Development of the oral disc in embryos and larvae of the agile frog, Ranadalmatina

The mouth of the agile frog Rana dalmatina (Amphibia, Anura) started to for m during stage 21, at the age of 18 days. The larval period began at stage 25, when the horny tablets appeared. During the larval period, the number o f horny labial teeth, as well as labial papillae, increased. In stage 29, t he dental formula completed as I:2-2/1-1:III and persisted until stage 40, when metamorphosis of the oral disc commenced. An alternative dental formul a I:2-2/2-2:II was found in 21 % of the observed individuals. Subsequently, the larval mouth structures resorbed and small adult-like jaws developed.