Scientists have discovered a strange ancient fish, 380 million years old, that breathes air

Scientists have discovered a strange ancient fish, 380 million years old, that breathes air

Harajicadectes zhumini

Life reconstruction of Harajicadectes zhumini, a 40-cm-long lobed-finned fish not closely related to the fish that gave rise to the earliest limbed tetrapods. Credit: Brian Chu, Flinders University

Once flowing through the now dry interior, Australia’s rivers host a host of exotic animals – including sleek, lobe-finned predatory fish with large tusks and bony scales.

A newly described fossil fish discovered in remote fossil fields west of Alice Springs has been named Harajicadectes zhumini By an international team of researchers led by Flinders University Paleontologist Dr. Brian Chu.

The fossil is named after the Harajica Sandstone Member where fossils were found in the “red centre” of Australia and in ancient Greek dēktēs (“biting”). He also pays tribute to Professor Min Zhou, currently at the Chinese Academy of Sciences in Beijing, who made some major contributions to early 20th century research. Vertebrates.

Specimen of Harajicadectes

Harajicadectes species specimen as found in the field in 2016 (almost complete fish shown in dorsal view), latex shell from the fossil, and interpretive diagram. Credit: Brian Chu, Flinders University

One of the ancient lineages of tetrapods, some of which became ancestors of limbs Tetrapods -And after them humans- Harajicadectes It is particularly distinguished by its large openings at the top of its skull.

“These spiral structures are thought to facilitate the breathing of surface air, as modern African basilisks have similar structures for breathing air at the surface of the water,” says Dr. Brian Chu, a researcher at the Flinders Laboratory of Paleontology, who has studied the most complete specimen of this species. newly described Harajicadectes Which has grown to about 40 cm.

“This feature appears in multiple lineages of Muddorf tetrads at approximately the same time during the Late Middle Devonian.

“In addition to Harajicadectes From central Australia, large vents also appeared Jojonasus From Western Australia and Elpistostegalians such as Tiktaalik (closest relatives of tetrapods). Plus he also appears in Unrelated Pickeringius A ray-finned fish from Western Australia, first described in 2018.

Brian Chu

Flinders University paleontologist Dr Brian Chu, with well-preserved fossil fish (and interior artwork). Credit: Flinders University

Evolutionary context and impact of research

Flinders Professor John Long, Australia’s leading expert on fossil fish and co-author of the new discovery published in the journal Journal of Vertebrate PaleontologyThe simultaneous appearance of this adaptation to air breathing may have coincided with a time of low atmospheric oxygen during the middle Devonian, he says.

“The ability to supplement gill respiration with atmospheric oxygen likely provided an adaptive advantage,” says Professor Long.

“We found this new form of lobe-finned fish in one of the most remote fossil sites in all of Australia, the Harajica Sandstone Member in the Northern Territory, about 200 kilometers west of Alice Springs, dating to the Late Middle Devonian of ca. 380 million years. Years.

Harajicadectes skull

Harajicadectes skull in dorsal view next to a reconstructed head, as well as the location of the Harajica Aquariums. Credit: Brian Chu (Flinders University)

“It’s hard to say where Harajicadectes It falls into this group of fishes where it appears to have convergently acquired a mosaic of specialized features characteristic of widely separated branches of the tetrapod radiation.

This publication is the culmination of fifty years of exploration and research.

Australian National University professor Gavin Young first discovered fragmentary specimens in 1973, and several fossils recovered in 1991 were studied by the Melbourne Museum and the Australian Geosciences Foundation in Canberra.

Attempts to study these fossils proved troublesome until a 2016 Flinders University expedition found an almost complete specimen.

“This fossil showed that all the isolated bits and pieces collected over the years belonged to a single new species of ancient fish,” says Dr Chu, from Flinders College of Science and Engineering.

The 2016 specimen was transported to the Northern Territory Museum and Art Galleries in Darwin.

Reference: “New tetrapod fishes from the Middle and Late Devonian of central Australia” by Brian Chow, Timothy Holland, and Alice M. Clement, Benedict King, Tom Challands, Gavin Young, and John A. Long, February 5, 2024, Journal of Vertebrate Paleontology.
doi: 10.1080/02724634.2023.2285000

This work was supported by the Australian Research Council through DECRA project DE1610024, and Discovery Grants DP0558499, DP0772138, DP160102460, and DP22100825.

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