Ophiomorpha: Its morphologic, taxonomic, and environmental significance

Abstract

Ophiomorpha, traditionally one of the most revered environmental indicators among trace fossils, is by no means an unambiguous entity in facies analysis and palaeoecology. Callianassa major, the best known modern analog for the Ophiomorpha-organism, is itself variable ethologically and ecologically, and it is only one of several species of thalassinidean shrimp that routinely construct knobby walled burrows. Other analogs presently known include not only additional species of Callianassa but also certain species of Upogebia and possibly Axius. Each species has its own peculiar range of habits and habitats. The collective result, in both recent and ancient settings, is a broad spectrum of burrow morphologies and environmental distributions. Each occurrence therefore must be evaluated independently, in terms of the specific evidence at hand. Only in this light is Ophiomorpha a valuable aid in environmental interpretation. The gross morphology of Ophiomorpha overlaps with that of such ichnogenera as Ardelia, Gyrolithes, Teichichnus, and Thalassinoides, yet these burrow forms should be retained as separate taxa. Reconized species of Ophiomorpha, also somewhat intergradational, include O. borneensis Keij, O. irregulaire n. sp., and O. nodosa Lundgren. Taxonomic criteria are based upon modes of wall construction rather than upon burrow configuration.