7. Viviparous caecilians and the salamander have
a fetal dentition involved in ingesting the nutrient
secretion. However, the salamander uses “larval”
teeth of the sort present in larvae of many species;
the several viviparous species of caecilians have a
fetal dentition that is unique in tooth crown shape
and distribution among species and relative to the
adult condition. The developing frog may make use
of the fimbriae around its mouth as a “sponge” to
gather the nutrient secretion for ingestion.
yolk sac and even the chorionic and allantoic extraembryonic
membranes function as placentae.