Evolutionary origin of the turtle skull

Cora Rivera

By G. S. Bever, Tyler R. Lyson, Daniel J. Field & Bhart-Anjan S. Bhullar

Transitional fossils informing the origin of turtles are among the most sought-after discoveries in paleontology^{1, 2, 3, 4, 5}. Despite strong genomic evidence indicating that turtles evolved from within the diapsid radiation (which includes all other living reptiles^{6, 7}), evidence of the inferred transformation between an ancestral turtle with an open, diapsid skull to the closed, anapsid condition of modern turtles remains elusive. Here we use high-resolution computed tomography and a novel character/taxon matrix to study the skull of Eunotosaurus africanus, a 260-million-year-old fossil reptile from the Karoo Basin of South Africa, whose distinctive postcranial skeleton shares many unique features with the shelled body plan of turtles^{2, 3, 4}.

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