The post Fascinating New Findings at Ashfall Fossil Beds appeared first on A-Z Animals.
Since the 1920s, people have been finding fossils near Verdigre Creek in northeast Nebraska. However, it wasn’t until 50 years later that scientists discovered the site known as the Ashfall Fossil Beds. Geologists believe this mass graveyard was caused by the powerful eruption of a volcano in the system that lies beneath Yellowstone — hundreds of miles away.
Scientists have found the fossils of 18 species of vertebrates, including birds, reptiles, canines, camels, horses, and rhinoceroses. The smaller animals were the first to die, quickly suffocating under the foot of ash that blanketed the area. Animals with larger lungs lived longer, but they, too, were eventually killed by the ash. The last animals to die were Teleoceras major, an extinct genus of rhinoceros. Over 100 Teleoceras major skeletons have been found, which is far more than any other species. However, why were there so many? Were they fleeing the ash, or were they just in the wrong place at the wrong time? A recent study by researchers from the University of Cincinnati and the University of Nebraska has the answer.
What Is Teleoceras Major?
The Teleocerus major skeletons at Ashfall Fossil Beds are estimated to be 11.83 million years old.
Teleoceras major was a large, stocky mammal with short legs, a barrel-shaped body, a small horn, and large incisors, or tusks. It was thought to stand 3.5 feet at the shoulder and reach weights over 2,000 pounds. Native to North America, Teleoceras major was once a common sight across the Great Plains. The animals unearthed at the Ashfall site lived during the Clarendonian North American Land Mammal Age 12.5-10 million years ago.
Although it is classified as part of the Rhinocerotidae group, Teleoceras major skeletons indicate it looked much different from modern rhinoceroses. It had shorter legs and a shorter horn, making it look more like a hippopotamus. Whether Teleoceras major was semi-aquatic like modern hippopotamuses has been debated for over a hundred years. However, Clark Ward, lead author and researcher at the University of Minnesota, found that Teleoceras major from Ashfall was most likely semi-aquatic.
“Before I started my projects, I did not think they would be semi-aquatic. I thought that they could have been mud-loving or maybe only sometimes visited water to cool down, but I didn’t expect them to seem like they spent much of their time in the water,” shares Ward. “I was very surprised to see that Ashfall was so different from most other Teleoceras fossil localities! It raises a lot of questions about the diversity of Teleoceras behavior and their adaptability to different environments through time and across the continent.”
As one might predict, research demonstrates Teleoceras major at Ashfall were herbivores. They foraged on grasses and herbaceous dicots (a type of flowering plant) found in wetter environments.
What Were Researchers Looking For?
The researchers’ goal was to investigate different types of movement in Teleoceras major at Ashfall Fossil Beds. Sexual dimorphism, specifically the males’ longer, sharper tusks, suggests a polygynous mating system where males fought for mating privileges. That led researchers to believe that juvenile males left their birth range to establish their own permanent ranges. The authors reasoned that seasonal migration and long-distance movement in response to volcanic eruption were also possible.
To explore the problem, researchers analyzed isotopic ratios for strontium, oxygen, and carbon in the enamel of the animals’ fossilized teeth.
“Oxygen isotopes are generally related to water and how wet or dry an area was. Strontium isotopes are related to the underlying soil and where an individual was foraging. Animals take up strontium from the vegetation they eat, and the plants get strontium from the soil,” Ward explains. “As an animal eats plants from different types of soil, they take up different ratios of strontium isotopes, which we can then measure in the lab and use to investigate how an animal moved through life.”
Analyzing carbon in the animals’ enamel allows researchers to reconstruct the carbon in the environment. Carbon isotope data indicate what kinds of vegetation grew there. This can distinguish animals by their diets or the different habitats in which they foraged.
The Surprising Results
Researchers analyzed the enamel on the animals’ fossilized teeth to determine the extent of their mobility.
Unexpectedly, researchers found no evidence that the surveyed animals migrated or that they had fled the disaster. Nor was there any evidence that they dispersed once young males reached maturity. Instead, there was compelling evidence that Teleoceras major lived a more sedentary lifestyle than researchers had predicted. The study’s authors discovered that isotopic data were consistent with the animals at Ashfall having limited mobility throughout their lives. So, all of these animals are believed to have been locals.
A warm, stable climate is thought to have made it possible for such large groups of hooved animals to remain in the same area all year. The results suggest semi-aquatic adaptations would have limited Teleoceras major‘s movement, keeping the animals close to the waterhole at Ashfall or other nearby water sources.
Ward notes, “We showed that Teleoceras major probably was not very mobile and tended to forage in one place during life. This, for me, strongly suggested that they were semi-aquatic, because being tied to the water would limit how far you can roam before you have to return.”
The authors mention that modern hippos gather in large herds during the dry season. They disperse during the wet season, but remain in the same water system. So, it’s possible Teleoceras major behaved in a similar manner.
I was very surprised to see that Ashfall was so different from most other Teleoceras fossil localities! It raises a lot of questions about the diversity of Teleoceras behavior and their adaptability to different environments through time and across the continent.
Clark Ward, lead author and researcher at the University of Minnesota
Researchers also theorize that Teleoceras major may have practiced social dispersal instead of spatial. They point out that modern white rhinos have been found to avoid inbreeding by selecting mates with genetic differences when neither sex disperses. It’s possible Teleoceras major had similar adaptations to ensure the genetic fitness of their offspring.
The Impact on Modern Animal Research
Strontium isotope ratios can assist modern researchers in understanding migration patterns and changes in landscape use in both extinct and living species. Ward highlights the importance of research on both fossil and living rhinoceroses. He stresses that three of five rhinoceros species are critically endangered and face extinction in our lifetimes.
“For Sumatran and Javan rhinos, there are more Teleoceras major discovered at Ashfall than their entire global populations. The scarcity of modern rhinoceroses limits research on these species, and therefore also limits our understanding of all rhino species, living and dead,” Ward emphasizes. “By studying fossil rhinos, I hope to expand our understanding of the rhinoceros family, while also not disturbing the very fragile and highly valuable populations of modern rhinos.”
The post Fascinating New Findings at Ashfall Fossil Beds appeared first on A-Z Animals.