Data from: Facultative oviparity in a viviparous skink (Saiphos equalis)

Facultative changes in parity mode (oviparity to viviparity, and vice
versa) are rare in vertebrates, yet offer fascinating opportunities to
investigate the role of reproductive lability in parity mode evolution.
Here we report apparent facultative oviparity by a viviparous female of
the bimodally reproductive skink Saiphos equalis- the first report of
different parity modes within a vertebrate clutch. Eggs oviposited
facultatively possess shell characteristics of both viviparous and
oviparous S. equalis, demonstrating that egg coverings for viviparous
embryos are produced by the same machinery as those for oviparous
individuals. Since selection may act in either direction when viviparity
has evolved recently, squamate reproductive lability may confer a
selective advantage. We suggest that facultative oviparity is a viable
reproductive strategy for S. equalis and that squamate reproductive
lability is more evolutionarily significant than previously acknowledged.