Carpoid

Ponticulocarpus robinsoni

• Cambrian
• Spence Shale
• Wellsville Mountains, Box Elder County, Utah, USA

Size: 2 cm

Found exclusively in the Cambrian of Utah, Ponticulocarpus robinsoni (Sumrall & Sprinkle 1999) is a cornute, a type of carpoid possessing a bizarre asymmetrical theca and a single tail-like appendage known as an aulacophore. P. robinsoni exhibits some unusual features compared to other cornutes: incredibly wide and thin glossal and spinal processes (thought to assist in burrowing into substrate), a uniquely closed posterior margin due to a neomorphic extra plate, and the several connections or "bridges" between parts of its marginal rim (thought to function in strengthening the thecal margin). This last feature also gives the taxon its name, with ponticulus being Latin for "little bridge".

This specimen exhibits both the glossal and spinal processes, the bridges and small irregular plates throughout the superior face of the theca, and an aulacophore with partially opened cover plates (visible as the line of spine-like "fins" along its edge).