Depositional environments of a Middle Jurassic terrestrial vertebrate assemblage, Huizachal Canyon, Mexico

Abstract

ABSTRACT A large assemblage of vertebrate fossils from the La Boca Formation in Huizachal Canyon, near Ciudad Victoria, Tamaulipas, Mexico, is preserved in a unique setting: debris-flow sediments deposited over a landscape with at least modest topographic relief. Angular feldspar lathes in the rock suggest that deposition was associated with penecontemporaneous volcanism. The ~8,000-specimen collection from Huizachal Canyon includes the tritylodontid Bocatherium mexicanum, the burrowing diapsid Tamaulipasaurus morenoi, three types of mammals, two crocodyliforms, two types of dinosaurs, a pterosaur, and three sphenodontians. The fossils generally occur as small (~5 mm), isolated bones or bone fragments, but 35 articulated or associated specimens have been found. No turtles or fishes have been identified, implying a terrestrial source for this assemblage. Biostratigraphic and preliminary radiometric evidence suggest an early Middle Jurassic age, making this assemblage the only substantial terrestrial Middle...