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Try not to think about how big this 300-million-year-old “supershark” was compared with an average human. J. Maisey/American Museum of Natural History
When you hear the term “supershark,” you probably think of a massive prehistoric creature that could eat modern sharks for breakfast, like the long-extinct megalodon that’s spawned a number of movies and books, or possibly some kind of anthropomorphic shark superhero that saves people trapped in burning buildings and then eats them.
Mark McKinzie and Robert Williams, two amateur fossil hunters from the Dallas Paleontological Society, came across some remains of that first type of supershark in rocks in Jacksboro, Texas. The find is believed to be fragments of the brain cases of a type of shark that, while smaller than the mighty megalodon, was still 25 percent bigger than a modern great white shark, according to the society. The surprising part is that they’re considerably older than previously found giant shark specimens, by about 170 million years.
The Dallas Paleontology Society donated the fossils to the American Museum of Natural History in New York for further study. Museum researchers presented their findings on these specimens on October 16 at the annual meeting of the Society of Vertebrate Paleontology in Dallas.
John Maisey, the curator of vertebrate paleontology at the American Museum of Natural History who studies rare shark and shark-like fish fossils, says the fossil brain cases collected by McKinzie and Williams suggest these unidentified “supersharks” may have had skulls approximately 2.5 feet (76 centimeters) long, and based on that, the larger of the two sharks may have measured as long as 26 feet (8 meters).

Modern great white sharks, Maisey told CNET, “top out at about 6 meters (19.6 feet) and you hear stories about bigger ones, but the biggest known great white shark that’s been measured is around 22 feet.”
He describes this type of prehistoric shark as a “massive top predator” that swam in fairly warm oceanic conditions and might have been able to maintain its blood temperature just like modern sharks such as the great white and the mako.
Maisey said they aren’t sure if these fossils came from a known or unknown prehistoric shark species because they “can’t identify the species or genus without any associated things like teeth.” However, he said he believes these are either from a new undiscovered species or a toothy, extinct species called Glikmanius occidentalis.
“What we’ve got are bits of cranium or a brain case that don’t have any real diagnostic features, but we can see what group they belong to,” Maisey said. “There are other, more complete fossils of these kinds of sharks that do have similar teeth.”
The age and size of these fossils make it a unique find, Maisey explained.
“This shark from Texas is somewhere around about 300 million years old, and that’s pretty far back from other Cretaceous ones that tend to be about 75-80 million years old, so there’s a gap in between from the age of the dinosaurs,” Maisey said. “You also never see sharks that are more than 3 meters [9.8 feet] long. The biggest one I ever saw was more than 3 meters and it didn’t have very big teeth. That doesn’t mean that they didn’t exist, but we just haven’t seen them.”

Maisey notes that without a complete skeleton or other remains from the surrounding area, the size of the sharks that left these fossils can only be roughly estimated.
“All of these [estimates] are very preliminary since we only have these fragments,” he said. “We know what they are and we know they were big and we can only estimate their body size.”
He applauded the efforts of McKinzie and Williams, and other amateur fossil hunters who collect and donate such specimens for scientific research. For example, in August, National Geographic reported that Jason Osborne of nonprofit fossil collection group Paleo Quest helped collect a 5-million-year-old baleen whale skull in a Virginia swamp that Osborne had discovered two years earlier.

Maisey says these enthusiasts are doing a great service by not only dedicating their spare time to finding these specimens but also donating them for scientific study instead of just sticking them on a mantle or packing them away in a private collection.
For something like that whale skull, “If we didn’t have these people going out and trying to find it, we never would have had it,” Maisey said.
So thanks for not hanging on to those fossilized skulls and fragments to make summer movie props out of, and for leaving them to their proper place in museums and our nightmares.

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