Scientists have found the most complete fossil of an early Cretaceous mammal in history

Source: China News Network

The reporter learned from Yunnan University on the 14th that Bi Shundong, a professor at the Key Laboratory of Paleontology Research in Yunnan Province, led the Sino-US paleontology research team and found the most complete preservation of early Cretaceous mammal fossils so far, named mixed element beasts. This scientific research result, published online in the British journal Nature on the 13th, drew a new conclusion that Chinese possums belong to the true mammals, and suggested that Asia may not be the origin center of marsupials.

The newly discovered specimen of mixed element mammals was found in the lower strata of the Yixian Formation in the Ningcheng region of Inner Mongolia, and is a mammal in the Rehe biota dating back 126 million years, with well-preserved and exquisite structure. Using high-precision CT scanning technology, the researchers digitally reconstructed the fossil bones embedded in the rock in three dimensions, basically restoring the morphological characteristics of each bone.

On this basis, the research team also spent 3 years to construct a large data matrix including 56 early mammal taxonomy units and more than 400 morphological features, establishing a reliable early mammalian lineage tree.

Phylogenetic analysis showed that the hybrids were an early type of euphropods (placenta and their ancestors), and at the same time developed mixed characteristics of euphropods and post-mammals (marsupials and their ancestors). All 4 species of mammals in the Rehe biota belong to the euphropod class, including the Chinese possum, which was previously classified as a post-mammal.

The scientific significance of this study is that the Chinese possum is a true mammal and suggests that Asia may not be the center of origin of the marsupial. At present, the earliest known fossil record of marsupials is that of a triangular toothed beast found in North America 110 million years ago.

In addition, for the first time, the mesozoic mammals have preserved the complete hyoid bone organs of the Mesozoic mammals. The hyoid organs hang between the skull and the laryngeal knot, and since they do not form joints with any other bone, they are difficult to preserve in fossils and are the least known bones in mammalian bones. This discovery may bring new enlightenment to the study of many fields of biology and medicine. (Reporter Hu Yuanhang)