Date of Award
Master of Science (MS)
Kenshu Shimada Ph.D.
Reported here is the first collective description of a marine vertebrate assemblage from the Codell Sandstone Member (middle Turonian) of the Upper Cretaceous Carlile Shale in Jewell County, Kansas. The Codell Sandstone was deposited during a regression of the Western Interior Seaway, and the fossil locality is described as a relatively shallow, near-shore environment. The collection contains larger, surface collected materials and microfossils washed from sediments represented by isolated teeth, vertebrae, and other skeletal elements as well as coprolites. The fauna consists of 38 taxa, including at least 22 chondrichthyans, 13 osteichthyan fishes, and tetrapod remains belonging to mosasauridae, plesiosauria, and testudines. The fauna is dominated by active, pelagic carnivores, such as Meristodonoides, Anomotodon, Scapanorhynchus, Odontaspis, Cretalamna, Archaeolamna, Cretoxyrhina, Cretodus, Dallasiella, Pseudocorax, Paranomotodon, Belonostomus, Protosphyraena, Xiphactinus, Pachyrhizodus, Enchodus, Apateodus, Aulopiformes indet., Mosasauridae indet., and Plesiosauria indet. The fauna also includes benthic, durophagic fish taxa (e.g., Ptychodus, Rhinobatos, Ptychotrygon, Ischirhiza, Sclerorhynchus, Micropycnodon, and Anomoeodus), a possible planktivore (Cretomanta), and probable scavengers (Squalicorax). Notable occurrences include the oldest example of Ptychodus mortoni from North America, the geologically youngest record of Squalicorax. cf. S. pawpawensis, and the first reported Anomotodon and the second reported Paranomotodon from Kansas.
The examination of the Codell fauna here is significant, because it also allowed the examination of any pattern of change in vertebrate communities as sea-levels and marine habitats changed in the central portion (Colorado, Kansas, and Nebraska) of the Western Interior Seaway. The faunas from different stratigraphic units were grouped based on lithology, designated as near-shore (siliciclastic-based) or off-shore (carbonate-based) ‘community assemblages,’ and reported vertebrate taxa at the genus level were classified based on presumed body size, preferred habitat, and diet. Based on previously published contentions and known ecological patterns of extant marine organisms, I tested the hypotheses that 1) generic richness would be greatest in the near-shore community assemblages, and 2) that near-shore assemblages would generally resemble one another and would differ significantly in ecological composition from the off-shore assemblages. My statistical analyses did not support these hypotheses. Generic diversity was greater in off-shore community assemblages and there were no significant differences in the proportions of vertebrates based on presumed size, habitat, or diet between the near-shore and off-shore assemblages. An inverse relationship between the proportions of lamniform sharks and carnivorous reptilian taxa was found, which may have been due to their similar ecological roles. These findings indicate that, whereas taxonomic compositions of paleocommunities did change or fluctuate as their depositional environment changed, the overall paleoecological dynamics of vertebrate paleocommunities in the central Western Interior Seaway was relatively stable for at least at the generic level regardless of different lithological environments over the 18 million year span investigated here.
Bice, Kelly N., "Fossil Marine Vertebrates from the Codell Sandstone Member of the Upper Cretaceous Carlile Shale in Jewell County, Kansas" (2015). College of Science and Health Theses and Dissertations. 111.