Evolution of viviparity

Phylogenetic analyses have revealed that viviparity has originated on more than 115 separate occasions among reptiles (Blackburn 1982, 1985, 1999). An additional 39 origins are identifiable in amphibians and non-tetrapod “fishes” (Blackburn 2005a and more recent work). Thus, viviparity has evolved separately in more than 155 vertebrate clades.  Ongoing analyses continue to update the identifiable origins of viviparity, while proving insight into how these reproductive patterns have evolved (Blackburn 1999, 2006). These analyses and related empirical work have contributed to comprehensive reviews of viviparity and placentation (Blackburn 1992, 1993, 1998, 1999a, 2000, 2005b, 2006; Blackburn & Richardson 2009; Blackburn & Stewart 2011).