Tortoises and turtles from Huayquerías del Este (late Miocene-early Pliocene), Mendoza, Argentina.

We report new occurrences of Testudinidae and Chelidae from 11 different fossil sites in the Huayquerías and Tunuyán formations (late Miocene-Pliocene) in the Huayquerías del Este, Mendoza, Argentina. A total of 36 specimens were collected, representing at least three taxa from two different clades: 80.6% Testudinidae and 19.4% Chelidae. Testudinids are present throughout the stratigraphic succession, in alluvial, fluvial, and interdune sedimentary environments, represented by dorsal and plastron carapace plates, with some remains of the appendicular skeleton. A complete articulated plastron with some peripheral plates of the carapace was also recognized and is assigned to the extant species Chelonoidis chilensis, representing the oldest record for this taxon (late Miocene, Messinian). Another possible morphotype was recognized in the form of a large scapular girdle and femur that likely corresponded to an individual with a dorsal carapace of about 80 cm. This assemblage of small and large tortoise species is recognized for first time in the Messinian Age/Stage of Mendoza. Chelids are mostly restricted to fluvial deposits in the upper part of the Huayquerías Formation, except for two specimens which appear in the lower part. One specimen is represented by a right half plastron of an indeterminate Chelidae species which could correspond to a carapace of up to 24 cm in length with plastral lobes narrower than those observed in Phrynops species. Another specimen is characterized by a large costovertebral tunnel in the carapace, peripheral plates of the posterior margin of the carapace with ornamentation of fine grooves forming irregular polygons.

A new giant titanosaur sheds light on body mass evolution among sauropod dinosaurs.

Titanosauria was the most diverse and successful lineage of sauropod dinosaurs. This clade had its major radiation during the middle Early Cretaceous and survived up to the end of that period. Among sauropods, this lineage has the most disparate values of body mass, including the smallest and largest sauropods known. Although recent findings have improved our knowledge on giant titanosaur anatomy, there are still many unknown aspects about their evolution, especially for the most gigantic forms and the evolution of body mass in this clade. Here we describe a new giant titanosaur, which represents the largest species described so far and one of the most complete titanosaurs. Its inclusion in an extended phylogenetic analysis and the optimization of body mass reveals the presence of an endemic clade of giant titanosaurs inhabited Patagonia between the Albian and the Santonian. This clade includes most of the giant species of titanosaurs and represents the major increase in body mass in the history of Titanosauria.

A new primitive Neornithischian dinosaur from the Jurassic of Patagonia with gut contents.

We describe a new species of an ornithischian dinosaur, Isaberrysaura mollensis gen. et sp. nov. The specimen, consisting in an almost complete skull and incomplete postcranium was collected from the marine-deltaic deposits of the Los Molles Formation (Toarcian-Bajocian), being the first reported dinosaur for this unit, one of the oldest from Neuquén Basin, and the first neornithischian dinosaur known from the Jurassic of South America. Despite showing a general stegosaurian appearance, the extensive phylogenetic analysis carried out depicts Isaberrysaura mollensis gen. et sp. nov. as a basal ornithopod, suggesting that both Thyreophora and neornithischians could have achieved significant convergent features. The specimen was preserved articulated and with some of its gut content place in the middle-posterior part of the thoracic cavity. Such stomach content was identified as seeds, most of them belonging to the Cycadales group. This finding reveals a possible and unexpected role of this ornithischian species as seed-dispersal agent.

Cretaceous small scavengers: feeding traces in tetrapod bones from Patagonia, Argentina.

Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem.