But, it doesn’t link Great Whites and Megalodon. Longtime readers may remember this three part series on the subject. An interesting new fossil has been discovered that sheds some more light on the subject.
PhysOrg.Com has the story:
The study is based on a remarkably well preserved 4- to 5-million-year-old fossil from Peru of an early white shark species: a complete jaw with 222 teeth intact and 45 vertebrae. Most ancient shark species are known only from isolated teeth. Based on tooth size and analysis of growth rings within the vertebrae, the shark was about 20 years old and 17 to 18 feet long, a size in the range of modern white sharks.
Having the teeth in place allows researchers to see important distinguishing characteristics that help determine a fossil’s genus and species, such as whether a tooth curves toward the outside of the jaw or its midline, Ehret said. He believes the fossil belongs to a white shark species closely related to Isurus hastalis, a broad-toothed mako shark that probably grew to 27 feet long and lived 9 million to 10 million years ago.
Here is the neat part:
Ehret says the shark fossil’s coarse serrations are evidence of a transition between broad-toothed mako sharks and modern white sharks.
“Here we have a shark that’s gaining serrations,” he said. “It’s becoming a white shark, but it’s not quite there yet.”
Don’t you love it when scientists create two new gaps in the fossil record!
The research the story was based on will be published in the March 12th edition of the Journal of Vertebrate Paleontology. The journal’s website also has a story (okay, it’s really a press release like the PhysOrg stuff) on the subject which provides an interesting detail on growth:
The age determination was based on counting the alternating light and dark bands present in the vertebrae, which calcify with age. Such bands have been shown to represent seasonal changes in modern sharks; this was tested in the fossil by examining difference in the isotopic composition of the dark and light bands, which reflects seasonal temperature changes. A modern great white shark of similar age likely would have been larger, suggesting that this fossil species grew at a slower rate.