Morphology, ontogeny, and life habit of Agnostus pisiformis from the Upper Cambrian of Sweden.

Abstract

The morphology and early ontogeny of Agnostus pisiformis (Linnaeus 1757) is described on the basis of >100 phosphatized, mostly enrolled specimens, etched from nodular limestones of the Upper Cambrian Agnostus pisiformis Zone, Vastergotland, Sweden. Those features which point to affinities with the polymerid trilobites are most clearly in the exoskeleton and in the ontogeny. The numerous modifications of the morphology of A. pisiformis from the general polymerid trilobite body plan and features hitherto unknown from trilobites and even other arthropods confirm the separate rank of the Agnostina within the Trilobita.-from Authors