300 million-year-old giant shark swam the Texas seas

DALLAS — Even sharks are bigger in Texas.

Around 300 million years ago, predatory “supersharks” that stretched about 8.5 meters long — the length of a limousine — prowled the warm, shallow seas of what is now Texas. Today’s biggest predatory sharks, such as great whites and tiger sharks, top out at around 6 or 7 meters in length.

Scientists have found fossils from big, ancient sharks before, but none this old, paleontologist John Maisey said October 16 at the Society for Vertebrate Paleontology annual meeting. “You don’t see sharks this size again until the Cretaceous,” he said — roughly 200 million years after the Texas shark lived.

Except for teeth, shark remains don’t show up much in the fossil record. That’s because shark skeletons aren’t made of

easy-to-preserve bones. Instead, protein fibers connect bits of mineralized cartilage, like glue cementing tiles in a mosaic. When sharks die, the fibers break down, leaving behind unconnected pieces.

Remains of the Texas shark rested in an area that was once home to corals, clams, mollusks and bony fish, said Maisey, of the American Museum of Natural History in New York City. He and colleagues used fragments from the back of the shark’s head to calculate skull size: about 85 centimeters, or roughly the length of a 2-year-old child. The team then used skull size and what they know about the body proportions of other ancient sharks to estimate the Texas shark’s total length.

The fossil shark may be related to Glikmanius, an extinct shark with a long body and forked tail that lived around the same time, but scientists will need to examine more specimens to say for sure.