Ostenocaris

Ostenocaris is a Jurassic species of giant Thylacocephalan crustacean, sufficiently distinct from its relatives to be placed in its own family, Ostenocarididae. It comprises at least two known species, Ostenocaris cypriformis (Arduini, Pinna, Teruzzi, 1980) and Ostenocaris ribeti (Secrétan, 1985). It is an enigmatic taxon, whose physiology and life habits are still poorly known from fossil material. Initially (early 1980s) it was thought to be a filter-feeding, partially infaunal, eyeless organism, or a bizarre barnacle named "Ostenia cypriformis". More recently, as in general for the group to which it belongs, the thylacocephala, the interpretation has shifted to a necrophagous or predatory organism, demersal or nectonic, with highly developed eyes and of deep-sea environment.

It is believed to be a bethonic animal and one of the most important necrophagous animals of its environment. Ostenocaris is the most common fossil of the formation, and the main identified thylacocephalan from the formation. In the first interpretations, the genus was shown as a filter-feeding organism, which used the cephalic sac as a burrowing organ to ensure adhesion to the substrate. Based on the presence of Coprolites associated to the genus, with abundant masses of alimentary residues (hooks of cephalopods, vertebrates, remains of Crustacea) in the stomach of these organisms, Ostenocaris cypriformis was probably a necrophagous organism, and the cephalic sac can be tentatively interpreted as being a burrowing organ employed during the search for food, or as an organ of locomotion with intrinsic motility. Later studies agree that cephalic sac is actually extremely large compound eyes.