๐ฆด A 236-Million-Year-Old Fossil Just Pushed Back Mammal Live Birth by 90 Million Years
Researchers studying the cynodont Chiniquodon theotonicus found a neonatal growth line in its fossilized bone โ a microscopic band that only forms at the moment of birth. Published in Frontiers in Mammal Science this week, the study places viviparity in the mammalian lineage 236 million years ago, a full 90 million years earlier than previous fossil evidence suggested. The Triassic creature weighed ~12 kg as an adult and likely gave birth to pups around 1.7 kg โ a neonatal-to-adult ratio similar to modern placental mammals. Does this mean live birth evolved far earlier and more widely in the animal kingdom than we assumed?
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