''Cosmopolitodus planus'', also known as the hooked-tooth mako shark or hooked mako shark, is an extinct lamnid that lived during the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

epoch from 23 to 5 million years ago. ''C. planus'' can be found only in marine deposits on the

Pacific Rim The Pacific Rim comprises the lands around the rim of the Pacific Ocean. The ''Pacific Basin'' includes the Pacific Rim and the islands in the Pacific Ocean. The Pacific Rim roughly overlaps with the geologic Pacific Ring of Fire. List of co ...

, especially the west coast of the United States.Yabumoto, Y. and Uyeno, T. (1994), Late Mesozoic and Cenozoic fish faunas of Japan. Island Arc, 3: 255–269. doi: 10.1111/j.1440-1738.1994.tb00115.x Teeth belonging to ''C. planus'' can reach lengths of 2.0 in (5.0 cm), and are often found in the

Temblor Formation The Temblor Formation is a geologic formation in California. It preserves fossils dating back from the Late Oligocene to the Middle Miocene of the Neogene period. It is notable for the famous Sharktooth Hill deposit (otherwise known as Ernst Q ...

Bakersfield, California Bakersfield is a city in Kern County, California, United States. It is the county seat and largest city of Kern County. The city covers about near the southern end of the San Joaquin Valley and the Central Valley region. Bakersfield's populat ...

.Malchow, A. 2009. Miocene Shark Tooth Hill Locality, Kern County, California. Geological Society of America North-Central Section - 43rd Annual Meeting (2-3 April 2009)

Description

''Cosmopolitodus planus'' exists only around the Pacific Rim areas, including

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, the eastern coast of

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, and

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, while being most common in Southern California, especially at

Sharktooth Hill The Temblor Formation is a geologic formation in California. It preserves fossils dating back from the Late Oligocene to the Middle Miocene of the Neogene period. It is notable for the famous Sharktooth Hill deposit (otherwise known as Ernst Quar ...

near

Bakersfield Bakersfield is a city in Kern County, California, United States. It is the county seat and largest city of Kern County. The city covers about near the southern end of the San Joaquin Valley and the Central Valley region. Bakersfield's populat ...

. With teeth up to two inches long, ''C. planus'' would probably be around the size of a modern

great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is nota ...

and most likely preyed upon the fish, pinnipeds, and smaller cetaceans of its time.

Teeth

''Cosmopolitodus planus'' teeth are somewhat similar to those of other mako sharks, especially the extinct species ''

Cosmopolitodus hastalis ''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 ...

'' and ''

Isurus desori ''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 ...

''. Adult upper teeth are generally 2–4 cm long with an un

serrated Serration is a saw-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied pr ...

cutting edge and no lateral

cusp A cusp is the most pointed end of a curve. It often refers to cusp (anatomy), a pointed structure on a tooth. Cusp or CUSP may also refer to: Mathematics * Cusp (singularity), a singular point of a curve * Cusp catastrophe, a branch of bifurca ...

lets. True to its name, each tooth is "hooked", the point of which is shifted away from the middle axis, in the direction of the corners of the mouth. In this, the teeth of ''C. planus'' and ''I. desori'' differ from ''C. hastalis''. ''I. desori'' teeth are much more heterodontic than ''C. planus'' and their roots are more uneven in thickness and shape, with more narrow builds and rounder lobes, somewhat making the appearance of a heart. But the crowns of the lower teeth of this species are described to be more straight and identical to the lower teeth of ''C. hastalis''.Ciampaglio, C., Ricketts,D. Miocene Madness: Fossil Finder ID and Information Guide. Bakersfield, California. Buena Vista Museum of Natural History. The hooked teeth, which probably would be efficient for gripping prey, would suggest a diet of smaller and medium-sized animals.

Classification

The hooked-toothed mako was initially believed to be a true mako shark under the genus ''

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 ...

'', hence its colloquial name "mako." However, the species is now believed to be descended from the narrow-form of the broad-tooth "mako" ''

'', and its scientific name was thus reassigned to ''Cosmopolitodus planus'' in 2021. Although some paleontologists previously argued that ''

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 ...

'' should be a synonym of ''

Carcharodon ''Carcharodon'' () is a genus of sharks within the family Lamnidae. The only extant member is the great white shark (''Carcharodon carcharias''). Hubell's white shark (''Carcharodon hubbelli'') is an extinct member of this genus. Megalodon ...

'' due to ''

'' being an ancestral species, Yun argued that the tooth fossil remains of ''

'' and

"have been documented from the same deposits, hence the former cannot be a chronospecific ancestor of the latter."

References

{{Taxonbar, from=Q25094566 Lamnidae Miocene sharks