Cretalamna is a genus of extinct otodontid shark that lived from the latest Early Cretaceous to Eocene epoch (about 103 to 46 million years ago). It is considered by many to be the ancestor of the largest sharks to have ever lived, such as Otodus angustidens, Otodus chubutensis, and Otodus megalodon.
Cretalamna was first described by Swiss naturalist Louis Agassiz using five teeth previously identified as the common smooth-hound and collected by English paleontologist Gideon Mantell from the Southerham Grey Pit near Lewes, East Sussex. In his 1835 publication Rapport sur les poissons fossiles découverts en Angleterre, he reidentified them as a new species of porbeagle shark under the taxon Lamna appendiculata.[9] In 1843, Agassiz published Recherches sur les poissons fossiles, which reexamined Mantell's five teeth. Using them, eight additional teeth collected by Mantell, and twenty more teeth collected by various paleontologists in various locations (One tooth found by the 3rd Earl of Enniskillen from the Speeton Clay in Yorkshire; one tooth of the collection of a Strasbourg Museum from an unspecified location; one tooth of the collection of the Hancock Museum from the Marly Chalk near Cambridge; and six teeth of the collection of German paleontologist Heinrich Georg Bronn from chalk around Aachen), he described a species whose teeth had thick bulged roots, lateral cusplets, and extreme variability. Agassiz remarked that some of the examined teeth may be variable enough to belong to a separate species, but ultimately unified them under a new taxon Otodus appendiculatus.[10] The species would later be found in 1958 by Soviet paleontologist Leonid Glickman to belong to a distinct new genus- Cretalamna.[11]
Despite Agassiz's remarks on variability,[10] his ultimately broad interpretation of O. appendiculatus subsequently led the species to become a wastebasket taxon culminating to an interpretation of C. appendiculata as a variable cosmopolitan species with a 50 million year range. This changed when paleontologist Mikael Siversson found that the twenty-five syntypes actually represented a mix of at least six or more different species including three additional genera Dwardius, Cretoxyrhina, and Cretodus. To remedy the taxonomic issue, he redesignated one of the syntypes as the sole lectotype of C. appendiculata in 1999.[1][12] In 2015, he led a study which revisited the taxonomic situation and established a renewed description of the species, which led to the erection of six additional Cretalamna species- C. catoxodon, C. deschutteri, C. ewelli, C. gertericorum, C. hattini, and C. sarcoporthea.[1]