Evolutionary origin of the turtle skull

摘要: Transitional fossils informing the origin of turtles are among most sought-after discoveries in palaeontology. Despite strong genomic evidence indicating that evolved from within diapsid radiation (which includes all other living reptiles), inferred transformation between an ancestral turtle with open, skull to closed, anapsid condition modern remains elusive. Here we use high-resolution computed tomography and a novel character/taxon matrix study Eunotosaurus africanus, 260-million-year-old fossil reptile Karoo Basin South Africa, whose distinctive postcranial skeleton shares many unique features shelled body plan turtles. Scepticism regarding status as earliest stem arises possibility these shell-related products evolutionary convergence. Our phylogenetic analyses indicate cranial support for critical transitional form evolution, thus fortifying 40-million-year extension moving ecological context its back onto land. Furthermore, find unexpected is process becoming secondarily anapsid. This important because categorizing based on number openings complex dermal bone covering adductor chamber has long held sway amniote systematics, still represents common organizational scheme teaching history group. These allow us articulate detailed testable hypothesis fenestral closure along stem. results suggest crucially link chain will eventually lead consilience paving way synthetic studies evolution development.