Abstract The Natural History Museum (NHMUK) fossil reptile collections contain a set of specimens sent to Arthur Smith Woodward in 1908 by the Argentinian palaeontologist, Florentino Ameghino. This collection includes a skull and other material of Cricosaurus , a metriorhynchid thalattosuchian (or ‘sea crocodile’), a group of marine crocodylomorphs that existed from at least the Middle Jurassic to the Early Cretaceous. Handwritten labels in Spanish, probably by Ameghino, and notes in English signed by Smith Woodward are still with the specimens. Using Ameghino and Smith Woodward’s correspondence to investigate the history of the specimens, we have determined that they came from the Vaca Muerta Formation of the Neuquén Basin in Patagonia, they were in the fossil collection of the Museo Nacional, Buenos Aires (MNBA) and that Ameghino loaned them to Smith Woodward for a study that was never published. Therefore, they will be returned to Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Buenos Aires. These fossils, although not the most impressive, are probably the first metriorhynchid material collected in South America.

Abstract The fossil record of terrestrial vertebrates from the Late Cretaceous of Antarctica is currently composed of non-avian and avian dinosaurs from the marine sediments of the James Ross Basin, Antarctic Peninsula (West Antarctica). Although two dinosaurian formational assemblages (Late Campanian/Early Maastrichtian and Late Maastrichtian) are known, the record is still scattered, and evolutionary scenarios are tentative. Ten non-avian dinosaurs have been reported from Coniacian to Maastrichtian deposits, along with possible sauropod footprints of Early Maastrichtian age from Snow Hill Island. Five avian dinosaurs have been recorded or described exclusively from the Maastrichtian. The presence of an advanced titanosaur with characteristic procoelous mid-caudal vertebrae in Snow Hill Island Formation at Santa Marta Cove implies that the group achieved a global distribution by the Late Campanian. The Late Campanian/Early Maastrichtian non-avian dinosaur (ankylosaurs, ornithopods and dromaeosaurid theropods) clades probably attained a near-cosmopolitan distribution before the Late Cretaceous, and some aspects of this hallmark ‘Gondwanan’ fauna may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. Antarctic Late Cretaceous avian dinosaurs are rare. They are restricted to the Maastrichtian and consist of a cariamid?, gaviids, a charadriiform and the basal Anseriformes Vegavis , and provide the first strong evidence for a basal radiation of birds known to exist in the Cretaceous.

ABSTRACT This chapter summarizes the abundant marine paleobiological markers recorded in the Vaca Muerta Formation illustrating their richness, biodiversity, and application for age dating and paleobiogeographical global correlation. The markers described include ammonites, calcareous nannofossils, calcisphaeres (calcareous dinoflagellate cysts), calpionellids, coprolites, dinoflagellates, radiolarians, saccocomid microcrinoids, and trace fossils. Traditionally, the ammonites have been the best known and most relevant macroinvertebrate fossil group. Nevertheless, in the past decade, the exploration of the Vaca Muerta unconventional play has boosted the research on the micropaleontology of the area determining an extensive growth in knowledge and reported here.