History
A 236-Million-Year-Old Bone Disruption Suggests Mammals Gave Birth Much Earlier Than Predicted
Evidence from a Triassic cynodont fossil discovered in Argentina suggests that live birth may have emerged in the mammalian lineage approximately 90 million years earlier than previously thought. Microscopic analysis of the animal's limb bones reveals a 'neonatal line' typically associated with the metabolic stress of birth in placental mammals.