Hundreds of thousands of years in the past in Nebraska, chunky, stumpy-legged rhinoceroses had been social gathering animals, crowding collectively in big herds at watering holes and rivers.
Chemical signatures within the fossilized tooth of the extinct, corgi-shaped beasts recommend they didn’t roam extensively, as an alternative forming massive, native herds in contrast to the extra solitary rhinos of at present, researchers report April 4 in Scientific Reviews.
About 12 million years in the past through the Miocene Epoch, the Yellowstone supervolcano erupted and coated a lot of North America in ash. Round a watering gap that ultimately grew to become Nebraska’s Ashfall Fossil Beds State Historic Park, a couple of foot of the particles fell on the panorama.
“It will have been like a nasty mud storm,” says Clark Ward, a paleontologist on the College of Minnesota in Minneapolis.
The ash slowly suffocated and starved the native fauna, with many perishing within the watering gap and fossilizing. Researchers have since uncovered about 2 hundred animal skeletons on the web site, together with over 100 largely full skeletons of Teleoceras, an historic, barrel-bodied member of the rhinoceros household.
As a result of Teleoceras had the roly-poly proportions of a hippopotamus, the herbivores have been generally envisioned as equally semiaquatic. However current analysis had referred to as this amphibious life-style into query, Ward says. It additionally wasn’t clear if Teleoceras’ had wealthy social lives, or in the event that they had been largely solitary like trendy rhinos.
To assist reply these questions, Ward — then on the College of Cincinnati — and his colleagues wished to know if the rhinos and different animals that died at Ashfall had been migrants that gathered there, or in the event that they had been locals. The group took samples of 13 fossil rhinos’ molars, chemically analyzing them and evaluating ratios of various types of oxygen, carbon and strontium. Carbon ratios point out what kinds of grasses the traditional rhinos’ ate in life, and oxygen ratios can inform researchers about seasonal adjustments the animals skilled. Collectively these can reveal particulars in regards to the animals’ weight loss plan and habitat.
Moreover, ratios of various types of strontium are tied to particular geographic areas, permitting researchers to see if historic animals traveled between areas, says Danielle Fraser, an evolutionary biologist on the Canadian Museum of Nature in Ottawa who was not concerned with the analysis.
The group discovered little or no variation within the carbon and strontium ratios, suggesting Teleoceras was largely a homebody that wallowed and fed proper round Ashfall. This may increasingly additionally imply the plentiful rhino stays at Ashfall are the results of lives lived in big herds dozens of animals robust.
Ward was a bit shocked that there wasn’t proof the rhinos had been shifting between completely different areas.
“I suspected younger males to journey far distances searching for mates, possible having to attempt to attempt once more,” he says. Mating solely inside their house herds could have raised the possibilities of inbreeding, so it’s attainable the rhinos intermingled with the herds subsequent door to keep away from this danger.
The findings additionally present insights into the traditional Ashfall ecosystem, Fraser says. If the rhinos didn’t should migrate to different areas, it suggests they’d have had entry to sufficient meals and water year-round.
Ward says he and his colleagues had been puzzled by what number of rhinos, horses and camels residing in the identical place may coexist with out stripping the world naked of vegetation. It’s attainable the hotter local weather of the Miocene led to extra productive vegetation. Or, Ward says, the herbivores’ presence boosted plant progress as they cleared out older vegetation and deposited manure.
