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ABSTRACT-Several specimens of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli (Agassiz), from the Niobrara Chalk of Kansas suggest that the shark fed on teleosts, mosasaurs, and possibly plesiosaurs. These animals are active vertebrates, so C. mantelli probably occupied the apex of the food chain in the Late Cretaceous seas. This top predator, however, was probably scavenged frequently by anacoracid sharks. Carcharodon carcharias (great white shark) and carcharhinid sharks are considered as the modern guild counterparts for Cretoxyrhina mantelli and anacoracids, respectively.
INTRODUCTION
MOST CHONDRICHTHYAN fossils are represented by isolated teeth due to low fossilization potential of cartilaginous skeletal elements and high fossilization potential of hard dental components. The size and morphology of teeth have thus often been the only key to decipher their feeding behavior (e.g., Siverson, 1992; Welton and Farish, 1993). Some exceptions include cases of association of shark teeth with a vertebrate skeleton (e.g., Cione and Medina, 1987; Repenning and Packard, 1990) and tooth marks of one or more sharks preserved on the surfaces of vertebrate bones (e.g., Demere and Cerutti, 1982; Cigala-Fulgosi, 1990) as evidence of shark feeding.
While most Late Cretaceous sharks in Kansas occur as isolated teeth, several specimens of Cretoxyrhina mantelli (Agassiz, 1843) (Lamniformes, Cretoxyrhinidae: for taxonomic review, see Cappetta, 1987), from the Smoky Hill Chalk Member of the Niobrara Chalk (for stratigraphy, see Hattin, 1982) preserve associated skeletal and dental elements along with remains of one or more other marine vertebrate taxa in the same bedding horizon. This paper documents such specimens of C. mantelli, and considers its trophic level during the deposition of the Smoky Hill Chalk. All examined specimens are deposited at the University of Kansas Museum of Natural History (KUVP) in Lawrence, Fort Hays State University, Sternberg Museum of Natural History (FHSM) in Hays, Kansas, University of Nebraska State Museum (UNSM) in Lincoln, or the Royal Ontario Museum (ROM) in Toronto, Canada.
TAPHONOMIC CONSIDERATIONS
Animal remains with embedded shark teeth represent direct evidence of paleoecological relationships between the shark and animals. Other vertebrate remains occurred adjacent to the Cretoxyrhina elements described herein, however, are also considered to represent evidence of paleoecological relationships between them, and not simply accidental associations through depositional processes. This interpretation is supported by the following taphonomic evidence: 1) the specimens...