum, or flown across expan...

The La Meseta Formation crops out in Seymour/Marambio Island, Weddell Sea, northeast of the Antarctic Peninsula and contains one of the world's most diverse assemblages of Weddellian marine/coastal verte-brates of Early Eocene (Ypresian) age. The La Meseta Formation is composed of poorly consolidated, marine sandstones and siltstones which were dep...

The La Meseta Formation crops out in Seymour/Marambio Island, Weddell Sea, northeast of the Antarctic Peninsula and contains one of the world's most diverse assemblages of Weddellian marine/coastal vertebrates of Early Eocene (Ypresian) age. The La Meseta Formation is composed of poorly consolidated, marine sandstones and siltstones which were depo...

The unconformity bounded Paleocene Sobral and Cross Valley formations represent part of the uppermost infill of the James Ross Basin of northeastern Antarctic Peninsula. Both units have been subdivided into allomembers since they also present internal unconformities. The Sobral Formation represents silicoclastic sedimentation on a marine shelf duri...

The unconformity bounded Paleocene Sobral and Cross Valley formations represent part of the uppermost infill of the James Ross Basin of northeastern Antarctic Peninsula. Both units have been subdivided into allomembers since they also present internal unconformities. The Sobral Formation represents silicoclastic sedimentation on a marine shelf duri...

La secuencia paleógena de la isla Marambio/Seymour (Fig. 1) en la Cuenca de James Ross, Antártida, contiene una fauna terrestre del Eoceno (Formación La Meseta) que documenta las características bióticas propias de un aislamiento geográfico y previas al establecimiento de la cubierta de hielo permanente en el límite Eoceno/Oligoceno. Los mamíferos...

We 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 age...

Araucaria antarctica Césari et al. is an illegitimate name because it is a later homonym of Araucaria antarctica Gee (fossil Araucariaceae). Hence, a new specific epithet, fibrosa, is proposed to accommodate the species described more recently.

Sedimentological and paleontological study of the Man Aike Formation at the Estancia 25 de Mayo, SW of Santa Cruz Province, Argentina, represents the evolution of an incised valley from fluvial to marine environment during the late middle Eocene. At the base of the unit there is an unconformity that corresponds to fluvial channels which cut down in...

Palaeostress inferred from brittle mesostructures in Seymour (Marambio) Island indicates a Cenozoic to Recent origin for an extensional stress field, with only local compressional stress states. Minimum horizontal stress (σ3) orientations are scattered about two main NE–SW and NW–SE modes suggesting that two stress sources have been responsible for...

We describe and comment on an isolated upper molar belonging to Woodburnodon casei gen. et sp. nov. (Mammalia, Marsupialia, Microbiotheria, Woodburnodontidae fam. nov.), from the Eocene of the La Meseta Fm (TELM 5 or Cucullaea I Member), Marambio (Seymour) Island, Antarctic Peninsula. With a body mass estimated between 900 to 1,300 g (depending on...

This study analyzes the palynological organic matter behavior throughout the Cretaceous- Paleogene boundary in Marambio (Seymour) Island, Antarctic Peninsula. The boundary is located in the upper part of the López de Bertodano Formation, coinciding with a widespread glauconitic level. Fifteen samples were analyzed and associated with four palynofac...

Modern penguins are typically small to medium-sized birds, and nearly all known modern specimens are smaller than the most archaic Paleogene relatives. Here we report an incomplete humerus, associated femur and tibiatarsus of a new spheniscid, Crossvallia unienwillia nov. gen. and sp., from the Late Paleocene (~55 million years, Myr) of Antarctica,...

UBA). Cerrito 1248, Buenos Aires (1010), Argentina. RESUMEN. En el sureste del lago Viedma afloran sedimentitas del Cretácico superior y Paleógeno de la cuenca Austral. En el perfil de Barrancas Blancas se describen 28 m de areniscas y fangolitas amarillentas correspondientes al Miembro La Asunción de la Formación Anita que son cubiertas en forma c...

Late Cretaceous and Paleogene sedimentary rocks of the Austral Basin crop out on the south-eastern margin of Lake Viedma. In the Barrancas Blancas section, 28 m of yellowish sandstone and mudstone of the La Asunción Member of the Anita Formation are transitionally covered by 390 m of greyish sandstone and mudstone of the Cerro Fortaleza Formation....

