''Isurolamna'' is an extinct genus of

mackerel shark The Lamniformes (, from Greek ''lamna'' "fish of prey") are an order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, such as the gr ...

from the

Paleogene period The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

. It contains at least three species and a fourth is sometimes placed in it. It is thought to be closely related to ''

Macrorhizodus ''Macrorhizodus'' is an extinct genus of Mackerel shark which lived during the early to middle Eocene epoch of the Paleogene period. It is often considered ancestral to ''Isurus'' and sometimes considered part of it. ''Macrorhizodus'' is also lik ...

'', ''

Isurus ''Isurus'' is a genus of mackerel sharks in the family Lamnidae, commonly known as the mako sharks. Description The two living species are the common shortfin mako shark (''I. oxyrinchus'') and the rare longfin mako shark (''I. paucus''). They ...

'', and ''

Cosmopolitodus ''Cosmopolitodus'' is an extinct genus of mackerel shark that lived between thirty to one million years ago during the late Oligocene to the Early Pleistocene epochs. Its type species is ''Cosmopolitodus hastalis'', the broad-tooth mako (other ...

''. ''Isurolamna'' arose in the

Paleocene epoch The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''palaiós ...

during the Selandian age, and was extinct by the close of the Rupelian age of the

Oligocene epoch The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but th ...

. Some features which define this genus include a small, elliptical foramen (hole) in the middle of the lingual side of the root, triangular cusps except on lower interior teeth, and a relatively thick root with nearly vertical margins. The genus has a complicated taxonomic past.

Species

The following species are ascribed to the genus:

References

{{Taxonbar, from=Q104853156 Lamnidae Prehistoric shark genera