Abstract The Snow Hill Island Formation (SHIF; late Campanian – early Maastrichtian) crops out in the northeast of the Antarctic Peninsula and constitutes the basal part of the late Campanian-early Maastrichtian sedimentary succession of the James Ross Basin (NG Sequence). Its major exposures occur at the James Ross and Vega islands. Several fossil-bearing localities have been identified in the SHIF providing a valuable fauna of invertebrates and vertebrates, and flora. Our study focuses on the vertebrate fauna recovered at Gamma and Cape Lamb members of the SHIF. The marine vertebrate assemblages include chondrichthyans, actinopterygians, and marine reptiles (elasmosaurid plesiosaurs and mosasaurs). A diverse terrestrial vertebrate assemblage has been reported being characterized by dinosaurs (sauropod, elasmarian ornithopods, nodosaurid ankylosaur, and a paravian theropod), pterosaurs and birds. Most SHIF dinosaurs share close affinities with penecontemporaneous taxa from southern South America, indicating that at least some continental vertebrates could disperse between southern South America and Antarctica during the Late Cretaceous. The Snow Hill Island Formation provides the most diverse Late Cretaceous marine and continental faunas from Antarctica. The present study summarizes previous and new vertebrate findings with the best actualized stratigraphical framework, providing a more complete fauna association and analyzing further perspectives.

Abstract Geological studies in the northern sector of the Chaco foreland Basin, Bolivia, yielded new fossils coming from late Oligocene-late Miocene of the Petaca Formation. Few fossil mammals were known from the Subandean Region of Bolivia. We report a partially complete mandible of a hegetotheriid Hegetotheriinae (Notoungulata, Typotheria) from Abapó (Río Grande River). The specimen (YPFB-LIT-PAL-005) is very close in size and dental morphology to the late Oligocene (Deseadan South American Land Mammal Age, SALMA) — Santacrucian (early Miocene) Prohegetotherium schiaffinoi (Kraglievich 1932) from Fray Bentos (Uruguay and Argentina), Salla (Bolivia), Divisadero Largo-Potrerillos and Quebrada Fiera (Argentina). However, mandibular characteristics, as the shape with a marked change in height along its length, increasing towards the back, a prominent masseteric crest, a deep mandibular groove, and a remarkable thickening of the ventral rim of the mandible, indicate differences between this specimen and Prohegetotherium schiaffinoi and the other Hegetotheriinae. The affinity of YPFB-LIT-PAL-005 with P. schiaffinoi suggests a late Oligocene to early Miocene for the upper bearing horizon of the Petaca Formation (in Abapó), an older age than previously assigned to the top of this unit (late Miocene), and confirms the taxon distribution between ∼ 36 ° to ∼ 17 ° south latitude.

Roca Formation is a stratigraphic succession of marine and continental sediments that belongs to Malargüe Group, which was deposited from the Late Campanian to the Danian in the Neuquén Basin, western Argentina. Fossil vertebrates recovered at different outcroppings of this lithostratigraphic unit correspond to marine taxa. The turtle material studied here was collected from the lower section of Roca Formation (Maastrichtian?-Danian) in northeastern Lago Pelegrini (38º 40' 06''S, 67º 52' 02'' O), Rio Negro Province. Remains of carapace and plastron of continental turtles were assigned to indeterminate chelid pleurodires and to Yaminuechelys cf. maior (Staesche, 1929). This record of chelid turtles in Roca Formation confirms the existence of marine paleoenvironments with continental influence and represents the first record of Danian continental vertebrates in the Neuquén Basin.

La Formación Roca integra la sucesión estratigráfica de sedimentitas marinas y continentales del Grupo Malargüe, depositadas durante el intervalo Campaniano tardío-Daniano en la Cuenca Neuquina, centro-oeste de Argentina. Los vertebrados fósiles recuperados en diferentes localidades donde esta unidad litoestratigráfica aflora corresponden a taxones marinos. El material de tortugas estudiado en este trabajo proviene de la sección inferior de la Formación Roca (Maastrichtiano?-Daniano), del sector NE del Lago Pellegrini (38º 40' 06''S, 67º 52' 02'' O), provincia de Río Negro. Se reconocen fragmentos de caparazón dorsal y plastrón de tortugas continentales Pleurodira Chelidae, algunos indeterminados, y otros asignados a Yaminuechelys cf. maior (Staesche, 1929). La presencia de quélidos en niveles de la Formación Roca está evidenciando la existencia de ambientes marinos con una clara influencia continental y constituye el primer registro de vertebrados continentales para el Daniano en la Cuenca Neuquina.

Eocaiman Simpson represents one of the few known taxa of alligatorids from the Paleogene of South America. This genus is accurately recorded in Patagonia in the late Eocene, with E. cavernensis Simpson, and in the middle Miocene in the area of La Venta, Colombia, with Eocaiman sp. In this paper a new species, Eocaiman palaeocenicus sp. nov., from the upper levels of the Salamanca Formation (Lower Paleocene) is described on the basis of new remains recently found in the coastal zone of the province of Chubut, Argentina. The Alligatoridae are poorly represented in the Paleogene in South America and they have not been recorded in the upper Cretaceous in this continent. However, the presence of E. palaeocenicus sp. nov. in the Lower Paleocene of Patagonia supports the hypothesis of an early diversification of Caimaninae in South America.

Eocaiman Simpson representa uno de los pocos taxones de aligatóridos caimaninos conocidos del Paleógeno de América del Sur. Este género se encuentra registrado con seguridad en Patagonia en el Eoceno tardío, con E. cavernensis Simpson, y en el Mioceno Medio en el área de La Venta, Colombia, con Eocaiman sp. En este trabajo se describe una nueva especie Eocaiman palaeocenicus sp. nov., proveniente de los niveles superiores de la Formación Salamanca (Paleoceno Inferior), sobre la base de restos recuperados recientemente en la zona costera de la provincia del Chubut, Argentina. Los Alligatoridae están pobremente representados en el Paleógeno en América del Sur y hasta el momento no han sido registrados en rocas del Cretácico tardío en este continente. No obstante, la presencia de E. palaeocenicus sp. nov. en el Paleoceno Inferior en Patagonia da sustento a la hipótesis de una diversificación temprana de los Caimaninae en América del Sur.