[9][10] There has been much debate and speculation about the evolutionary origin and relationships between Isurus and its closest relatives, including the extant great white shark (Carcharodon carcharias).

Molecular clock analyses place the last common ancestor of Isurus and Carcharodon between 43–60 million years ago during the Late Paleocene-Early Eocene.

[11] This insight should guide efforts to better resolve the fossil ancestry of both lineages, by providing a window of time in which to search for ancestor candidates.

Many fossil species of Lamnids have historically been placed under Isurus, which are now largely considered separate genera.

[citation needed] They both have a distinctive blue-gray color scheme common among mackerel sharks.