CAECILIAN VIVIPARITY AND AMNIOTE ORIGINS

A recent evaluation of alternative hypotheses for the origin of the am niotic egg, by mapping a single reproductive-mode character onto a phy logeny of tetrapods, concluded that the alternative hypotheses were eq ually parsimonious. However, this interpretation is dependent upon a m istaken coding of the caecilian amphibians as showing extended embryo retention. Although some caecilians are viviparous, phylogenetic analy ses indicate that oviparity is ancestral for the group. With the codin g of caecilians corrected, the most parsimonious inference is that the ancestral amniotes did not practice extended embryo retention. A revi ew of the available data indicates that the widespread view that a maj ority of caecilians are viviparous is mistaken. Oviparity is the domin ant reproductive mode in caecilians as it is in other living amphibian s.