The systematics of the Late Cretaceous non-aristonectine elasmosaurids from Argentinean Patagonia are poorly known as there is no valid species currently recognized. Here a new non-aristonectine elasmosaurid: Kawanectes lafquenianum nov. comb. from the late Campanian—early Maastrichtian Allen Formation is diagnosed. K. lafquenianum is a distinctively small-body sized non-aristonectine elasmosaurid characterized by caudal vertebrae with marked laterally projected parapophyses, presence of pelvic bar, high ratio (∼1.2) between humerus/femur length and a large posterodistal projection of the humerus which bears a posterior accessory articular facet. A phylogenetic analysis recovered K. lafquenianum closely related with Morenosaurus stocki, Vegasaurus molyi, and Aristonectinae, showing the relationships between the elasmosaurids from Patagonia, Western Antarctic, and the Pacific coast of the USA. K. lafquenianum is part of the fauna of the coeval Allen and La Colonia formations that also comprises indeterminate aristonectines and polycotylids. This relatively high diversity plesiosaur fauna includes the three main morphotypes (aristonectines, non-aristonectine elasmosaurids and polycotylids), which is remarkable because the depositational environments of the Allen Formation have been inferred as marginal marine to non-marine environments.

A new incomplete penguin skeleton is described herein. It is assigned to Palaeeudyptes klekowskii Myrcha, Tatur and Del Valle, a giant sphenisciform from the Priabonian Submeseta Formation in Marambio/Seymour Island, Antarctic Peninsula. Also provided is a paleobiological discussion derived from the morphology of this skeleton. A thorough description of muscular origin and insertions, body mass, body length, and diving duration estimations support the hypothesis that the new specimen represents a marine bird with limited swimming skills wighing 40–44 kg and measuring 133.2–143.2 cm long.

Un nuevo e incompleto esqueleto perteneciente a Palaeeudyptes klekowskii Myrcha, Tatur y del Valle, procedente de la Formación Submeseta (Priaboniano) de la Isla Marambio/Seymour, Península Antártica es aquí estudiado. Se brinda además una discusión acerca de sus atributos paleobiológicos a partir de la morfología del esqueleto. Una detallada descripción de los orígenes e inserciones musculares, sumado a las estimaciones de su masa, longitud corporal, y capacidades de buceo, soportan la idea de que el nuevo espécimen correspondió a un ave nadadora de unos 40–44 kg de peso y 133.2–143.2 cm de largo con limitadas capacidades locomotoras bajo el agua.

The purpose of this paper is to provide a taphonomic analysis of the holotype of Crossvallia unienwillia Tambussi, Reguero, Marenssi and Santillana, 2005, in order to improve the knowledge of the vertebrate record of the Cross Valley Formation, a unit exposed in the central area of Marambio (Seymour) Island, Antarctic Peninsula. Analyses of the preservational state of the skeleton assigned to Crossvallia unienwillia offer important data for palaeoenvironmental and depositional reconstructions, key for the understanding of the early evolutionary history of penguins. Different techniques, including petrographic sections, SEM observation, Secondary Electrons Detectors, backscattered electrons detectors, microanalysis for probe of electrons, and X-ray diffraction were applied in order to distinguish biostratinomic from fossil diagenetic damage. Fossil bones of Crossvallia are associated with a typical marine assemblage including shark remains and macroinvertebrates. The hosting mudstones suggest a low-energy environment either below the wave-base or protected from wave action. In any case initial marine conditions changed to other with regular influx of land-derived sedimentary material. Crossvallia unienwillia was a female diver that passed through several molting periods before death. Biostratinomic processes consistent with little transport and rapid burial which would have prevented the action of destructive processes such as weathering and carnivores or scavenging, are inferred. The rapid burial favored the initial preservation of the elements under anoxic conditions. The surficial corrosion, fractures, and the internal filling of the cavities, suggest that destructive processes were only important after final burial during the telodiagenetic stage. The absence of more vertebrate fossil remains in the Cross Valley C Allomember is the result of those destructive processes, whereas on the contrary the original depositional environment appears to have been optimal.

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), doubtful. The presence of basilosaurids in Antarctica was, until now, uncertain because most of the records are based on fragmentary materials that preclude an accurate assignment to known archaeocete taxa. Here we report the findings of mandibles, teeth, and innominate bone remains of basilosaurids recovered from the La Meseta Formation (TELM 4 Lutetian—Bartonian and; TELM 7 Priabonian), in Marambio (Seymour) Island (James Ross Basin, Antarctic Peninsula). These findings confirm the presence of Basilosauridae in the marine realm of Antarctica, increasing our knowledge of the paleobiogeographic distribution of basilosaurids during the middle—late Eocene. In addition, one of these records is among the oldest occurrences of basilosaurids worldwide, indicating a rapid radiation and dispersal of this group since at least the early middle Eocene.

