Arthropods are one of the most successful animals on Earth since the Cambrian period, about 520 million years ago. They are the most familiar and common species, making up almost 80% of all animals today, more than any other species.
But how did arthropods evolve, and what did their ancestors look like? This is a big conundrum in the evolution of animals that has puzzled generations of scientists over the past century.
Now, researchers from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS) have discovered a 5-eyed shrimp-like fossil that provides important insights into the history of evolution. Initial chemistry of arthropods. Research is published in nature on November 4.
The Kylinxia fossils were collected from the Chengjiang fauna in southwestern China̵7;s Yunnan province. The fauna records the most complete early animal fossils of the Cambrian period.
Professor Huang Diying, corresponding author of the study from NIGPAS, said, “Kylinxia is a very rare chimeric species. It combines morphological features from different animal species, similar to ‘kylin’, a chimeric creature from traditional Chinese mythology. “
Professor Zhao Fangchen said: “Due to the very special taphonom condition, the Kylinxia fossils exhibit a sophisticated anatomical structure. For example, the nervous tissue, the eyes and the digestive system – these are the soft organs that we often cannot see in conventional fossils “author of study.
Kylinxia showed outstanding features of true arthropods, such as hard epidermis, segmented body, and articulated legs. However, it also integrates morphological features present in a very ancestral form, including the five singular eyes of Opabinia, known as the Cambrian “exotic wonders”, as well as iconic appendages. of Anomalocaris, a giant crest predator in the Cambrian ocean.
Among the animals in Chengjiang, Anomalocaris is the leading predator with a body length of up to 2 meters, and is considered the ancestral form of arthropods. But there is a huge morphological difference between Anomalocaris and actual arthropods. There is a large evolutionary gap between the two that can hardly be bridged. This void has become an important “missing link” in arthropod origin.
The research team conducted a detailed anatomical examination of the fossils of Kylinxia. They proved that the first appendages in Anomalocaris and arthropods were indeed homologous. Phylogenetic analyzes show that there is a relationship between the anterior Kylinxia appendages, the small anterior-mouth appendages of Chelicerata (a group that includes spiders and scorpions) and the beard of Mandibulata ( a subset of arthropods that include insects such as ants and bees).
“Our results indicate that the evolutionary site of Kylinxia is right between Anomalocaris and the true arthropod. Therefore, our findings have reached the evolutionary roots of real arthropods.” , Said Professor Zhu Maoyan, co-author of the study.
“Kylinxia represents an important transitional fossil predicted by Darwin’s theory of evolution. It narrows the evolutionary distance from Anomalocaris to actual arthropods and forms a” missing link “in the source. The origin of arthropods, contributes strong fossil evidence to the evolutionary theory of life, “said Dr. Zeng Han, the study’s first author.
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A species of early Cambrian arthropod with radioactive arthropod appendages, nature (Year 2020). DOI: 10.1038 / s41586-020-2883-7, www.nature.com/articles/s41586-020-2883-7
Provided by Chinese Academy of Sciences
Quote: A 520-million-year-old 5-eyed fossil revealing arthropod origin (2020, November 4) retrieved November 5, 2020 from https://phys.org/news/2020-11- million-year-old-five- eye-fossil-revelation-arthropod.html
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