A 520 Million-Year-Old, 5-Eyed Fossil Reveals Origin of Arthropods

Holotype of Kylinxia zhangi. (Photo by D.-Y. Huang & H. Zeng)

(CN) — An extinct shrimp is set to make a big splash in the world of evolutionary biology.

Researchers introduced the world to the Kylinxia zhangi in a study published Wednesday in the scientific journal Nature. They called the specimen a link between extinct, close relatives of arthropods and their modern-day ancestors.

The study authors named the Kylinxia zhangi arthropod after the mythical chimera for its unique traits.

In Chinese mythology, the qilin is depicted as an armored ox creature with dragon-like features, while in Greek mythology the chimera is a fire-breathing lion and goat creature that is sometimes depicted having a snake for a tail.

While the extinct shrimp might not have spit fire, it did have praying mantis-like frontal appendages that could have been used to grab prey. It also boasted five eyes on stalks atop its head, according to study authors.

The wide world of arthropods includes extinct trilobites, scorpions, crabs, spiders and butterfly and a broad definition would cover any invertebrate animal with jointed appendages, a segmented body and an exoskeleton.

Kylinxia zhangi had all of that and more.

Ecological reconstruction of Kylinxia zhangi. (Artwork by D.-Y. Huang & H. Zeng)

“Kylinxia represents a crucial transitional fossil predicted by Darwin’s evolutionary theory,” lead author Dr. Zeng Han with the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (NIGPAS) said in a statement. “It bridges the evolutionary gap from Anomalocaris to true arthropods and forms a key “missing link” in the origin of arthropods, contributing strong fossil evidence for the evolutionary theory of life.”

The K. zhangi boasts traits from multiple arthropods and dates to the early Cambrian period, around 541 to 485 million years ago and fossilized specimens were discovered in the Maotianshan Shales, a series of Early Cambrian deposits in the landlocked province of southwest China.

Researchers say K. zhangi is a bridge between true arthropods and the extinct order Radiodonta, which were some of the largest predators during the Cambrian period.

An evolutionary breakdown also shows overlap with appendages in front of its mouth, which are commonly found in sea spiders, arachnids and other extinct arthropods. There’s also similarity with antennae of insects like bees, driving home the theory that K. zhangi will provide critical insight into the evolutionary and biological relationship between early arthropods.

The K. zhangi findings are an example of a transitional fossil, one that shows traits of an extinct group and its descendants. The findings from the K. zhangi research fills in a key missing link that has eluded researchers.

Study co-author Dr. Zhu Maoyan from NIGPAS said the research places K. zhangi between the extinct Anomalocaris, a 3-foot shrimp-like predator, and other arthropods.

“Therefore, our finding reached the evolutionary root of the true arthropods,” Maoyan said in a statement accompanying the study. The study authors did not immediately respond to questions about the study’s findings.

Research funding was provided by the Chinese Academy of Sciences and the National Natural Science Foundation of China.

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