Two extinct carnivorous predators had more in common than previously thought. Scientists from the American Museum of Natural History (AMNH) have found that a 20-million-year-old marine bear that resembled an otter, Kolponomos, likely had a powerful bite, similar to that of a saber-toothed cat, Smilodon.
Although these two prehistoric animals had very different food and habitat preferences, high-resolution X-ray imaging and computerized biting simulations revealed the predators shared similar jaw structure.
"Both of them have a distinctive profile with a deep jaw bone that tapers off toward the back, and both have an expansion of the mastoid processes and the skull's back surface, suggesting large attachment sites for muscles that let the animal move its head powerfully but with control," explained Z. Jack Tseng, a National Science Foundation and Frick Postdoctoral Fellow in the AMNH's Division of Paleontology, in a news release. "We definitely didn't expect to bring Smilodon into this study of feeding in a clam-eating marine carnivore, but that's what we ended up doing."
Only a few fossil teeth and skulls of Kolponomos individuals have been unearthed from ancient marine deposits along the Pacific coast of Oregon, Washington and, possibly, Alaska. With such a small number of fossils, not much is known about these rather elusive animals. In fact, their place in the evolutionary tree remains a mystery.
"When Kolponomos was first described in the 1960s, it was thought to be a raccoon relative," said Camille Grohé, also a National Science Foundation and Frick Postdoctoral Fellow in the AMNH's Division of Paleontology. "But later research on the skull base led some to think it might be a seal or a bear relative instead, and studies of its teeth show that they are very similar in both shape and wear to the teeth in sea otters."
Generally, sea otters crush their hard-shelled prey using their teeth. To better identify the bite style of Kolponomos, researchers conducted CT scans on the skulls of Kolponomos and six other carnivores: Smilodon, grey wolf, sea otter, river otter, brown bear and leopard.
Researchers found the jaw mechanics of Kolponomos and Smilodon are more similar to each other than to any of the other animals in the study.
"Our biomechanical data show that the chewing bites of sea otters and Kolponomos are not very similar," Tseng added. "They probably still have an overlapping diet based on tooth wear, but their evolutionary solutions for getting to those hard-shelled animals are dramatically different."
Researchers noted that their findings, recently published in the Proceedings of the Royal Society B, do not imply shared ancestry between Kolponomos and Smilodon, but rather the independent evolution of similar traits.
