Maternal provisioning of embryos Most common form of maternal input for live-bearers is matrotrophy. Several distinct modes evolved independently. Oophagy evolved twice. Discussion Ancestral reproductive mode Results supported by earlier suggestions that egg-laying is ancestral in sharks, rays and ratfishes. Absence of claspers in cladoselachians may support this.
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.