Skeletal and dental anatomy of lamniform shark, Cretalamna appendiculata, from Upper Cretaceous Niobrara Chalk of Kansas

Abstract

ABSTRACT Cretalamna (=Cretolamna) appendiculata is an extinct lamniform shark primarily known by isolated teeth and traditionally classified into Cretoxyrhinidae. Here, a partial skeleton of C. appendiculata from the Upper Cretaceous Niobrara Chalk of Kansas is described. The reconstructed dentition partially corroborated with some articulated teeth on an upper jaw indicates that the shark had a lamnoid tooth pattern. Adjacent teeth apparently abutted each other without overlap and the dentition likely had a cutting function. The reconstruction presented here differs from previously published reconstructed dentitions of C. appendiculata based on isolated teeth or purely disarticulated tooth sets. The overall dental pattern of C. appendiculata is found to be more similar to the pattern of extant Lamna spp. than to that of a cretoxyrhinid, Cretoxyrhina mantelli, possibly indicating that Cretalamna appendiculata may not belong to Cretoxyrhinidae. The estimated jaw lengths indicate an upper jaw overbite, which concomitantly implies a subterminal mouth in the shark. The jaw morphology indicates the presence of large dorsal and ventral quadratomandibularis muscles. The vertebrae of C. appendiculata are confirmed to be of lamnoid type, reaffirming C. appendiculata to be a lamniform. Cretalamna appendiculata probably had a fusiform body with a caudal fin not as elongate as in modern alopiids. The C. appendiculata individual likely measured at least 2.3 m and possibly as large as 3 m in total length. The extant phylogenetic bracket approach indicates that C. appendiculata possessed a dental bulla in each jaw. Cretalamna appendiculata was probably an ecological generalist.