Cathepsideja

Cathepsideja is a genus of extinct reptiles that lived during the Late Jurassic period, approximately 150 million years ago. The name was first published in 2023 by paleontologists L. Martinez and J. H. O'Neill after the discovery of several well-preserved skeletons in the Morrison Formation of western North America. Monotypic, the genus contains the single species Cathepsideja robusta, a medium-sized non-avian archosaur estimated to have measured about 3.5 meters from snout to tail.

Taxonomically, Cathepsideja belongs to the clade Phytosauriformes, a group closely related to modern crocodilians. Morphological analysis highlights a distinctive osteology, including a heavily ossified palate and a unique arrangement of the postcranial vertebrae that suggests a semi-aquatic lifestyle. The skull features a deep snout and conical teeth adapted for catching fish, indicating an opportunistic piscivorous diet.

The fossils of Cathepsideja were found in a lacustrine sedimentary layer, supporting the hypothesis that the animal inhabited shallow lakes and floodplain environments. Isotopic analyses of the bone material reveal a range of values consistent with a mixed diet of fish and other small aquatic vertebrates.

Because the genus was described from a limited sample, many aspects of its biology, such as reproductive behavior and ontogenetic development, remain speculative. Further fieldwork in the Morrison Formation and comparative studies with related phytosauriforms may provide additional insight into the ecological role and evolutionary history of Cathepsideja.