Prehistoric Evidence Shows Mammals Evolved Rapidly When Dinosaurs Went Extinct

Three new species of ancient mammals have been found by scientists, indicating rapid evolution following the dinosaur extinction.

The finding of three new species of ancient animals from the birth of modern mammals is described in a study published today in the peer-reviewed Journal of Systematic Palaeontology. It suggests fast development shortly following the dinosaurs' catastrophic extinction.

Discovering New Species of Ancient Mammals

Miniconus jeanninae, Conacodon hettingeri, and Beornus honeyi are three new species to science. They range in size from a mouse to a rat-sized mammal that lived with the dinosaurs in North America to a modern house cat, far larger than the common mouse to rat-sized mammals that existed before it.

Each has its own set of distinguishing dental characteristics.

Due to seemingly inflated (puffy) molars, Beornus honey was named in honor of The Hobbit character Beorn.

The new species is part of a complex group of placental mammals known as archaic ungulates (or condylarths), the ancestral forerunners of today's hoofed mammals (e.g., horses, elephants, cows, hippos).

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Finding Fossil Pieces

Paleontologists at the University of Colorado in Boulder discovered fragments of the animals' lower jawbones and teeth, revealing their identity, lifestyle, and body size.

The three new species are members of the Periptychidae family, differentiated from other 'condylarths' by their enlarged premolars and unique vertical enamel ridges on their teeth. Researchers assume they were omnivores because they evolved teeth that enabled them to crush both plants and meat, but this does not rule out the possibility that they were strictly herbivores.

Because many kinds of mammals appeared for the first time shortly after the catastrophic extinction that wiped out the non-avian dinosaurs 66 million years ago, it is often regarded as the commencement of the 'Age of Mammals.'

Evolving After Dinosaurs Died

According to lead author Madelaine Atteberry of the University of Colorado's Department of Geological Sciences, "When the dinosaurs died out, mammals were able to thrive and diversify their tooth architecture quickly, as well as grow bigger bodies. As shown by the rapid emergence of new mammalian species following the mass extinction, they certainly took advantage of this chance."

Atteberry and co-author Jaelyn Eberle, a curator at the Museum of Natural History and a professor of geological sciences at the University of Colorado, examined the teeth and lower jawbones of 29 fossils 'condylarth' species to determine anatomical differences and used phylogenetic techniques to figure out how the species are related to one another and other early Paleocene species.

The evidence points to these three new species being discovered by science.

Beornus honeyi was the largest, about the size of a marmot or house cat; Conacodon hettingeri is similar to other Conacodon species but differs in the morphology of its last molar; Miniconus jeanninae is identical in size to other small, early Paleocene 'condylarths,' but is distinguished by a tiny cusp on its molars called a parastylid

Continuing Previous Studies

"Previous studies suggest that there was relatively low mammal species diversity across the Western Interior of North America in the first few hundred thousand years after the dinosaur extinction (what is known in North America as the early Puercan), but the discovery of three new species in the Great Divide Basin suggests rapid diversification following the extinction," says Atteberry. "These new periptychid 'condylarths' account for just a small portion of the site's more than 420 mammalian remains. Thus, we haven't fully captured the richness of animal diversity in the early Paleocene, and numerous more new species are expected to be discovered."

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