Ecological restoration map of olive-patterned qushi fish. Illustrated by Guo Xiaocong
BEIJING, Feb. 25 (Xinhua) -- The study of fish fossils in ancient times has been a hot area of continuous concern in the paleontological community and has long attracted considerable attention. A new research result of the Chinese team of scientists has been found in Qujing, Yunnan Province, a new genus of the armor fish Ducknose family 410 million years ago, named "Olive-veined Qushi Fish", becoming the most primitive member of the currently known duck-kissed fish family.
Key Material: Explores armored fish adaptation to radiation
The reporter learned from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (Institute of Paleovertebrates of the Chinese Academy of Sciences) on the 25th that Gai Zhikun, Zhu Min, Jiang Wenyu of Shandong University of Science and Technology, Shi Xiaodong, Li Qiang and other researchers of Qujing Normal College cooperated to study and find "olive-patterned qushi fish" in the fossils of armor fish in the Xu Jiachong group in the early Devonian period of Qujing (about 410 million years ago), and the result paper has recently been published online by the international academic journal "Historical Biology".
Phylogenetic relationships and phylogenetic classification of suborder armorfish. Courtesy of Gai Zhikun
The corresponding author of the paper, Gai Zhikun, an associate researcher, said that the newly discovered and named "Olive Pattern 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 (Qushi) to thank the school for its contribution to the protection of the "Qujing Ancient Fish Kingdom".
He said that the discovery of the "olive-grained curved fish" enriched the morphological characteristics of the armor fish, providing a key material for exploring the adaptive radiation of the armored fish in the Early Devonian Prague period, and the "olive-grained curved fish" was also of great significance for studying the origin, diversity and paleogeographic distribution of the duck-kissed fish family.
Important role: understanding the transition from jawless to jawed
According to Gai Zhikun, armor fish are an extinct "armor-wearing" armor fish, which has only been found in the Silu-Devonian strata of China and northern Vietnam so far, with a strong indigenous color. In the systematic classification of vertebrates, armorfish are currently considered to be sister groups of bony beetlefish + jawed, which is very important for understanding the transition of vertebrates from jawless to jawed.
Traditional morphological analysis suggests that armorfish are a class of benthic fish with weak swimming ability because they have a flattened dorsal and ventral head armor, the eyes located on the back of the cephalic carapace, and the mouth on the ventral surface of the cephalothorax. 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.
For example, the sword crack turtle discovered by the research team in Zhaotong, Yunnan in 2015 is the first armor fish with a streamlined body shape, indicating that some armor fish may have greatly enhanced their swimming ability and have begun a self-swimming lifestyle, thus having a more active feeding behavior.
Olive-patterned composer fish head beetle fossil photograph and its restoration. Illustrated by Guo Xiaocong
New Clues: Clarifying the Uncertainty of the Duckfish Family
Gai Zhikun pointed out that the duck-kissed fish family belongs to a very interesting taxon under the suborder Armorfish suborder South China fish, named because its model genus Duck-kissed fish has a duck-billed snout. Among the armorfish, the ducknose family is of great significance for understanding the ecological diversity of the early Devonian Bragg period armor fish, however, there are still many uncertainties in the current academic understanding of the duckfish family, due to the scarcity of fossil material, especially the model genus Ducknose genus with only one missing incomplete specimen of the posterior head nail.
Previously, some scholars speculated that the head carapace of the duck-kissed fish and the Umeng mountain fish of the duck-kissed fish family may belong to the "tricho-type", with backward-extending horns and inner horns. Other scholars believe that the horns and inner horns of duckfish and Umong mountain fish 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.
The discovery of the "olive-veined curved fish" provides new clues to clarify the above uncertainties and related controversies: the main features of this new genus are the proximate fork shape of the cephalic carapace; the developing horns and inner horns; the oval shape of the middle dorsal foramen; the sensory tube phylogenetic; the lateral edge of the cephalic nail is smooth and not parallel; 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.
Developmental analysis: identification of the most primitive members of the family Ducknose
The first author of the paper is Jiang Wenyu, an undergraduate student of Shandong University of Science and Technology who participated in the 2019 "Science and Technology Innovation Plan" of the Institute of Paleovertebrates of the Chinese Academy of Sciences, she said that in order to explore the systematic location of the "olive-veined Qushi fish", the scientific research team expanded the previous matrix data, in addition to the Qushi fish, but also added split turtles from the Zhaotong Po Songchong Formation in Yunnan in the same period, and used the branch systemological method to analyze the phylogenetic relationships of armor fish.
The results of phylogenetic analysis showed that the Qushi fish, the duckfish, the Umong mountain fish and the split turtle together formed a monophyletic family, the ducknose fish family, so the research team classified the qushi fish into the duckfish family. The new branching system diagram shows that the Qushi fish forms a sister group with all other species of the duckfish family, and the Qushi fish represents the most primitive member of the currently known duckfish family.
Jiang Wenyu believes that the discovery and research of the "olive-patterned curvature fish" shows that the original members of the duck-kissed fish family had a complete abdominal ring, an unbending gill cavity, and a backward extension angle and inner horn. Unlike the cracked turtle with strong swimming ability, like most armored fish, the qushi fish may still be a benthic fish, moving on a coastal, marine environment, sandy or muddy base, which will also provide new clues to the evolution of duck-kissed fish. (End)
Source: China News Network