Chondrichthyes: Fossil Record

Fossil ray

Sharks and their kin are sometimes described as "living fossils," and they are indeed part of an ancient clade of vertebrates. Very recently, fossil denticles (scale-like bony pieces embedded in or on the skin) that resemble chondrichthyan scales in minute detail have been found in the Late Ordovician of Colorado (Sansom et al. 1996). More fossil scales that probably belonged to unknown sharks have been found in the Silurian. Aside from these finds, the oldest known complete, identifiable cartilaginous fish date from the middle Devonian. Sharks and their relatives were diverse in the Paleozoic, but most of them were not directly related to living sharks, belonging instead to side groups that died out in the Permian or Triassic. Living sharks, rays, and skates belong to a group known as the Neoselachii. This group may have appeared in the Triassic or even as early as the Permian, but the oldest well-understood neoselachian fossils are Jurassic in age. By the Cretaceous, modern-looking sharks, sawfish, and skates -- such as this beautifully preserved Cyclobatis longicaudatus, from the Upper Cretaceous of Lebanon -- had appeared.

Shark and ray teeth, and sometimes calcified vertebrae, are common fossils in many Cretaceous and Cenozoic deposits. One of the more famous fossil sharks is the Miocene Carcharodon megalodon, with serrated, triangular teeth (pictured on the background of this page) ranging up to 17.5 cm (7 inches) in length. An early reconstruction of Carcharodon from its teeth suggested that this shark reached 30 meters (100 feet) in length. However, this reconstruction was made only from the largest single teeth found, without taking into account the fact that shark teeth taper in size from the center of the mouth to the edges. A revised estimate of the size of Carcharodon puts its length at "only" 12 meters (40 feet) -- about twice the size of the largest great white sharks of today. Click here to view an image of the reconstructed jaws of Carcharodon, courtesy of the Smithsonian Institution.

Various holocephalian fish (those with an upper jaw fused to the braincase) appeared about the same time the earliest sharks did, in the Devonian. They probably included the ancestors of the living chimaeras and ratfish, as well as some other groups that are now extinct (traditionally classified in the Iniopterygii), but their relationships are not well understood.

Got some shark teeth? You may be able to identify them using the Key to Common Genera of Neogene Shark Teeth, by Robert W. Purdy, available from the department of Paleobiology of the National Museum of Natural History.

We have pictures of hybodontid fossils from Ethiopia.

One of the most famous places to find fossil teeth of Carcharodon and other sharks, dating from the Miocene, is Calvert County, Maryland, USA. Find out more about Calvert County sharks -- and other fossils -- from the Maryland Geological Survey.


Carroll, R.L. 1988. Vertebrate Paleontology and Evolution. W.H. Freeman and Company, New York.

Sansom, I.J., Smith, M.M., and Smith, M.P. 1996. Scales of thelodont and shark-like fishes from the Ordovician of Colorado. Nature 379 (15 February 1996): 628-630.