A new species – and genus – of armored jawless fish has come to light in the Chinese rocks dating to the Pragian stage of Devonian.

The fish, named Rhegmaspis xiphoidea, belongs to an extinct group of jawless marine and freshwater fish called galeaspids, characterized by their big and bizarre head-shields.

The species swam in Devonian period seas about 410 million years ago, long before dinosaurs lived on Earth, according to a study published in the journal Vertebrata PalAsiatica.

It had a torpedo-shaped head-shield with a ‘breathing hole’ on top and a sword-like nose.

The complete fish would have been 2 to 2.8 inches (5-7 cm) long when it was alive.

Dr Zhi-Kun Gai of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and co-authors made the discovery in rocks on the Posongchong Formation in Yunnan Province, China.

The fossil specimens of Rhegmaspis xiphoidea that the paleontologists used to characterize this new genus and species come from multiple individuals and include complete head-shields and one incomplete endocast of a skull.

“As a streamlined jawless fish, Rhegmaspis xiphoidea displays an adaptation for a suprabenthic lifestyle with more active feeding behavior among galeaspids,” Dr Gai said.

“The new form not only enriches the diversity of the Huananaspiformes, but also provides evidence for the last adaptive radiation of galeaspids by occupying an unexploited ecological niche during the Pragian of the Early Devonian.”

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Zhi-Kun Gai et al. 2015. A streamlined jawless fish (Galeaspida) from the Lower Devonian of Yunnan, China and its taxonomic and paleoecological implications. Vertebrata PalAsiatica, vol. 53, no. 2, pp. 93-109