Research published in the most recent issue of the Journal of Vertebrate Paleontology by scientists from Florida could help elicit the origins of the Great white shark (Carcharodon carcharias).
Dana Ehret, Gordon Hubbell and Bruce MacFadden studied an exceptionally well-preserved fossil of a species of white shark (Carcharodon sp.) from Peru (estimated to be about 5 m long by the authors), consisting of a complete jaw with 222 teeth, and 45 vertebrae, in their paper.
This fossil was collected from approximately 4-million-year-old (early Pliocene) sediments of the Pisco Formation of southern Peru.
Shark paleontologists have long debated the evolutionary origin of the Great white shark.
Some contend that great white sharks evolved from a lineage that included the Megatooth shark (Carcharodon megalodon), the largest shark (and predatory fish) that ever lived.
Others consider the great white shark to be part of the lineage that includes the mako sharks (Isurus) instead (with the Megatooth shark in a separate family, the Otodontidae); the prevailing opinion is for the former view.
The authors demonstrate that the fossil white shark shows morphological characters that are present in both great white shark and Isurus hastalis, a fossil Broadtooth mako shark that lived in the same area 9"10 million years ago.
This means that white sharks are more closely related to mako sharks than to the Megatooth shark, and as a result, the Megatooth shark should be assigned to the genus Carcharocles to reflect its different ancestry.
The authors also analysed the growth rings (annuli) found in the vertebral centra, and concluded that the fossil shark grew at a slower rate than modern great white sharks.
For more information, see the paper: Ehret, DJ, G Hubbell and BJ MacFadden (2009) Exceptional preservation of the white shark Carcharodon (Lamniformes, Lamnidae) from the early Pliocene of Peru. Journal of Vertebrate Paleontology 29, pp. 1"13.