A surfeit of theropods in the Moroccan Late Cretaceous? Comparing diversity estimates from field data and fossil shops

An unusually high proportion of large-bodied carnivorous theropod dinosaurs has been reported from the Moroccan Late Cretaceous Kem Kem Formation, a well-known package of North Africa vertebrate fossil-bearing sediments. We investigate whether recorded proportions of predator and prey taxa in Kem Kem sediments are real, or an artifact generated by collecting biases, by comparing field data to counts of fossil vertebrates from Moroccan fossil shops. The application of common techniques for standardizing ecological survey data confirms that previous workers have been misled by the acquisition by museums of specimens from commercial collectors rather than from detailed field surveying. Claims that an unusual number of theropod dinosaurs were present in North Africa Late Cretaceous ecosystems are likely the result of biases due to both commercial activity and collectorship biases.