Although the presence of an embryo "per se" would be equivocal regarding this issue, the conditions in which the embryo were preserved provide strong evidence that "Dinocephalosaurus" was viviparous. There is no preserved calcified eggshell surrounding the embryo, despite the presence of delicately-preserved calcified elements from other animals at Luoping. This is consistent with the eggshells surrounding the embryos of viviparous reptiles being non-calcified membranes. Furthermore, the relative proportions of the humerus and the fibula in the embryo, compared with the maternal individual and IVPP V13898 from Panxian, indicate that the embryo is around 12% of the size of its mother. Combined with its ossified bones, this suggests that the embryo was at an advanced developmental stage, whereas crocodilians, birds, turtles, and tuataras lay eggs at very early developmental stages.