REVISING AWAY A LIVING FOSSIL: RESTUDY OF FOSSIL NOTOSTRACANS FROM THE PERMO-TRIASSIC OF THE USA

Notostracans are generally thought of as ‘living fossils.’ However, the taxonomy of the known fossils is sorely neglected. A recent revision by Geyer et al. (2024) illustrated the depth of this problem by examining Triassic-aged specimens from France.

Notostracan fossils are known from two sites in the United States: the Permian-aged Enid Formation in Oklahoma and the Triassic-aged Bull Run Formation in Virginia. Both have been assigned to the extant genus, Triops. This assignment was done with little critical analysis of the actual fossils. Re-examination of the specimens from Oklahoma have revealed a carapace fundamentally incompatible with the dorso-ventrally compressed carapace of Triops. Instead, it belongs to the genus Olesenocaris, previously only known from the Triassic of France. The Virginian specimens have a very weak mandibular bulge and angular insertions for the caudal furca. It seems to represent a new species of the genus Apudites.

The myth of Triops cancriformis as a living fossil is only plausible with a superficial treatment of the fossil anatomy and systematics. Detailed restudy makes it clear that, even though the morphology is evolutionarily conservative, Triops cancriformis does not have a fossil record.