Scientists reclassify two fossil specimens found in Texas.
Beardogs — a strange group of extinct mammals that first appeared on the scene around 40 million years ago — are neither bears nor dogs, but they resemble, and are distantly related to both. According to a study published in Royal Society Open Science, two fossil specimens from Texas have now been welcomed into the beardog clan.
Susumu Tomiya, a postdoctoral scholar at The Field Museum in Chicago, was digging around in the museum’s collections when he stumbled upon something unusual. "There were beautiful jaws of a small carnivore, but the genus the specimen had been assigned to didn't seem to fit some of the features on the teeth,” he recalls in a press release. “It made me suspect that it belonged to a very different group of carnivores."
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The specimen had previously been classified as Miacis, a primitive group of carnivores that lived during the Eocene. But to Tomiya, the upper teeth didn’t seem quite right. "The fact that these teeth appear to have been well adapted for crushing suggests that these animals were eating more than just meat — they may well have branched out into other foods like berries and insects, like small foxes do today," he says.
These subtle features more closely resembled those of beardogs, which appeared during a later periods than Miacis.
Tomiya located a second fossil that was also classified as Miacis at the University of Texas at Austin, which had similar teeth those belonging to the first specimen.
Using high-resolution X-ray CT scans, Tomiya and his coauthor Jack Tseng of the University at Buffalo digitally reconstructed the skull of the Texas specimen. The internal features of the skull demonstrated additional similarities to beardogs. Among other finds, the scans revealed deep, bone-enclosed space in the animal’s ear, which is characteristic of members of the beardog group.
The findings confirmed that the specimens previously classified as Miacis were in fact beardogs.
"These are some of the earliest beardogs — they lived 38 to 37 million years ago," says Tomiya. Although these early specimens were only around the size of a Chihuahua, over time the lineage gave rise to predators that were larger than modern-day lions.
"Our research pinpoints the southwestern US as a key region in understanding the diversification and proliferation of this once successful group of predators prior to their extinction millions of years ago," says Tseng.
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