Source: CCTV news client
Recently, the Chinese Academy of Sciences vertebrate paleontology and paleoanthropology research institute, Shandong University of Science and Technology and Qujing Normal University and other scientific research teams, in Qujing, Yunnan Province, the early Devonian Prague period (about 410 million years ago) discovered a new genus of armor fish ducknose family: olive-grained qushi fish. The species name indicates that the surface of its head nail is covered with unique olive tumor spots, and the genus name is given to Qujing Normal College in appreciation of the contribution of the Qushi Natural History and Culture Research Center in protecting the "Qujing Ancient Fish Kingdom". The discovery of the olive-grained croaker has enriched the morphological characteristics of the armor fish, provided a key material for exploring the adaptation radiation of the armor fish in the Early Devonian Prague period, and was also of great significance for the study of the origin, diversity and paleogeographic distribution of the duckfish family. This achievement was recently published in the international academic journal Historical Biology.
The armorfish is an extinct class of "armor-wearing" armorfish that has so far only been found in the Silu-Devonian strata of China and northern Vietnam, with a strong indigenous color. In the systematic classification of vertebrates, armorfish are currently considered to be sister groups of "bone beetles + jawed", which is very important for understanding the transition from jawless to jawed by vertebrates. Traditional morphological analysis suggests that armored fish are a group of benthic fish with weak swimming ability because they have a flattened dorsal and ventral head, eyes located on the back of the head, and an opening on the ventral surface of the head nail. However, recent hydrodynamic analyses based on armored fish head armor have shown that armored fish have the potential to have a wider range of lifestyles and ecological diversity, with greater mobility and flexibility, as are bone-beetle fish.
△ Olive pattern composer fish head beetle fossil photo and its restoration
The family Ducknose belongs to a very interesting taxon of the suborder Armorfish in the order South China , named after the model genus Duckfish with a duck-billed snout. Among the armor fish, the duckfish family is of great significance for us to understand the ecological diversity of the early Devonian Bragg period armor fish, such as the sword crack turtle found in Zhaotong, Yunnan in 2015, which is the first armor fish with a streamlined body shape, indicating that some armor fish may have greatly enhanced their swimming ability and begun a self-swimming lifestyle, thus having a more active feeding behavior. However, there is still a lot of uncertainty about our understanding of the genus Ducknose, due to the scarcity of fossil material, especially the model genus Ducknose, which has only one missing incomplete specimen of the posterior head carapace. In the original description, some authors speculated that the head beetles of the ducksnose and ummon in the family Duckfish may belong to the "trichodermic type" with backwards-extending horns and inner horns. However, other authors have suggested that the horns and inner horns of ducksnose and ummon may be secondary and missing, belonging to the "split turtle type". In addition, the homology of some sensory tubes of ducksnoses with those of other known armorfish is also controversial. Therefore, any information that will help us understand the morphology of the duckfish family will help us clarify these issues.
△ Ecological restoration map of olive-grained qushi fish
The discovery of the olive-patterned quercus provides new clues to our clarification of these problems. The main features of the new genus are the proximate fork of the cephalic nail, the developmental and inner angles, the oval shape of the middle dorsal foramen, the sensory tube phylogenetic, the smooth and not parallel lateral edge of the cephalothorax, and the ornamentation composed of olive-shaped central tumors. The morphology of the head of the Trichoderma is very similar to that of the trichodermidae, but differs from the middle dorsal foramen of the crescentaceae of the trichodermidae, which is considered an important distinguishing feature of the trichocosaur family. Therefore, in the shape of the middle back hole, the qushi fish is closer to the duckfish. In order to explore the systematic location of the Qushi fish, the researchers amplified the previous matrix data. In addition to the Qushi fish, the split turtles from the Po Song Chong Formation in the same period were also added, and the phylogenetic relationships of armor fish were analyzed using the branch systemology method.
Phylogenetic analysis results showed that the Qushi fish, duck-kissed fish, Umong mountain fish and split-snapped turtles together constituted a monophyletic family, the duck-kissed fish family. Therefore, the Qushi fish can be classified as a duckfish family. The new branching system diagram shows that the Qushi fish forms sister groups with all other species of the duckfish family. Thus, the Qushi fish represents the most primitive member of the currently known duck-kissed fish family. This suggests that the original members of the duck-kissed fish family had intact abdominal rings, unbending gill cavities, and extending backwards and inner horns. Unlike cracked turtles, which have strong swimming ability, like most armored fish, the qushi fish may still live in benthic life, moving on the coast, in the sand of the marine environment, or on a muddy base. Therefore, the discovery of new materials provides new clues for the study of the evolution of duck-kissed fish. (CCTV reporter Shuai Junquan)