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).

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.

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.

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.

[15] In 1897, French paleontologist Fernand Priem described a single tooth from the Köpinge Sandstone in Scania, Sweden under the taxon Lamna borealis.

[18] In 1972, French ichthyologist Henri Cappetta described teeth from Maastrichtian deposits near the Mentès well in Tahoua, Niger, which he assigned to the subspecies Lamna biauriculata nigeriana.

[1] In 2018, American paleontologists Jun Ebersole and Dana Ehret described a new species of Cretalamna from various teeth from the Eutaw Formation and Mooreville Chalk in Alabama, which they named C.

[10] The species name borealis is derived from the Latin boreālis (northern); this is a reference to its discovery from fossil deposits in Sweden, a boreal locality.

[1] The specific epithet of C. maroccana is a feminine form of the Latin word maroccānus (Moroccan), a reference to its type locality in Morocco.

The specific epithet of C. gertericorum is structured differently; it is derived from the names "Gert", "Eric", and the Latin suffix -orum (a masculine plural declension).

Originally, Glickman described the genus with the intention of naming it as 'Cretolamna' , but during publication of the corresponding 1958 paper a typographical error occurred, with the print misspelling it as 'Cretalamna' .

Based on vertebral comparisons with various extant lamniforms and Cretoxyrhina, a 2007 study by Kenshu Shimada estimated a total length of 2.3–3.0 metres (8–10 ft) for the most complete skeleton of a large individual (LACM 128126; C. hattini holotype[1]).

[26] In 2020, Shimada and colleagues estimated the maximum possible length of C. borealis up to 3.5 meters (11 ft) based on an upper jaw tooth specimen (LO 11350t) from Åsen locality.

[27][1] The body plan of Cretalamna is almost completely known, informed by near-complete fossil impressions with soft tissue preserving the shark's outline from the Hjoula lagerstätte in Lebanon as documented by Pfiel (2021) and Greenfield (2022).

[29] Such a body plan is indicative of an active fast-swimming pelagic shark likely partially warm-blooded through regional endothermy.

Fossil evidence of Cretalamna is found in deposits representing a diverse set of marine environments, indicating that it was able to adapt to a wide range of habitats.

[24] It is widely believed that Otodus (and thus Carcharocles) is derived from Cretalamna due to its strong similarity to certain species within the genus.