2021-10-14

The world’s oldest rib scale cleft toothed fish was found in Yunnan, the first in Asia

By yqqlm yqqlm

The world’s oldest rib scale cleft toothed fish was found in Yunnan, the first in Asia

Figure 1. Positive specimen and restoration of Asian rib scale cleft toothed fish (Xu Guanghui’s picture)

d002 41d5e07d0d8ff6facf3e02e237ba31b9 - The world's oldest rib scale cleft toothed fish was found in Yunnan, the first in Asia

Figure 2. About 250 million years ago, the most catastrophic mass extinction event at the end of Permian occurred in the history of life on earth. In order to understand the subsequent Triassic ecological reconstruction, Xu Guanghui’s research team has conducted continuous research on the Triassic marine strata in Yunnan Guizhou region of China for more than ten years, and successively discovered and named 21 kinds of aquatic vertebrate fossils. The Asian rib scale cleft toothed fish named this time was found in Luoping, Yunnan Province. It is a small nail eating fish with special scales. At present, only three fossils have been found in this ancient fish species, which is a rare species in Luoping biota 244 million years ago. Fortunately, they are well preserved and can completely restore their morphological characteristics, which provides important information for the study of bone morphology and phylogenetic relationship of costal scale cleft toothed fish family

The world’s oldest rib scale cleft toothed fish was found in Yunnan, the first in Asia(1)

Figure 3. Complete specimen of Asian rib scale cleft toothed fish (Photo by Xu Guanghui)

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Figure 4. The complete specimen of Asian costal scale cleft toothed fish (Photo by Xu Guanghui)

costal scale cleft toothed fish is a representative species of new fin fish trunks during the recovery of marine life in the Middle Triassic. The earliest fossil record was found in the marine strata at the junction of Italy and Switzerland 242 million years ago. The newly discovered Asian rib scale cleft toothed fish has advanced the earliest record of rib scale cleft toothed fish by about 2 million years, which has greatly increased people’s understanding of the biogeography of rib scale cleft toothed fish. It is difficult to determine the taxonomic position of costal scale cleft toothed fish because it has the transitional characteristics of costal scale fish and cleft toothed fish at the same time. Researcher Xu Guanghui, based on the detailed comparison and cladistic study of Eurasian costal scale cleft toothed fish, put forward the view that costal scale cleft toothed fish is a sister group of leaky lying fish for the first time, newly established costal scale cleft toothed fish family and classified it into leaky lying fish order. This research result not only solves the taxonomic problem of costal scale cleft toothed fish, but also has important significance for understanding the early evolution and biogeography of Triassic neofin fish

The world’s oldest rib scale cleft toothed fish was found in Yunnan, the first in Asia(2)

Figure 5. Restoration map of Asian rib scale cleft toothed fish (provided by Xu Yong)

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Figure 6. The newly reconstructed new fin fish branch pedigree shows the sister group relationship between costal scale cleft toothed fish family and leaky lying fish family (Xu Guanghui for the picture)

this study was supported by the National Natural Science Foundation of China and the strategic leading science and technology project of the Chinese Academy of Sciences