Pathologic tooth deformities in modern and fossil chondrichthians: a consequence of feeding-related injury

Deformed teeth are found as rare components of the dentitions of both moder n and fossil chondrichthians. Tooth deformities occur as bent or twisted to oth crowns, missing or misshaped cusps, atypical protuberances, perforation s, and abnormal root structures. Deformed tooth files consisting of unusual ly overlapped or small teeth, or teeth misaligned in the jaw also occur in modern forms, but deformed tooth files generally are not recognizable in fo ssils due to post-mortem dissociation of teeth and jaws. A survey of 200 mo dern lamniform and carcharhiniform sharks as well as literature sources ind icate that such deformities are produced by feeding-related injury to the t ooth-forming tissue of the jaws, particularly by impaction of chondrichthia n and teleost fin and tail spines. Tooth counts for several late Cretaceous genera, based on material recovered from coastal plain sites from New Jers ey to Alabama, suggest that the frequency of occurrence of deformed teeth i n a species varies from about 0.015% in Squalicorax kaupi to about 0.36% in Paranomotodon sp. Tooth counts for modern lamniform and carcharhiniform sh arks yield a comparable range in frequency of tooth deformities. Variation in frequency of tooth deformity may reflect interspecific differences in fe eding behavior and dietary preferences. There is no suggestion in our data of any strong patterns of temporal variation in tooth deformity frequency, or of patterns reflecting chondrichthian phylogenetic history and evolution . Skeletal components of the probable prey of the Cretaceous species are pr eserved in the same horizons as the deformed teeth, and also are found with in co-occurring chondrichthian coprolites. square Chondrichthians, Cretaceo us, feeding injury, pathology, tooth deformities.