Origin of the Modern Terrestrial Vertebrate Food Chain

ABSTRACT The Bromacker vertebrate fossil assemblage is strikingly unique compared to those of the highly fossiliferous, widespread Early Permian deposits of the USA in exhibiting: 1) total absence of aquatic and semi-terrestrial forms, 2) greatly reduced abundance and diversity of basal synapsids (“pelycosaurs”) that fulfilled the role of apex predators, and 3) high abundance and diversity of terrestrial herbivorous taxa. That is, the composition of the Bromacker vertebrate assemblage and the relative abundances of its taxa are difficult to reconcile with current knowledge of the well-documented examples of the Early Permian mixed aquatic-to-terrestrial trophic systems in the USA. The explanation given here for these unique paleobiological features is that the vertebrate assemblage reflects an adaptation to a rarely encountered paleoenvironment, the small, far inland, isolated, internally drained Tambach Basin. It is hypothesized that the Early Permian Bromacker assemblage is unique in representing an initial stage in the evolution of the modern terrestrial trophic system or food chain.