75-Million-Old Mammal Species That Lived Alongside Dinosaurs Discovered

Palaeontologists in the US state of Colorado have discovered a remarkable fossil of a 'swamp dweller' who lived nearly 75 million years ago during the Age of Dinosaurs, also referred to as the Mesozoic era. The mammal, roughly the size of a muskrat, lived when Colorado was nothing more than an inland sea with the land surrounding it comprising of marshes and swamp land, according to a team of researchers at the University of Colorado (CU), Boulder who had been digging outside of Rangely for over 15 years.   

Led by CU's Jaelyn Eberle, the research has been published in the journal PLOS ONE. The discovery, which Eberle and her colleagues identified from a piece of jawbone and three molar teeth, has been named Heleocola piceanus.

The study stated that the morsel-sized mammal living in an ecosystem with tyrannosaurs, dromaeosaurs, oviraptorosaurs and ornithomimosaurs exhibited a "number of characteristics suggesting a diet more in line with plant-dominated omnivory". 

"In general, the molar morphology largely agrees with a plant-dominated omnivorous diet, with blunt crests, inflated cusps, and a low trigonid/talonid height differential," the study stated, adding that H. piceanus may have incorporated insects and/or small vertebrates into its diet along with roots, fruits, and nuts.

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'Holy cow'

John Forster, one of the co-authors of the study added that he first saw the bit of mammal jaw emerge from a slab of sandstone that he collected from the site in 2016. 

"I said, 'Holy cow, that's huge'," Foster, a scientist at the Utah Field House of Natural History State Park Museum in Vernal said. 

Meanwhile, Eberle said she was glad that discovery was made in Rangely, which sits in the northwest corner of the state, not far from Dinosaur National Monument. 

"It's a small town, but, in my experience as a paleontologist, a lot of cool things come out of rural environments," Eberle was quoted as saying by CU Boulder Today. "It's nice to see western Colorado have an exciting discovery. We have scientists that come from all over the world specifically to study our fossils. We really are lucky."

She added that the swamp dweller's size was actually relatively large compared to most Cretaceous period mammals.

"They're not all tiny. There are a few animals emerging from the Late Cretaceous that are bigger than what we anticipated 20 years ago."

The discovery of H. piceanus has added a new dimension to scientists and their understanding of mammalian life during the era when non-avian dinosaurs roamed the Earth before being wiped out by an asteroid 66 million years ago.