''Macrorhizodus'' 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 ...

which lived during the early to middle

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

epoch of the Paleogene period. It is often considered ancestral to ''

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 sometimes considered part of it. ''Macrorhizodus'' is also likely ancestral to ''

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 ...

''. It seems to be related to ''

Isurolamna ''Isurolamna'' is an extinct genus of mackerel shark from the Paleogene period. It contains at least three species and a fourth is sometimes placed in it. It is thought to be closely related to '' Macrorhizodus'', ''Isurus'', and '' Cosmopolito ...

''. It is known from isolated teeth and vertebral centra as well as at least two associated dentitions. It is an incredibly widespread shark, known from every continent except Australia. This includes a report from Antarctica.

Species

The genus is composed of the following species: This genus appears to have undergone

anagenesis Anagenesis is the gradual evolution of a species that continues to exist as an interbreeding population. This contrasts with cladogenesis, which occurs when there is branching or splitting, leading to two or more lineages and resulting in separate ...

, making it difficult to draw lines between species. Some authors prefer to lump and others to split. The early Oligocene species ''Macrorhizodus flandricus'' ascribed to this genus now usually considered to be a synonym of ''Isurus desori'', sometimes styled ''Isurus desori flandrica''. However, ''I. desori'' might itself be a junior synonym to '' I. oxyrhincus''. This confusion stems from the proximity of ''Macrorhizodus'' to ''Isurus''.

References

{{Taxonbar, from=Q104853580 Lamnidae Prehistoric shark genera Eocene sharks