China News Service, Beijing, August 30th (Reporter Sun Zifa) The Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (Institute of Paleoanthropology, Chinese Academy of Sciences), the Natural History Museum of London, UK, and the Natural History Museum of New York, USA, through cooperation, have jointly developed a study on the middle pygmy produced in the United Kingdom. Research on the fossils of alien beasts (thieves, polyglotdons) at Woodeaton, a new location in Luo Shi (about 168 million years ago), to determine and discuss the long-standing morphological and classification problems of the thieves. The homology of the tooth characteristics of alien beasts was also analyzed for the first time at the species level of known thieves.
This important research paper on the evolution of extinct ancient animals, which was recently completed by the three institutions of China, the United States, and the United States, was published online in the Journal of Systematic Palaeontology, an international professional academic journal.
The upper and lower dentitions on the left side of the three types of thieves were compared, and the teeth in the EF dentition were once classified into four genera.
Photo courtesy of the Institute of Ancient Spine, Chinese Academy of Sciences
Mao Fangyuan, the first author of the paper and a researcher at the Institute of Ancient Spine of the Chinese Academy of Sciences, accepted an interview with a reporter from China News Agency on the 30th and said that the modern concept of alien beasts includes polycystic tooth beasts, thieves beasts and Gondwana beasts.
Among them, thieves are the earliest reported Mesozoic mammal fossils, which were recorded in 1847, and the earliest polytumorous mammals were reported in 1857. In the study of Mesozoic mammals, these two are also the two most controversial. taxa, the controversy dates back at least to Owen's 1871 monograph and continues to this day.
The reasons for their controversy are that one is the strange shape of the alien beasts, and the other is that the fossils are preserved and broken, especially the fossils of thieves. Before the report of the thieves in the Yanliao biota, they were basically single tooth specimens or broken jaws , so that the academic community has very limited understanding of them, and it is obviously problematic to discuss their evolution and phylogenetic relationships on this basis.
She pointed out that in the past ten years, well-preserved fossils of thieves have been found in the Yanliao biota in China, which has provided new key fossil evidence for related research and greatly enriched the academic community's morphological and biological understanding of thieves. content awareness.
However, in the early European related studies, the remaining problems in the identification of fossils have not been properly revised before. Although these specimens in Europe are incomplete, they are useful for understanding the evolution of alien beasts in terms of age, geographical distribution, and morphological diversity. Of great significance: the earliest thieves were found in the Late Triassic (about 220-200 million years ago) strata in Europe, and the earliest and exact polydactyloids were found in Europe, Siberia and China in the Middle Jurassic , their understanding involves the origin and early evolution of mammals and high taxonomic phylogenetic relationships.
In this study, the collaborative team established two new genus and new species of thieves based on new specimens from the Middle Jurassic in the United Kingdom, named "Butlerodon" and "Kemacodon", which were between the Late Triassic and European The transitional characteristics between the Middle Jurassic Forest Marble Formation species and the Middle and Late Asian Jurassic species are of great significance for understanding the continuous evolution of thieves.
At the same time, the collaborative study also found a specimen of the upper teeth of a polytumoral tooth, which is one of the earliest known representatives of a polytumoral tooth.
The fossil record from this site in the United Kingdom once again shows that Jurassic thieves and the earliest polydactyloids coexisted in the fauna of Europe, Siberia, and East Asia, and existing fossils show that in these earliest alien assemblages , the fossil abundance and genus diversity of the thieves are higher than those of the polytus.
Mao Fangyuan said that the cooperative team also systematically determined the British exotic animal specimens reported in the early years in this research paper, which involved complex classification issues, including the replacement of occupied genus names, and the identification of thieves and multi-tumor teeth respectively. The dental specimens of 4 genera were merged, and the dentition morphology of the merged species was reinterpreted and reconstructed.
On this basis, the cooperative team conducted a comprehensive discussion on the occlusion and homologous structure of the teeth of the known thieves, and based on the characteristics of the teeth, the first phylogenetic analysis of the known species of thieves was conducted.
The results of the analysis show that the alien mammals in the Middle Jurassic in Europe are closer to those in Asia; the thieves, like the polytubeled mammals and mammals, were distributed globally in the Mesozoic.
She believes that these new morphological contents and phylogenetic relationships of alien beasts, as well as the related geohistory and paleogeographic distribution, can provide new evidence for understanding the origin and differentiation process of mammals.
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