A new fossilized galeaspid species, Foxaspis novemura, has been discovered in China, featuring a unique nine-rayed caudal fin. The species was found to be an active swimmer with a faster cruising speed than its relatives.
Researchers have discovered a new fossilized galeaspid species with “nine tails” in south China’s Guangxi Zhuang Autonomous Region. This is the world’s first galeaspid fossil with a well-preserved tail.
According to the researchers from the Institute of Vertebrate Paleontology and Paleoanthropology under the Chinese Academy of Sciences, they named the new species as Foxaspis novemura because its caudal fin is comprised of nine ray-like scale-covered digitations, just like that of the Nine-Tailed Fox, a mythical animal from an ancient literature “Shan Hai Jing” (Classic of Mountains and Seas).
The fossil specimen completely preserves the caudal fin in both folded and flared states, revealing its morphological details to the greatest extent, according to Gai Zhikun, a research professor from the institute.
“We discovered that galeaspids may be active swimmers, and can make good use of muscle contraction to control the contact area between tail and water flow, thus generating different thrust forces,” he said.
The team then analyzed the swimming speed of the geometrical morphology of the tail and showed that galeaspid’s cruising speed was even faster than that of their more derived jawless and jawed relatives.
The researchers published their study results in the journal National Science Review.
Reference: “Postcranial disparity of galeaspids and the evolution of swimming speeds in stem-gnathostomes” by Zhikun Gai, Xianghong Lin, Xianren Shan, Humberto G Ferrón and Philip C J Donoghue, 27 February 2023, National Science Review.
DOI: 10.1093/nsr/nwad050
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