Newly Discovered Dinosaur-Era Creatures Offer Insight Into Evolution

Fossils of Fossiomanus (left) and Jueconodon

By Lida Tunesi

Graduate Center Professor Jin Meng (Earth and Environmental Sciences) was part of a team that recently discovered two new species of small, mammal-like creatures from 120 million years ago. The fossils came from northeastern China.

The new animals are the first so-called “scratch-diggers” found in this area, and share similar digging-oriented traits even though they are not closely related.

“We depend on fossils to understand the early evolution of mammals and other organisms,” Meng said, “so that we can understand what has happened in Earth’s history and why there is such diverse life.”

Jin Meng in the fieldMeng, who also serves as curator-in-charge of fossil mammals at the American Museum of Natural History, studies early mammals from the Paleogene period and Mesozoic era. He and his co-authors described the new findings in a paper published in Nature.

One of the creatures, dubbed Jueconodon cheni, is a mere seven inches long and belongs to a now-extinct group of mammals called eutriconodontans. The other, named Fossiomanus sinensis, is about a foot long. Though technically a reptile, Fossiomanus does fall into the broader category of mammaliamorpha. The two lived during the Mesozoic era, more commonly known as the age of the dinosaurs.

Jueconodon and Fossiomanus also share some features that are characteristic of burrowing animals, like short tails and relatively short hindlimbs compared to their forelimbs. They were likely scratch diggers, the researchers concluded, meaning they used their front claws to bore into the ground.

This finding is notable for two reasons. First, Jueconodon and Fossiomanus were not closely related, so the fact that they developed such similar, specialized features is an unusual example of convergent evolution. Second, they are the first known scratch-diggers among all the creatures from this region and time period, collectively known as the Jehol Biota.

The fossils also showed that both animals had unusually large number of vertebrae, which the researchers hypothesized could have been due to genetic mutations during early development.

“These fossils shed light on the evolutionary development of the axial skeleton in mammaliamorphs,” the authors wrote, “which has been the focus of numerous studies in vertebrate evolution and developmental biology.”

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Submitted on: MAY 27, 2021

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