FROM FOSSIL BONE CELLS TO THE LARGEST PALEOGENE TROPICAL TURTLE

Here I present the results of seven years of research on Mesozoic and Cenozoic fossil turtles from the Neotropics, including their phylogenetic, paleoecological, and bone preservation implications. Turtles from the Early Cretaceous (Valanginian) of Zapatoca, Colombia, constitute the most basal pleurodires of tropical South America including platychelyids, as well as basal eucryptodires, and potentially the earliest record of podocnemidoids, group that includes the extant side-necked turtles of South America, Africa, and Madagascar. Early Cretaceous (Barremian-Aptian) turtles from Villa de Leyva, Colombia represent the earliest record of protostegids, the giant marine Cretaceous turtles. Middle-Late Paleocene turtles from Cerrejón Coal Mine show one of the most diverse Cenozoic fossil turtle fauna in tropical South America, including closer relatives to the extant freshwater genus Podocnemis, giant podocnemidid turtles as big as a smart car, and one species of bothremydid with one of the most circular shell in the fossil record of turtles. Early Miocene turtles from the Panama Canal Basin, represent the first evidence of interaction between North American cryptodires and South American pleurodires much earlier to the final closure of the Isthmus of Panama. All these discoveries show a much higher paleodiversity of tropical turtles compared to the present, and their inclusion in phylogenetic analyses have helped to resolve problematic clades, and also in calibration of molecular clocks. Bone histology and demineralization of bone have shown an excellent preservation of bone cells, particularly osteocytes, indicating that the preservation of cells is independent of environmental conditions and age, opening the possibility for future molecular paleontology studies on