User:Macrophyseter/sandbox5

Macrorhizodus is an extinct genus of mackerel shark in the family Lamnidae that lived during the early to late Eocene epoch (~56-34 mya), with a possible extension into the early Oligocene. It was widely distributed throughout the ancient Atlantic and Tethys Oceans, with fossils known from Kazakhstan, Africa, Europe, the Americas, and Antarctica. Up to six species may be attributed to the genus, although some are synonymized with M. praecursor or moved to other genera by some paleontologists, which have been hypothesized to form an anagenetic lineage. Macrorhizodus is hypothesized to be the ancestor of the Carcharodon white sharks.

Taxonomic history
The type species was first described by Ukrainian naturalist Afanassi Semjonowitsch Rogowitsch in 1860 from a tooth collected from a late Eocene clay deposit in Kyiv, which he named Oxyrhina falcata. In 1905, French paleontologist Maurice Leriche described the subspecies Oxyrhina desori praecursor, the species being an Oligocene mako shark, from Eocene teeth recovered from deposits in Brussells, Belgium and surrounding area. He distinguished the taxon as the teeth were broader and stocker than the main species, as well as being of an earlier age. In 1910, Leriche described another subspecies named O. desori flandrica from a partial skeleton of 42 teeth and 69 vertebrae from the Boom Formation of Bazel, Flanders. In 1942, he elevated O. desori praecursor to a distinct species and assigned another subspecies under it based on teeth from Alabama, which he named O. praecursor americana. The three taxa would later be coalesced by Glickman (1964) into a new genus: Macrorhizodus. Glickman also described the species M. gigas from teeth in Kazakhstan. The final species, M. nolfi, was described by Zhelezko & Kozlov (1990) from the same country.