El registro fósil de los basilosáuridos está bien documentado durante el Bartoniano—Priaboniano en varias localidades del mundo, lo cual indica que este grupo estaba ampliamente distribuido durante el Eoceno medio tardío. En el Hemisferio Norte, el registro fósil de este grupo es abundante, a diferencia de lo que ocurre en el Hemisferio Sur donde es escaso y, en algunos casos (i.e., Antártida), dudoso. La presencia de basilosáuridos en Antártida es incierta ya que la mayoría de los registros están basados en materiales fragmentarios, lo cual imposibilita su asignación a algún grupo de arqueocetos. En la presente contribución se describen restos de basilosáuridos correspondientes a mandíbulas, dientes aislados y un hueso pélvico, recuperados de la Formación La Meseta (TELM 4 Lutetiano—Bartoniano; TELM 7 Priaboniano), Isla Marambio (Seymour), (Cuenca James Ross, Península Antártica). Este hallazgo confirma la presencia de Basilosauridae en la Antártida, contribuyendo al conocimiento de la distribución paleobiogeográfica de este grupo durante el Eoceno medio—tardío. Finalmente, uno de estos registros se encuentra entre los basilosáuridos más antiguos conocidos, indicando un rápida radiación y dispersión de este grupo al menos desde el Eoceno medio temprano.

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.

A micropaleontological analysis of foraminifera and palynomorphs obtained from a partial sedimentary section cropping out at Ekelöf Point, eastern James Ross Island, Antarctic Peninsula, is presented. The section, named Ekelöf Coast, includes the lowest levels of the Upper Cretaceous Hamilton Point Member of the Snow Hill Island Formation. Among the foraminifera, 18 benthic taxa including 10 agglutinated and eight calcareous are recognized. Palynomorphs include continental and marine species. The continental assemblage contains 44 spore and pollen species. The marine assemblage consists of 10 peridinioid dinoflagellate cysts species, dominating in number of specimens, and 10 gonyaulacoids. Although the palynomorph assemblage supports a late Campanian age for the section, an earliest Maastrichtian age is not excluded. The paleoenvironmental interpretation based on the distribution of foraminiferal morphogroups indicates an outer shelf-upper bathyal environment in agreement with sedimentological data. The paleoenvironmental inference based on the S/D ratio (sporomorph versus dinoflagellate cysts) and the P/G ratio (peridinioid versus gonyaulacoid cysts) suggest a coastal to inner neritic setting with a continuous continental supply from the continent to the marine environment, evidenced by the slight dominance of the peridionoids over gonyaulacoids cysts. The discrepancy observed between palynological and micropaleontological-sedimentological data may be linked to the development of a narrow continental shelf during the Late Cretaceous. In such continental shelf, terrestrial palynomorphs and peridinoid cysts would quickly run down the slope and would be deposited in the deep marine environment together with gonyaulacoid cysts.

I present a diverse previously unrecorded assemblage of leaves, cuticle, seeds and fruits from early—mid Campanian marine sediments, representing the first well-preserved macrofloristic record found in the Santa Marta Formation (north of James Ross Island, Antarctica). This new flora is diverse and consistent with the presence of forests under temperate and frost free climate; taxa include: a cycad (Zamiaceae), conifers (Araucaria, Araucarites, Brachyphyllum, and Pagiophyllum), several ferns (including Pteridaceae and ?Schizaeaceae) and angiosperms (including ?Cunoniaceae and Lauraceae). This record helps further our understanding of the vegetation of continental areas in the Antarctic Peninsula during the Late Cretaceous.

Presento una diversa asociación previamente no registrada de hojas, semillas y frutos, en sedimentos marinos del Campaniano temprano—medio, representando el primer registro macroflorístico bien preservado en la Formación Santa Marta (norte de la isla James Ross, Antártida). La flora es consistente con la presencia de bosques bajo clima templado libres de heladas, incluyendo: una cycadal (Zamiaceae), coníferas (Araucaria, Araucarites, Brachyphyllum y Pagiophyllum), varios helechos (incluyendo Pteridaceae y ?Schizaeaceae) y angiospermas (incluyendo ?Cunoniaceae y Lauraceae). Este registro incrementa el conocimiento de la vegetación en áreas continentales de la Península Antártica durante el Cretácico Tardío.

Belying previous interpretations on its rarity in southern latitudes, Gaudryceras de Grossouvre is well represented in the Santonian—Campanian of Antarctica. The study of more than 300 specimens from the Santa Marta, Rabot and Snow Hill Island Formations designates five species that characterize four successive stratigraphic intervals: 1) Gaudryceras cf. G. strictum, Santonian, Alpha Member, lower part of the Santa Marta Formation; 2) Gaudryceras santamartense sp. nov., Santonian—early Campanian, Alpha Member, lower mid part of the Santa Marta Formation; 3) Gaudryceras brandyense sp. nov., late early Campanian—?basal mid Campanian, Beta Member, upper part of the Santa Marta Formation; and 4) Gaudryceras cf. G. mite and Gaudryceras rabotense sp. nov., mid Campanian—late Campanian, upper middle part of the Rabot Formation and lower part of the Hamilton Point Member of the Snow Hill Island Formation. There are two differently ornamented neanoconchs characterized by exhibiting dense or sparse strong flares, which are features of taxonomic importance at the specific level. In Antarctica, Gaudryceras is well represented from the Santonian to the mid Campanian, rare in the late Campanian and not known in the Maastrichtian. Such facts strongly contrast with data recorded outside Antarctica, particularly in the North Pacific, where Gaudryceras is well represented up to the late Maastrichtian. A striking biogeographical contrast is apparent for the Antarctic gaudryceratids. That is, while the early Campanian Gaudryceras brandyense sp. nov. and the mid-late Campanian G. rabotense sp. nov. are apparently restricted to Antarctica, the Santonian—early Campanian Antarctic species are very similar or co-specific to widely distributed forms.