2012/03/07 by Graciela Piñeiro, Jorge Ferigolo, Melitta Meneghel +1 · 4 citations
Earth and Planetary Sciences · Environmental Science · #Paleontology and Evolutionary Biology #Ichthyology and Marine Biology #Evolution and Paleontology Studies
paper · doi:10.1080/08912963.2012.662230
openalex publication_date 2012/03/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
The earliest undisputed crown-group amniotes date back to the Late Carboniferous, but the fossil record of amniotic eggs and embryos is very sparse, with the oldest described examples being from the Triassic. Here, we report exceptional, well-preserved amniotic mesosaur embryos from the Early Permian of Uruguay and Brazil. These embryos provide the earliest direct evidence of reproductive biology in Paleozoic amniotes. The absence of a recognisable eggshell and the occurrence of a partially articulated, but well-preserved embryo within an adult individual suggest that mesosaurs were viviparous or that they laid eggs in advanced stages of development. Our finds represent the only known documentation of amniotic embryos in the Paleozoic and the earliest known case of viviparity, thus extending the record of these reproductive strategies by 90 and 60 Ma, respectively.