Inner ear biomechanics reveals a Late Triassic origin for mammalian endothermy.

Endothermy underpins the ecological dominance of mammals and birds in diverse environmental settings. However, it is unclear when this crucial feature emerged during mammalian evolutionary history, as most of the fossil evidence is ambiguous. Here we show that this key evolutionary transition can be investigated using the morphology of the endolymph-filled semicircular ducts of the inner ear, which monitor head rotations and are essential for motor coordination, navigation and spatial awareness.

Living fast in the Triassic: New data on life history in Lystrosaurus (Therapsida: Dicynodontia) from northeastern Pangea.

Lystrosaurus was one of the few tetrapods to survive the Permo-Triassic mass extinction, the most profound biotic crisis in Earth's history. The wide paleolatitudinal range and high abundance of Lystrosaurus during the Early Triassic provide a unique opportunity to investigate changes in growth dynamics and longevity following the mass extinction, yet most studies have focused only on species that lived in the southern hemisphere. Here, we present the long bone histology from twenty Lystrosaurus skeletal elements spanning a range of sizes that were collected in the Jiucaiyuan Formation of northwestern China.