Caecilian viviparity and amniote origins: a reply to Wilkinson and Nussbaum

An evaluation of the evolution of reproduction in amniotes by the authors has been recently criticized. This criticism is shown to be based on a misrepresentation of our work. The ancestral amniote was certainly oviparous, but this does not necessarily imply that eggs were laid at an early stage of development. The presence of a significant amount of intrauterine development in the earliest amniotes remains as parsimonious as the alternative, despite recent claims to the contrary. The relative rarity of amniote groups that laid heavily mineralized egg membranes in the Palaeozoic may explain why no amniote fossil egg has been found in the Palaeozoic.