''Macrorhizodus'' is an extinct genus of Mackerel shark which lived during the early to middle Eocene epoch of the

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

period. It is often considered ancestral to '' Isurus'' and sometimes considered part of it. ''Macrorhizodus'' is also likely ancestral to '' Cosmopolitodus''. It seems to be related to '' Isurolamna''. 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, 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