Aug. 18 (UPI) -- Mammals were mostly an afterthought during the age of the dinosaurs. For 150 million years, reptiles dominated the planet.
But the discovery of three new prehistoric mammal species, described Wednesday in the Journal of Systematic Palaeontology, suggests that mammal evolution began to accelerate shortly after the dinosaurs disappeared.
Remains of the three new species -- Miniconus jeanninae, Conacodon hettingeri, and Beornus honeyi -- were unearthed from an early Paleocene deposit in Wyoming's Great Divide Basin.
All three species are condylarths, early relatives of ungulates -- modern hoofed animals that include horses, elephants, cows and hippos.
The trio belongs to the Periptychidae family, which is distinguished from other condylarths by their large, swollen molars and puffy cheeks.
Scientists were able to distinguish the three new species, as well as gain insights into their ecologies, by studying differences in their dental anatomy. Researchers also used phylogenetic techniques identify the taxonomical relations between the three new species and related condylarths.
Paleontologists named Beornus honeyi for a bear-like character from "The Hobbit," characterized by its large cheeks. B. honeyi was the size of a house cat, dwarfing other early mammals, most of which were no larger than a rat.
Though it's not clear whether these early mammal species were herbivores or omnivores, scientists suggests their large premolars would have helped them grind hard-to-digest plant matter.
"When the dinosaurs went extinct, access to different foods and environments enabled mammals to flourish and diversify rapidly in their tooth anatomy and evolve larger body size," lead author Madelaine Atteberry from the University of Colorado said in a press release.
"They clearly took advantage of this opportunity, as we can see from the radiation of new mammal species that took place in a relatively short amount of time following the mass extinction."
The discovery of the three new archaic ungulates suggests mammal diversity dramatically increased in the millennia after the extinction event that defines the Cretaceous-Paleogene boundary.
"Previous studies suggest that in the first few hundred thousand years after the dinosaur extinction ... there was relatively low mammal species diversity across the Western Interior of North America, but the discovery of three new species in the Great Divide Basin suggests rapid diversification following the extinction," Atteberry said.
"These new periptychid condylarths make up just a small percentage of the more than 420 mammalian fossils uncovered at this site.
"We haven't yet fully captured the extent of mammalian diversity in the earliest Paleocene, and predict that several more new species will be described."