Cosmopolitodus is an extinct genus of mackerel shark that lived between thirty and one million years ago during the late Oligocene to the Early Pleistocene epochs.

[5] It is believed to be an ancestor to the great white shark, an argument supported by the transitional species Carcharodon hubbelli,[6][7] but as of 2021, no phylogenetic analyses have been done for proof.

[8] Throughout the early and mid 20th century, different genera and species of other lamniformes would be clumped into the two taxa as the genus Oxyrhina began to be used as a wastebasket taxon.

[10] Although this conclusion is widely accepted, some scientists disagree, with a study by Whitenack and Gottfried (2010) demonstrating geometrically morphological differences between I. hastalis and I.

The study concluded that there is indeed a putative sister species of C. carcharias distinct from C. hastalis and proposed the taxon Carcharodon plicatilis for it, resolving the paraphyly issue.

[13] However, Yun argued that the tooth fossil remains of Cosmopolitodus and the great white "have been documented from the same deposits, hence the former cannot be a chronospecific ancestor of the latter."

Adult upper teeth are generally 2–4 cm long with an unserrated cutting edge and no lateral cusplets.

True to its name, each tooth is "hooked", the point of which is shifted away from the middle axis, in the direction of the corners of the mouth.

I. desori teeth are much more heterodontic than C. planus and their roots are more uneven in thickness and shape, with more narrow builds and rounder lobes, somewhat making the appearance of a heart.

[12] This form is also commonly labeled by its species synonym xiphodon to reflect its difference from the narrow-form, although this is scientifically invalid.

Trace fossils in the form of tooth marks on the bones of a Pliocene dolphin of the species Astadelphis gastaldii reveal that C. hastalis attacked its prey from below and behind, much like the modern great white shark does.