Reconstruction of the life of Harajicadectes zhumini, a 40 cm long lobe-finned fish not closely related to the fishes that gave rise to the earliest limbed tetrapods. Credit: Brian Choo, Flinders University
Australia’s rivers, which once flowed through its now dry interior, were once home to a variety of strange animals – including a sleek lobe-finned predatory fish with large fangs and bony scales.
A newly described fossil fish discovered in remote fossil fields west of Alice Springs has been named Harajicadectes hum by an international team of researchers led by
The type specimen of Harajicadectes found in the field in 2016 (a nearly complete fish viewed in dorsal view), a latex shell of the fossil, and an interpretive diagram. Credit: Brian Choo, Flinders University
One of the ancient Tetrapodomorph lineage, some of which became ancestors of limbs
Flinders University paleontologist, Dr. Brian Choo, with well-preserved fossil fish (and pieces of artwork). Credit: Flinders University
The evolutionary context and impact of research
Professor Flinders John Long, a leading Australian fossil fish expert and co-author of the new discovery published in Journal of Vertebrate Paleontologysuggests that the synchronized appearance of this air-breathing adaptation may have coincided with a time of low atmospheric oxygen during the mid-Devonian.
“The ability to supplement gill respiration with aerial oxygen is likely to confer 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, almost 200 km west of Alice Springs, dating from the Middle to Late Devonian approximately 380 million. years old.
Skull of Harajicadectes in dorsal view alongside a reconstructed head, plus location of Harajica fish beds. Credit: Brian Choo (Flinders University)
“It is difficult to determine where Harajicadectes is in this group of fishes, as it appears to have convergently acquired a mosaic of specialized features characteristic of widely separated branches of the tetrapodomorph radiation.
The publication is the culmination of 50 years of exploration and research.
ANU Professor Gavin Young first discovered fragmented specimens in 1973 and many other fossils found in 1991 have been studied by the Melbourne Museum and Geosciences Australia in Canberra.
Attempts to study these fossils proved arduous until a 2016 Flinders University expedition found a nearly complete specimen.
“This fossil showed that all the isolated parts and pieces collected over the years belonged to a single new species of ancient fish,” says Dr Choo, from the Flinders College of Science and Engineering.
The 2016 specimen has been transferred to the Museum and Art Galleries of the Northern Territory in Darwin.
Reference: “A new tetrapod stalkfish from the Middle-Late Devonian of central Australia” by Brian Choo, Timothy Holland, Alice M. Clement, Benedict King, Tom Challands, Gavin Young and John A. Long, 5 Feb 2024, Journal of Vertebrate Paleontology.
This work was supported by the Australian Research Council through DECRA project DE1610024 and Discovery Grants DP0558499, DP0772138, DP160102460 and DP22100825.