Fossilized feces help confirm the diet of extinct ‘bone-crushing’ dogs

Xiaoming Wang, vertebrate paleontology curator for the Natural History Museum of Los Angeles County, has studied extinct “bone-crushing” dogs for most of his career.

These ancient canines lived throughout North America about 6 million years ago, and their powerful, heavyset jaws earned them their — totally metal — nickname. They’re unlike any dogs or wolves we see today, but they do have something in common: They pooped. And for the first time ever, NHMLA researchers have managed to find some of their very old, very fossilized feces.

Coprolites — fossil poop — are exceptionally rare. Bones are more likely to be preserved than soft tissues or feces, and yet fossils of bones are still pretty hard to find. The 14 coprolites in this study — Jack Tseng, UB assistant professor of pathology and anatomical sciences, is senior author on the study — were found at a fossil site in central California where researchers have found lots of bones from the bone-crushing dog species Borophagus parvus, so that’s most likely who made them. And these fossilized feces have a lot to tell us, as gross as that may sound.

First, scientists can tell, based on how they were found at the fossil site, that the poops occurred in clusters from multiple individuals and multiple “dropping events,” which could mean that these dogs were marking their territories, a behavior we see today but has never been documented in extinct carnivores before.

And that’s just the most basic of the defecation information. Researchers haven’t gotten into them yet. These fossils still contain the partially digested bones of 6-million-year-old meals, such as a bird limb bone and a large mammal’s rib, among others. And while scientists can’t determine which exact species these dogs ate, they can estimate the rough size of the prey based on some of the bones’ measurements. From the looks of it, these bone-crushing dogs regularly dined on animals many times bigger than themselves, which suggests they were hunting in groups to accomplish this. Social hunting might also explain why they ate so much bone: If mealtime is a competitive sport, there’s really no time to pick and choose each bite carefully.

Bone-crushing dogs went extinct around the time the Ice Age was setting in, about 2 million years ago. The special bone-eating role they played in these ancient ecosystems was never replaced, so their absence may have had an outsized effect on the ecosystems they were a part of.

Discoveries like these coprolites help scientists get a clearer picture of what life was like and how ecosystems functioned long before humans arrived on the scene.

Not bad for some old poop.