Selachians from the Greenhorn Cyclothem (“Middle” Cretaceous: Cenomanian–Turonian), Black Mesa, Arizona, and the Paleogeographic distribution of Late Cretaceous selachians

Abstract

Black Mesa in northeastern Arizona exposes sediments of late Cenomanian–Turonian age deposited during the transgressive–regressive Greenhorn cyclothem. These sediments contain a diverse selachian fauna that consists of 21 taxa: Hybodus sp., Ptychodus whipplei, P. decurrens, P. cf. P. mammillaris, Chiloscyllium greeni, Chiloscyllium sp., Scapanorhynchus raphiodon, Cretodus semiplicatus, Cretolamna appendiculata, C. woodwardi, Cretoxyrhina mantelli , cf. Leptostyrax sp., Squalicorax falcatus, Rhinobatos sp., Pseudohypolophus mcnultyi, Protoplatyrhina hopii n. sp., Ischyrhiza schneideri, I. avonicola, Onchopristis dunklei, Ptychotrygon triangularis, P. rubyae n. sp., and five types of dermal denticles. Two selachian assemblages, a nearshore and a deeper water assemblage, are present in this fauna. Though there is some provincialism in North Africa, Europe, and North America during the Greenhorn marine cycle, the wide dispersion of some shark taxa and the great similarities between widely separated selachian faunas are striking.