Knowledge of extinct cartilaginous fishes depends primarily on their tooth remains. Familiarity with galeoid (shark) teeth is widespread, but it is restricted for batoid (ray) teeth, as illustrated by the Cretaceous batoid, Ptychotrygon.

Until now this taxon has appeared to be a monotypic genus restricted to the Upper Cretaceous of northwestern Czechoslovakia and adjacent Germany. The writers have found it to be widespread in the Upper Cretaceous of Texas and diversified into three species, including the original of Czechoslovakia.

These findings permit emendation of the genus, which is distinguished most readily from others, such as Squatirhina, by its uniserial interlocking arrangement of teeth; this arrangement is indicated by the presence of an anterior proboscis and a posterior receiving concavity on each crown.

From the writers' data it appears that ptychotrygonids may prove to be widespread in the Gulf coastal plain and of some chronostratigraphic value. Because of their size, typically 2 mm maximum dimension, they normally will be found in micropaleontological samples.

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