Anurans

Abstract

When they first appear in the fossil record during the Jurassic, frogs appear essentially modern in their skeletal anatomy (Romer and Parsons 1977; Carroll 1988). Frogs, caecilians and salamanders share a number of derived features that have led herpetologists to ally them in a single group, the subclass Lissamphibia (see Parsons and Williams 1963; Duellman and Trueb 1986). All these are mainly small animals that depend on cutaneous respiration, have spool-shaped vertebrae, and most members of all three orders have a peculiar, so-called pedicellate, tooth structure in which the base and crown are separated by a zone of fibrous tissue (Carroll 1988). Despite these similarities, frogs, salamanders and caecilians are very different from one another in skeletal structure and ways of life, both now and throughout their known fossil history (Freytag 1974; Heusser 1974a; Young 1981; Duellman and Trueb 1986).