#chondrichthyan

A fossilized shark tooth of an Otodus megalodon from New Caledonia. Teeth from this locale are often very worn due to being dredged from the bottom of the Pacific Ocean off the coast of New Caledonia. However, this tooth does still retain remnants of serrations.

A fossilized shark tooth of a great white shark, or Carcharodon carcharias from the Pisco Formation in Sacaco, Peru. This Pliocene aged great white shark tooth shows nice shades of blue colors known from this deposit.

A Carboniferous chondrichthyan tooth whorl of an Edestus heinrichi or scissor tooth shark from the Carbondale Formation in Jackson County, Illinois, United States. Often found in coal mines, these bizarre shark-like cartilaginous fish are also known as coal sharks. Similar to its more famous relative, Helicoprion, Edestus and other shark-like eugeneodonts did not lose their old teeth like true sharks. Instead, this strange animal continued to grow out its tooth whorls, increasing the number of crowns.

A fossilized shark tooth of a broadnose sevengill shark, or Notorynchus cepedianus from the Aurora, Beaufort County, North Carolina, United States. The teeth of these cow sharks can be found in both the Miocene aged Pungo River Formation and the Pliocene aged Yorktown Formation in this area. This species is still alive today and is the only surviving member of its genus. While the number of cusps could lean towards Hexanchus, the coarse serrations on the mesial edge suggest Notorynchus.

A Permian chondrichthyan tooth of a Glikmanius occidentalis from the Council Grove Group in Wabaunsee County, Kansas, United States. A member of the shark-like ctenacanths, this species was previously referred to the genus Cladodus.

A pair of fossilized shark tooth of a Carcharodon hastalis from the Round Mountain Silt Member, Temblor Formation in Sharktooth Hill, Kern County, California, United States. This species of Carcharodon is currently suspected to be the direct ancestor of the great white shark, or Carcharodon carcharias with Carcharodon hubbelli bridging the gap as a transitional species. This species is also known as Cosmopolitodus hastalis or the giant mako (though it is not a true mako being closer to white sharks) with two distinct morphologies being present, the broad-tooth and narrow-tooth type, the former sometimes placed in its own species as Carcharodon plicatilis. Carcharodon hastalis (the broad-tooth morphology) is interestingly a larger species than their modern day great white sharks descendants.

A fossilized shark tooth of a Ptychodus marginalis from the Fairport Chalk Member, Carlile Shale in Ness County, Kansas, United States. This species is similar to that of Ptychodus polygyrus, and some specimens of this species have been reassigned to P. marginalis.

A worn fossilized shark tooth of a great white shark, or Carcharodon carcharias from the Naarai Formation in Cape Nagasakibana, Choshi City, Chiba, Japan. Fossils from this deposit are between the Upper Miocene to Lower Pliocene in age. The Japanese name for this world famous shark is "hohojirozame" which literally translates to "white-cheeked shark" (not the confused with the whitecheek shark, Carcharhinus dussumieri).