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Scientists have discovered two new species of burrowing ancestors of ancient mammals

A joint research team led by Dr. MAO Fangyuan and Dr. ZHANG Chi of the Institute of Vertebrate Paleontology and Paleontology (IVPP) of the Chinese Academy of Sciences and Professor Ming Jin of the American Museum of Natural History have discovered two new species of mammal-like animals that have lived in burrows for about 120 million years in what is known. Now in northeastern China.

New species, described in Temperate nature On April 7th, they bond closely. However, they independently developed traits to support their digging lifestyle. They represent the first “scratch diggers” discovered in this ecosystem.

“There are many hypotheses about why animals burrow into the soil and live underground,” said Professor Ming, the lead author of the study. To protect against predators, to maintain a relatively constant temperature, or to find food sources such as insects and plant roots. These two fossils are very unusual examples of animals that are not closely related, yet both have developed highly specialized characteristics of the digger. ”

Fossil mammal species – the ancestors of mammals – were discovered in Jehol Biota, which represents the early Cretaceous period, about 145 to 100 million years ago.

One of them is a mammal-like reptile called tritylodontid and represents the first of its kind to be identified in these organisms. About a foot in length, it has been named Fusiomanus sinensis. The other, Jueconodon cheni, Is eutriconodontan, a distant cousin of modern placental mammals and marsupials, which have been common in living organisms. It measures about seven inches in length.

Drill-adapted mammals have specialized digging traits. Researchers have found some of these hallmarks, including shorter limbs, strong forelimbs with strong hands, and short tail, in both. Fusiomanus And Juiconodon. In particular, these characteristics indicate a type of digging behavior known as “scratch digging,” which is accomplished primarily by the claws of the front limbs.

“This is the first convincing evidence of fossil life in these two groups,” said Dr. Mao. “It is also the first case of the excavators that we know of in Jehol Biota, which were home to a large variety of animals, from dinosaurs and insects to plants.”

The animals also share another unusual feature: an elongated spine. Typically, from neck to hip, mammals contain 26 vertebrae. However, Fusiomanus It had 38 paragraphs – a staggering 12 more than usual – during Juiconodon He was 28.

To try to determine how these animals obtained their elongated axial skeleton, paleontologists turned to recent studies in evolutionary biology, and found that the difference could be attributed to genetic mutations that determine the number and shape of the vertebrae during the early embryonic development of these animals. Variation in the number of vertebrae can be found in modern mammals as well, for example, in elephants, manatees, and elephants.

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The study was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, the Association for the Encouragement of Youth for Innovation, and the Calbash Fellowship at the Richard Gilder Graduate School of the American Museum of Natural History.

Contact: Doctoral Candidate at the Faculty of Medicine, University of Bergen, Inar Marius Hellstad Martinsen – Email – [email protected] – Cell phone – +4797788414

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