Parotodus
Parotodus, commonly known as the false-toothed mako shark (or false mako shark), is an extinct genus of mackerel shark that lived approximately 53 to one million years ago during the Eocene and Pleistocene epochs. Its teeth, which are found worldwide, are often prized by fossil collectors due to their rarity. The scarcity of fossils is because "Parotodus" likely primarily inhabited open oceans far away from the continents. Description. Initially appearing as a small shark, "Parotodus" gradually increased in size over geologic time and by the Neogene period became one of the largest sharks of its time. A 1999  study estimated the genus to have measured up to in length. The teeth of "Parotodus" are distinctively curved and rarely show feeding damage, which suggests that it mainly preyed on soft-bodied animals. Paleontologists speculate that this included other sharks, including the contemporaneous Megalodon. Classification. Due to the general scarcity and ambiguity of fossils, the familiar placement remains uncertain. Several proposals suggest classifying the genus as a mega-toothed shark, cardabiodont, archaeolamnid, thresher shark, or white shark. Currently, three valid species are generally recognized within "Parotodus". These include "P. benedenii", "P. pavlovi", and "P. mangyshlakensis". However, some scientists, especially those  who identify "Parotodus" as a cardabiodont, do not recognize the latter two as members of the genus. A fourth species was reported by Ward, Nakatani, and Bernard in a 2017 poster from the Oligocene of Japan. The poster stated that the new species is to be named after Yasuhiro Fudouji, the paleontologist who discovered the type specimens, and will be formally described in an upcoming paper. However, the scientific name was not explicitly stated to avoid an accidental invalidation of the taxon. Fossil records. The genus is often regarded as a rare species despite its presence in ocean deposits worldwide . As a result, it is often prized by fossil collectors. Paleontologists believe that "Parotodus" likely inhabited primarily open oceans like the modern oceanic whitetip shark and blue shark. This would explain why fossils of a cosmopolitan animal are so rare, given that open oceans are seldom represented in terrestrial fossil deposits. This hypothesis is additionally supported by how "Parotodus" teeth are unusually common in nodule deposits under the Pacific and Indian Oceans and on islands located far away from continental lands. "Parotodus" fossils have been recovered from fossil deposits in the Azores, Mallorca, Malta, Europe, Madagascar, Kazakhstan, Japan, South Africa , New Zealand, Australia, Peru, California, the East Coast of the United States, and dredged from the Pacific and Indian Oceans.