Fossil remains have provided fascinating insights into diverse ancient fish species that once lived on this planet – ranging from heavily armored specimens to those with distinctive lobe fins.
The study of these ancient fish species through fossils has significantly contributed to our understanding of the evolution of vertebrates and the development of various adaptations for life in aquatic environments.
Now it’s time to introduce a new type of ancient lobe-finned fish — a sleek creature with big fangs and bony scales. The fish fossils are from the Middle-Late Devonian era, which occurred roughly 380 million years ago.
This predatory marine creature once thrived in what is now Australia when rivers flowed over the now-dry landscape.
Paleontologists at Flinders University have named the newly discovered fish species Harajicadectes zhumini.
The fossilized remains were discovered at the Harajica Sandstone Member, a remote fossil site in Australia's Northern Territory, almost 200 kilometers west of Alice Springs.
Fossils showcase the presence of spiracular structures
Based on the fossilized bones, the scientists predict that individuals of this species grew to be around 40 cm in size as adults.
Belonging to the ancient Tetrapodomorph lineage, the recently identified species exhibits unique biological features.
Examination of the specimen revealed the presence of large holes in the upper region 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,” said Brian Choo, who led the fossil examination.
“This feature appears in multiple Tetrapomodorph lineages at about the same time during the Middle-Late Devonian,” added Choo.
The authors highlight that the notable biological feature of a large spiracle has been observed in a variety of other ancient lobe-finned fish species, including Gogonasus from Western Australia.
Another example of this trait is found in Pickeringius, an unrelated ray-finned fish species from Western Australia, which was first discovered in 2018.
This feature evolved to adapt to low oxygen levels
The origin of this adaption for air-breathing may have coincided with a time of low atmospheric oxygen levels in the mid-Devonian.
“The ability to supplement gill respiration with aerial oxygen likely afforded an adaptive advantage,” said John Long, a leading Australian expert on fossil fish and coauthor of this new study.
“It is difficult to pinpoint where Harajicadectes sits in this group of fish as it appears to have convergently acquired a mosaic of specialized features characteristic of widely separate branches of the tetrapodomorph radiation,” Long concluded in the press release.
The findings were reported in the Journal of Vertebrate Paleontology.
