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Reenactment of the life of Harajicadectes zhumini, a 40 cm long lobe-finned fish. This fish is not far from the fish that gave rise to the earliest four-legged quadrupeds.Credit: Brian Choo, Flinders University
Australia’s rivers once flowed through what is now an arid interior and were home to a variety of strange animals, including smooth, predatory lobe-finned fish with large tusks and bony scales. Was.
A newly described fish fossil discovered in a remote fossil field west of Alice Springs has been named. Harajikadectes zumini By an international team of researchers led by flinders university Paleontologist Dr. Brian Chu.
The fossil is named after the Harajika Sandstone Formation, where the fossil was discovered in Australia’s “Red Center”, and after the ancient Greek dēktēs (meaning “chewer”). We also pay tribute to Professor Ming Zhu, currently at the Chinese Academy of Sciences in Beijing, who made significant contributions to early scientific research. vertebrate.
A schematic specimen of Harajikadectes (an almost complete fish seen from the back), fossilized latex skin, and explanatory drawings discovered in the field in 2016.Credit: Brian Choo, Flinders University
a lineage of ancient tetrapodomorphs, some of which were ancestors of tetrapods tetrapod – And then humanity – Harajika Dectes The large opening at the top of the skull is particularly distinctive.
“These spire-like structures are thought to facilitate air breathing at the surface, and modern African bichir fish have similar structures for taking in air at the surface.” Dr Brian Chew, a researcher at the Flinders Institute of Paleontology who studied the most complete specimen, said:newly written Harajika Dectes It has grown to about 40cm.
“This feature appears in multiple tetrapomodorf lineages at about the same time during the middle to late Devonian.
“In addition to Harajika Dectes Large spiracles also appeared from central Australia. gogonathus El Pisto Stegarian from Western Australia Tiktaalik (closest relative of four-limbed quadrupeds).It also appears in unrelated places. Pickeringius Western Australian stingray fin fish first described in 2018. ”
Flinders University paleontologist Dr Brian Chew with a well-preserved fish fossil (and inserted artwork).Credit: Flinders University
Evolutionary background and impact on research
Flinders Professor John Long is Australia’s leading fish fossil expert and co-author of this new discovery. Journal of Vertebrate Paleontologystate that this synchronous emergence of air-breathing adaptations may have coincided with a period of reduced atmospheric oxygen during the Middle Devonian.
“The ability to supplement gill breathing with oxygen from the air likely provided an adaptive advantage,” Professor Long said.
“We discovered this new form of lobe-finned fish in one of the most remote fossil sites in all of Australia, the Harajika Sandstone Formation in the Northern Territory, about 200km west of Alice Springs. It dates back to 80 million years ago, during the middle to late Devonian period.
Rear view of the skull of Harajikadectes. Along with the reconstructed head, the location of the moose’s fish bed is also shown. Credit: Brian Choo (Flinders University)
“It’s difficult to pinpoint the location. Harajika Dectes sit in this group of fishes because they appear to have convergently acquired a mosaic of specialized features characteristic of broadly separate branches of the tetrapod radiation. ”
This publication is the culmination of 50 years of exploration and research.
Professor Gavin Young from ANU discovered the first fragmentary specimen in 1973, and further fossils recovered in 1991 were studied by Melbourne Museum and Geoscience Australia in Canberra.
Attempts to study these fossils proved difficult until a 2016 expedition from Flinders University discovered a nearly complete specimen.
“This fossil proves that all the isolated fragments collected over the years belong to a single new type of ancient fish,” says Dr Chu, from the Flinders School of Science and Engineering.
The 2016 specimen was transferred to the Northern Territory Museum and Art Gallery in Darwin.
References: ‘A new mid-late Devonian stem tetrapod of central Australia’, Brian Chew, Timothy Holland, Alice M. Clement, Benedict King, Tom Challans, Gavin Young, John A. By Long, February 5, 2024, Journal of Vertebrate Paleontology.
DOI: 10.1080/02724634.2023.2285000
This research was supported by the Australian Research Council through DECRA project DE1610024 and Discovery Grants DP0558499, DP0772138, DP160102460 and DP22100825.
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