Pachygaleus lefevrei was a small hound shark, part of the triakid radiation that included agile predators of coastal and shelf environments. It probably spent much of its time searching for manageable prey in the water column and near the seabed.

Its low asymmetric teeth formed a cutting dentition rather than a set of long piercing fangs. This suggests a varied diet of small fishes, crustaceans and other invertebrates, broadly consistent with the feeding ecology of living hound sharks.

The animal is known mainly from isolated teeth, so its exact body proportions cannot be reconstructed. The fossils nevertheless show that the early Eocene shark fauna contained several small carcharhiniform predators exploiting food resources below the scale of the large lamniform hunters.