Chiniquodon (Triassic cynodont) shows evidence of live birth (free pdf)
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Ben Creisler
12:10 PM (7 hours ago) 12:10 PM
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Ben Creisler
A new paper:
Leandro Carlos Gaetano, María de los Ángeles Miceli Baro, Ignacio Alejandro Cerda & Adriana Cecilia Mancuso (2026)
Early origin of viviparity in the mammalian lineage
Frontiers in Mammal Science 5: 1845319
doi: https://doi.org/10.3389/fmamm.2026.1845319
https://www.frontiersin.org/journals/mammal-science/articles/10.3389/fmamm.2026.1845319/full
Viviparity is a reproductive mode in which the embryo completes their development inside the female body. Present-day mammals, with the exception of monotremes, are viviparous, as opposed to the egg-laying reproductive mode of most vertebrates. Non-therian cynodonts are regarded as oviparous although direct evidence on the reproductive modes in extinct taxa is lacking. We identified, in a palaeohistological study, a neonatal line in two bones of the early probainognathian Chiniquodon theotonicus from the Late Triassic of South America. The body mass at birth is comparable to that observed in living placentals, and notably higher than the one registered for monotremes, marsupials, lepidosaurs, crocodiles, and birds. Our results reveal that viviparity is not exclusive of therians among synapsids, pushing back its recognition in the clade ~90–95 Myr.
Free pdf:
Leandro Carlos Gaetano, María de los Ángeles Miceli Baro, Ignacio Alejandro Cerda & Adriana Cecilia Mancuso (2026)
Early origin of viviparity in the mammalian lineage
Frontiers in Mammal Science 5: 1845319
doi: https://doi.org/10.3389/fmamm.2026.1845319
https://www.frontiersin.org/journals/mammal-science/articles/10.3389/fmamm.2026.1845319/full
Viviparity is a reproductive mode in which the embryo completes their development inside the female body. Present-day mammals, with the exception of monotremes, are viviparous, as opposed to the egg-laying reproductive mode of most vertebrates. Non-therian cynodonts are regarded as oviparous although direct evidence on the reproductive modes in extinct taxa is lacking. We identified, in a palaeohistological study, a neonatal line in two bones of the early probainognathian Chiniquodon theotonicus from the Late Triassic of South America. The body mass at birth is comparable to that observed in living placentals, and notably higher than the one registered for monotremes, marsupials, lepidosaurs, crocodiles, and birds. Our results reveal that viviparity is not exclusive of therians among synapsids, pushing back its recognition in the clade ~90–95 Myr.
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New fossil evidence challenges the story of mammalian birth
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