[11] The base of the Carnian Stage is defined as the place in the stratigraphic record where the ammonite species Daxatina canadensis first appears.

In the marine realm, the Carnian saw the first abundant occurrences of calcareous nanoplankton, a morphological group including the coccolithophores.

The bivalve genus Halobia, a bottom-dweller of deep sea environments, differentiated from Daonella at the beginning of this age.

The first dinosaurs (and the pterosaur Carniadactylus) also appeared in this stage, and though at the time they were small and insignificant, they diversified rapidly and would dominate the fauna for the rest of the Mesozoic.

On the other hand, the therapsids, which included the ancestors of mammals, decreased in both size and diversity, and would remain relatively small until the extinction of the dinosaurs.

Fossiliferous localities are many, and are distributed mostly in the surroundings of Cortina d'Ampezzo and in the high Badia Valley, near the village of San Cassiano, after which the formation was named.

This fauna is extremely diverse, including ammonoids, gastropods, bivalves, echinoderms, calcareous sponge, corals, brachiopods, and a variety of less common fossils.

The Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina yielded a very important vertebrate association, including the oldest dinosaurian assemblage.