Flinders University paleontologist Brian Choo and his colleagues have described a new genus and species of Devonian tetrapodomorph fish based on several nearly complete skulls and postcranial skeletons.
“Tetrapodomorpha comprises the limbed tetrapods and their closest fish relatives, whose earliest record is from the Pragian of China,” Dr. Choo and co-authors said.
“The group diversified greatly in both marine and freshwater habitats during the Middle-to-Late Devonian while giving rise to several distinct lineages, including the earliest limbed tetrapods.”
“Whereas the tetrapods flourished after the Devonian, limbless fish-grade tetrapodomorphs underwent a marked reduction in diversity during the Carboniferous, with only a handful of representatives persisting into the early Permian before vanishing from the fossil record.”
The new tetrapodomorph species lived around 380 million years ago and was up to 45-50 cm in length.
Scientifically named Harajicadectes zhumini, the fish is particularly distinctive for its large openings on the top of their skull.
“These spiracular structures are thought to facilitate surface air-breathing, with modern-day African bichir fish having similar structures for taking in air at the water’s surface,” Dr. Choo said.
“This feature appears in multiple tetrapomodorph lineages at about the same time during the Middle-Late Devonian.”
“In addition to Harajicadectes zhumini from central Australia, large spiracles also appeared in Gogonasus from Western Australia and elpistostegalians like Tiktaalik — the closest relatives to limbed tetrapods.”
“Plus it also appears in the unrelated Pickeringius a ray-finned fish from Western Australia, first described in 2018.”
“The synchronized appearance of this air-breathing adaptation may have coincided with a time of decreased atmospheric oxygen during the mid-Devonian,” said Flinders University’s Professor John Long.
“The ability to supplement gill…
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