Mat farmers

Abstract

How old are the oldest animal trace fossils, and what size did they attain? Several candidate occurrences have been described. Vermiforma antiqua, Plexus ricei and the Trezona Formation structures are very ancient Proterozoic trace fossils. Plexus ricei occupied a now extinct ‘mat–cutter’ niche. The oldest biomat–associated ichnofossils occur in the Mina el Mesquite Formation (Cerro Las Bolas Group) near Sahuaripa, México. Vaqueroichnus stewarti n. ichnogen. n. isp. provides evidence for rudimentary microbial herding, the earliest hint of agrichnial activity in the trace fossil record. The oldest known tracemaker was about 4 mm long.