The symmetrical, flexible teleost fish 'tail' has been a prime example of recapitulation - evolutionary change (phylogeny) mirrored in development (ontogeny). Paleozoic ray-finned fishes (Actinopterygii), relatives of teleosts, exhibited ancestral scale-covered tails curved over their caudal fins. For over 150 years, this arrangement was thought to be retained in teleost larva and overgrown, mi...

The phylogenetic positions of frogs, salamanders, and caecilians have been difficult to establish. Data matrices based primarily on Paleozoic taxa support a monophyletic origin of all Lissamphibia but have resulted in widely divergent hypotheses of the nature of their common ancestor. Analysis that concentrates on the character states of the stem taxa of the extant orders, in contrast, suggests...

Mesozoic-Cenozoic scleractinian corals were not derived by descent from late Paleozoic rugose corals. Rather, they probably originated from a group of Paleozoic sea anemones that survived into the Mesozoic after the extinction of the Rugosa at the end of the Paleozoic. This conclusion is based on three arguments: 1. all scleractinians have cyclic septal insertion in contrast to the serial inser...

Two distinct traditions exist in the study of ancient ichnofaunas, which may be termed the ethological (invertebrate ichnology) and the biotaxonomic (tetrapod ichnology). Consequently, there are two different kinds of ichnofacies, each peculiar to one tradition, and we term them ethoichnofacies (invertebrate ichnofacies) and biotaxonichnofacies (tetrapod ichnofacies). In the Paleozoic, the Chel...