On June 14th, the internationally renowned academic journal Nature published the latest research results of Professor Zheng Xiaoting and Professor Wang Xiaoli of the School of Life Sciences (Institute of Geology and Paleontology) of Linyi University, "An Early CretaceousEutherian and the Placental–Marsupial Dichotomy", which were jointly researched by Indiana University and the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences.
Restoration of ambolestes zhoui (STM33-5).
In the form of a long article, the paper reports one of the best-preserved fossils of a Pre-Cretaceous mammal to date, named The Hybrid Beast. Mixed mammals are an early type of euphrasiacs (placenta and their ancestors) and develop a mixture of euphropods and post-mammals (marsupials and their ancestors). The study found that the previously reported Chinese possum and the mixed element beast belonged to the same branch, both early true beasts, not the ancestors of the marsupials. This important discovery reveals the complexity of the evolutionary process of mammals, changes people's understanding of the evolutionary history of the differentiation of different taxa of mammals, and makes people's understanding of the evolutionary history of mammals more and more clear.
The specimen of mixed element beast is preserved in the Tianyu Natural Museum of Shandong Province, from the lower strata of the Yixian Formation in Ningcheng District, Inner Mongolia, dating back to 126 million years ago, the Rehe biota is the most complete preserved paleontological fossil of the same era discovered so far, the earliest hyoid bone structure and ear eardrum ring were found, from which it was found to trace its living habits, living environment and ecological type, which is a paleontological fossil specimen of great significance.
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 spent 3 years to construct a large data matrix including 56 early mammal taxonomic units and more than 400 morphological features, establishing a reliable early mammalian lineage tree. Phylogenetic analysis showed that the four mammal species in the Rehe biota belonged to the euphropod class, including the Chinese possum, which was previously classified as a post-mammal. The scientific significance of this finding is significant. New conclusions that Chinese possums belong to the true mammals suggest that Asia may not have been the center of origin of marsupials, and that the earliest known fossil record of marsupials is that of a triangular toothed beast found 110 million years ago in North America.
Fig. 1 Specimen of Ambolestes zhoui (STM33-5).
In addition, for the first time, the mesozoic mammals have preserved the complete hyoid bone organs of the Mesozoic mammals. Suspended between the skull and the laryngeal knot, the hyoid bone is a series of slender bones that provide attachment to certain muscles of the tongue and neck, and are important organs for mammals to eat, chew and make sounds. Because they do not form joints with any other bone, they are difficult to preserve in fossils and are the least known of the mammalian bones. The human hyoid bone is composed of a single U-shaped bone, while the hyoid bone of the hybrid beast is composed of 7 bones, and its structure is more elaborate. As the reviewers point out: "These things would be widely used by others in the field". This discovery will bring new insights to the research of many fields of biology and medicine.
The genus name of the mixed element beast, which means that the yuan qi is not divided, the chaos is one, and the beginning of the yuan qi also refers to the special attributes of the creature that has the characteristics of the mixed characteristics of the real beast and the post-beast. The name of the species is Zhou Zhonghe, dedicated to Dr. Zhou Zhonghe, who thanked him for initiating and promoting the in-depth research of the Rehe biota, and for guiding and helping other young teams to conduct research on the Rehe biota.
The research was supported by the National Natural Science Foundation of China Basic Science Center project "Craton Destruction and Terrestrial Biological Evolution" and the National Natural Science Foundation of China.