Ostenocaris is a Jurassic species of giant Thylacocephalan crustacean, sufficiently distinct from its relatives to be placed in its own family, Ostenocarididae.

[2] Later studies agree that cephalic sac is actually extremely large compound eyes.

[3] Ostenocaris lived during the Sinemurian age of the Lower Jurassic, and has been found in rocks at two sites in the Italian Lombardische Kieselkalk Formation.

This formation is known for its good preservation, with fossils of annelids, fishes, and plants, representing a relatively depth shelf deposit, where Thylacocephalans are the most abundant organisms.

This species lived in a bathyal zone environment, in a depth most probably exceeding 200 m.[5]