The Eocene of Seymour Island contains the only association of Cenozoic plants and land vertebrates known from anywhere in Antarctica and lies at about latitude 63° south. The late Early to latest Eocene La Meseta Formation fills an incised valley and comprises sediments representing deltaic, estuarine and very shallow marine environments. The Paleo...

The Eocene La Meseta Formation is the youngest exposed unit of the back-arc James Ross Basin, Antarctic Peninsula, cropping out in Seymour (Marambio) Island. The formation comprises 720 m of clastic sedimentary rocks of deltaic, estuarine and shallow marine origin. It was subdivided into six unconformity-based units (Valle de Las Focas, Acantilados...

A fragment of an araucarian ovuliferous cone, araucarian leaves and podocarpaceous wood are described from Upper Cretaceous strata exposed at Cape Lamb, Vega Island, Antarctica. The wood fragment and the reproductive cone come from the middle part of the early Maastrichtian K2 unit whereas the leaves referred to a new species, Araucaria antarctica,...

The endolithic bioerosion structures described herein were found on the external surface of right valves of Ostrea antarctica Zinsmeister from the lower section of the Eocene La Meseta Formation, on Seymour Island, Antarctica. The traces are referred to Feldmannia cavernosa new ichnogenus and new ichnospecies and are the first evidence of boring br...

Department of Earth Sciences, University of California, Riverside, California 92521Duck-billed dinosaurs or hadrosaurs are a very common family ofdinosaurs in the Late Cretaceous of North America and Eurasia withrare occurrences in South America. Here, we report the first hadrosaurrecovered in Antarctica from sandstones of late Maastrichtian age, Ve...

New elements of the La Meseta Formation megaflora are described. This unit crops out on the northern third of Marambio (Seymour) Island, Antarctica. Fossil leaves were collected from the middle part of this formation, dated as middle Eocene. Although the fossils are not well preserved, we identified elements assignable to the following families: No...

At Bahía Sloggett, the Punta Cactus Formation (yellowish and reddish fanglomerate and conglomerate, 125 m) and the Sloggett Formation (95 m) are exposed in a small tectonic window below a thrust block of the Lemaire Formation (Jurassic). The Sloggett Formation presents a complex arrangement of lenticular beds consisting of two members and four faci...

La Meseta Formation is a discontinuity bounded sedimentary unit which crops out on Marambio (Seymour) and Cockburn islands, approximately 100 km SE of the northern tip of the Antarctic Peninsula. The base of this unit is a diachronous surface which intersects all other older units of the island. Along this surface the hiatus increases towards the W...

A new xanthid crab, Tumidocarcinusfoersteri n. sp. is described from the La Meseta Formation on Seymour Island, Antarctica. The fossils were obtained from the Allomember Submeseta of Late Eocene age. As other representatives of the genus Tumidocarcinus were only known from New Zealand and Australia, this finding provides new insights on the palaeob...

Se describen los primeros restos fósiles de tortugas Dermochelyidae en la Península Antartica. Los mismos proceden de afloramientos de la Formación La Meseta (Eoceno) en tres localidades de la Isla Marambio (Seymour). Los materiales fósiles consisten en placas aisladas y un pequeño fragmento de la coraza, de naturaleza epitecal, correspondientes a...

Middle Eocene land mammals from La Meseta Formation, Seymour (Marambio) Island are reviewed. A taxonomically diverse fossil land-vertebrate assemblage with small and medium-size mammals has been recovered from four localities. The depositional setting is shallow marine and most of the mammal-bearing beds are in reworked, moderate to high energy sub...

Se determinan maderas fósiles terciarías provenientes de la Formación La Meseta, en la isla Seymour (64° 1.5' S.. 56°40' W.). La mega/lora se compone de cinco coniferas: Araucarioxylon novaezelandae Stopes, A. pseudoparenchymatosum Goihan, A. seymourense sp. nov., Cupressinoxylon seymourense sp. nov,, Phyllocladoxylon antarcücum Gytnan y la dicotil...

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...

We describe an isolated upper molar belonging to the largest known microbiotheriid marsupial. It size, as well as its derived features in the molar morphology suggests it belongs to a new genus and species (still unnamed). It is not clear from its known morphology the phylogenetic affinities of this taxon. It adds a second microbiotheriid to the An...