Look, #FossilFriday is smiling at you!
This fossil is Diadectes phaseolinus, and it lived in the Early Permian, about 280 million years ago. The anthracosaurs that gave rise to the amniotes—true land animals with watertight eggs—probably looked something like Diadectes. Diadectes shows the general form of early amniote relatives: well developed limbs clearly capable of terrestrial locomotion, but a posture that is sprawling, not erect, like that of many later amniotes. What Diadectes ate is unknown, but it had complex, molarlike teeth and may have been a plant-eater.
This fossil is located in the Museum’s Hall of Vertebrate Origins.