User:Spotty11222/Cretalamna

Cretalamna is an extinct genus of shark.

Teeth
The teeth of C. appendiculata (no attempt will be made to differentiate the sub-species) are best characterized by their smooth triangular cusp, broad triangular lateral cusplets and a bilobate root, which has a lingual protuberance and foramen but lacks a nutrient groove. The crown of anterior teeth is elongated and erect and in laterals, the cusp is shorter and distally directed (more acutely in upper teeth). The basal margin of the root is "U" in shape.

Dentition-design
Shimada (2007) described a partially articulated3 C. appendiculata skeleton from the Smoky Hills Chalk (Upper Cretaceous, Logan, Co., KS) housed in the LA County Museum (LACM 128126). He concluded that the species, based on morphological features, was a medium-sized (to 3m) pelagic lamniform with a cutting dentition designed for generalized feeding. He noted that the dentition-design did not compare well with that of Cretoxyrhina mantelli but was much more lamnid-like; he elected to leave this genus ascribed to Cretoxyrhinidae, but questioned the validity of that assignment.

The largely disarticulated teeth from this specimen were arranged by Shimada following a series of described steps (p 588) which might be briefly summarized as tooth size and cusp inclination; upper vs lower determinations were based on cusp width and thickness. Once complete, he found the arrangement could be validated (in part) by the anterior/medio-lateral crown tips articulated in the right palatoquadrate (p 591). Remaining upper tooth-positions mapped to "depressions for tooth rows in the inner surface of the palatoquadrate" (Shimada pers com 2007). In this paper, the material appears to be excellent, the methodology well defined (except for the underlying rule for tooth-orientation when capturing metrics) and the validation reasonable -- characteristics often lacking with reconstructed dentition-sets.