The authors report an oviparous new specimen of the choristodere Ikechosaurus sp. from the Lower Cretaceous of China, confirming the basal archosauromorph affiliation of choristoderes. Phylogenetic analyses of this specimen along with other extinct and extant amniotes suggest that the ancestral amniote displayed extended embryo retention, including viviparity.
- Baoyu Jiang
- Yiming He
- Michael J. Benton
