Recent advances in the fossil record, anatomy, and evolutionary history of South American turtles allow a thorough analysis of their changes in diversity, and to identify several major extinction events. With the onset of the breakup of Pangea in the Middle Jurassic, turtles begin to diversify, giving rise to the main South American turtle clades some of which survive until present. The first peak of diversity was achieved in the Early Cretaceous. A first extinction event is recognized at the end of the Early Cretaceous, affecting mainly the pelomedusoids in northern latitudes and coinciding with the final separation of South America from Africa. The K–Pg boundary mass extinction affected deeply the thriving turtles in South America by reducing their diversity in half. Reduction of diversity continued on the aftermath of the K–Pg extinction, roughly until the middle Eocene and the final isolation of South America from Antarctica. In this “new” continent, the diversity of the surviving turtles continued to decrease, until an injection of biodiversity from Africa, with the arrival of tortoises, which helped to recover the diversity levels. The Andean uplift in Late Oligocene–Early Miocene and the associated climate and habitat changes posed new problems for the turtles of the continent. New injections of biodiversity took place at the end of the Neogene with the Great American Biotic Interchange, as novel clades reached South America from the North. The modern biodiversity of South American turtles took its final shape only during the last million years.

Titanosauria is a clade of sauropod dinosaurs that includes some of the largest terrestrial animals ever recorded. An outstanding feature of some species of this group is the presence of osteoderms, which are bony deposits on the skin that form scales, plates or other structures. Only six osteoderms have been identified from Brazil. Herein, we describe the first titanosaurian osteoderm from the Potiguar Basin (Early–Late Cretaceous) and discuss Brazilian titanosaur osteoderm diversity, their taxonomy and the functional implications. The specimen (UFRJ-DG 549-R) is bilaterally symmetrical and is assigned to the ellipsoid morphotype. The most interesting feature is the large cavities separated by thin trabeculae. This pattern, according to recent interpretations, suggests that titanosaur osteoderms functioned as a source of calcium. However, the function(s) of titanosaur osteoderms remain(s) open to debate. Compared with the other reported osteoderms from Brazil, the Potiguar osteoderm shows more similarities with an osteoderm of Ibirá (Bauru Group, Turonian–Santonian) than with material collected from the São Luís Basin (Albian–Cenomanian) despite their greater geographical and temporal proximity. The Potiguar and Ibirá osteoderms are of the ellipsoid morphotype, with no cingulum and several pits on the external surface. More findings are necessary to clarify whether the Potiguar material represents a different armored titanosaurian species in northeastern Brazil.

Horn sharks (Elasmobranchii: Heterodontus Blainville) correspond to a genus of chondrichthyan fishes, mostly distributed in warmtemperate to tropical regions of the Pacific and Indian Oceans. The fossil record shows that, in contrast to its current distribution, horn sharks were widely distributed both in the eastern Pacific and western Atlantic during the Neogene, being subsequently extirpated from some of these areas. In this contribution, we describe new Heterodontus teeth from three Pliocene localities in the Coquimbo Region, in north-central Chile, and make an extensive revision of the fossil record of the genus in the Americas, in order to specify the timing of their extirpation in the southeastern Pacific and discuss the possible causes of this event. The new specimens described herein belong to a species with a Heterodontus francisci type dentition. Our analysis suggest that the removal of horn sharks occurred in the context of a general faunal turnover in the transition from Pliocene to Pleistocene, and that it was probably controlled by an interplay between the oceanographic, tectono-eustatic and ecological changes occurred in the region at that time.

It is not yet known how old parental care in mammals is. One fossil trackway ascribed to Ameghinichnus patagonicus of a mouse-sized primitive mammal from the Middle Jurassic of Patagonia, Argentina, of almost 170 Ma, shows deviation from the usual bilateral symmetry of posture and motion: the left forelimb digits were dragging in the swing phase, and the tail was bent to the right and dragged over the right footprints. However, the footprints are evenly spaced, indicating that the animal was not limping. The opposition of the tail and the forelimb dragging marks could possibly be explained by a heavy load carried on the left side. This hypothesis is supported by experiments on laboratory rats. A plausible load for Ameghinichnus track-maker could be babies riding on a milk-producing mother, as they do in extant opossums and many other mammals. Baby-riding is a missed possible feature of basal mammals, which potentially integrates evolutionary acquisition of profound mammalian features, such as milk-feeding, endothermy, hairs, and limb parasagittalism.