Elasmobranchs have high degree of evolutionary flexibility in reproductive mode. Reversal to egg-laying Identified at base of Rajidae and in S. fasciata . Sequence of squalean taxa in fossil record also supports this reversal. The reversal in S. fasciata is nested in a clade showing multiple oviparity. This may be an artifact of poor knowledge of reproduction in this order.
Results suggest that maternal inputs in live-bearing elasmobranchs have been highly variable.
There has been a trend toward evolution of live-bearing in sharks and rays.