New Cynodont fossil discovery pushes back the origin of live birth by 95 million years
Researchers have examined the fossilized remains of Chiniquodon theotonicus, a cat-sized cynodont that lived during the Triassic period in what is now northwestern Argentina, 236 million years ago.
They took thin slices of the animal’s femur and ulna under a microscope and discovered a distinct transition in the bone tissue near the centre of each bone — a ‘neonatal line’, which showed that Chiniquodon produced relatively large offspring, between 10-20% the size of the adult. Using a statistical analysis with over 4,000 other species, it was found that this was consistently grouped with placental Mammals.
This discovery not only pushes back the origin of viviparity by 90-95 million years, but also challenges the long-held assumption that all non-mammalian cynodonts laid eggs, and that live birth arose only once, within the therian mammals that gave rise to modern placentals and marsupials.
Art credit: María de los Ángeles Miceli Baro
Link to original article :https://www.sci.news/paleontology/chiniquodon-theotonicus-live-birth-origin-14990.html