The Gavialis minor holotype specimen YPM 282 consisted of cranial fragments and isolated vertebrae found from the Manasquan Formation in Monmouth County, New Jersey, dating back to the Ypresian stage of the early Eocene.

Another diagnostic feature thought to distinguish the species from Gavialis was the narrow interfenestral bar of the parietal bone that is relatively smooth and unsculptured when compared to other gavialoids such as Thoracosaurus.

The examination of specimens of Thecachampsoides minor with those of Eosuchus lerichei yielded many similarities between the two species, including the foramen aerum as well as other features such as a long nasal process between the premaxillae, dentary alveoli arranged in pairs, and a W-shaped basioccipital tuberosity.

Some specimens found from these localities are known from nearly complete skulls that provide a more detailed view of the phylogenetic position of Eosuchus, and further aid in distinguishing E. minor from other gavialoids.

A nasal-premaxilla contact and similar dentary and maxillary tooth counts also seem to suggest that there may be a close relationship between the genus and later tomistomines, although these features represent more primitive conditions that changed later in gavialoid history.

Despite this, it is currently accepted that a close relationship between Eosuchus and tomistomines is not the case, and that the similarities between the two may just be superficial and that these characteristics are plesiomorphic to all gavialoids, being lost in more derived members such as the modern Gavialis.

The internal surface of the prefrontal and lacrimal bones of E. lerichei are characterized by concave depressions, which in several marine lizards, iguanas and birds are where salt glands are housed, suggesting this species was capable of saltwater tolerance.