More than 380 million years ago, smooth, air-breathing predatory fish patrolled the rivers of central Australia. Today, those river deposits form red sandstone outcrops in remote hinterlands.
Our new paper Journal of Vertebrate Paleontologydescribes the fossil of this fish we named. Harajikadectes zumini.
Known from at least 17 fossil specimens, Harajika Dectes It is the first partially complete teleost fish discovered in Devonian rocks of central Australia. It has also been proven to be one of the rarest animals.
meet someone who bites
The name refers to the location where the fossil was discovered, its presumed predatory habits, and means “Ming Zhu’s Harajuku-biter” in honor of a prominent Chinese paleontologist. Min Joomade many contributions to early vertebrate research.
Harajika Dectes It was a fish inside Tetrapodomorpha group. This group had a pair of well-built fins and usually only had a pair of external nostrils.
Tetrapodomorph fishes from the Devonian Period (359 to 419 million years ago) have long been of great interest to science. These include the forerunners of modern tetrapods, animals with backbones and limbs such as amphibians, reptiles, birds, and mammals.
For example, recent fossil discoveries show that fingers and toes arose. in this group.
Read more: When fish gave us fingers: This ancient quadruped fish reveals the origin of human hands
Devonian fossil remains northwest and eastern Australia has produced many amazing discoveries of early tetrapods.
However, until our discovery, the continent’s interior had been poorly explored, and only interesting fossil fragments had been discovered.
The long road to discovery
Our species description is the culmination of 50 years of tireless exploration and research.
Australian National University palaeontologist Gavin Young made the first discovery in 1973 while exploring the mid-late Devonian Haladika sandstone in the Luricha/Arrernte country, more than 150 kilometers west of Alice Springs (Mpartwe).
The remains of hundreds of fish were packed into blocks of red sandstone on a secluded hill.most of them were small botryolepis – A type of widespread prehistoric fish known as. plate coatingcovered in box-like armor.
Pieces of other fish were scattered inside.These include: lungfish also known as Harajikadipterus yonginamed in honor of Gavin Young and his years of research into Harajika material.
Also found are spines from ecanthophores (small, vaguely shark-like fish), lamina from foliar fishes (very flat plate skins), and, most interestingly, fragments of previously unknown tetrapod jaws. There was also.
Author provided
More partial specimens of this moose tetrapod were collected in 1991, including one by the late paleontologist. alex richie.
There were early attempts to identify the species, but this proved difficult. Then, in 2016, Flinders University visited the site and discovered the first near-complete fossil of the animal.
This beautiful specimen proved that all the isolated fragments collected over the years belonged to a single new type of fish. It is now held in the collections of Northern Territory museums and galleries. type specimen of Harajika Dectes.
Author provided
strange apex predator
Maximum body length is 40 cm, Harajika Dectes It is the largest fish found in Harajika Rock. Perhaps the apex predator of these ancient rivers, its large mouth was lined with dense, sharp teeth alongside larger, more widely spaced triangular fangs.
It is thought that the anatomical features of different tetrapod lineages were combined through convergent evolution (in which different organisms independently evolve similar features). Examples include the bone patterns of the skull and scales. It is difficult to work out where exactly it ranks among its closest relatives.
Artist: Brian Chu
The most striking and perhaps most important features are the two huge openings at the top of the skull called the spiracles. These usually appear only as minute slits in most early teleosts.
Similar giant spiracles gogonathus, a marine quadruped that inhabits the famous Late Devonian Gogo Formation of Western Australia. (They don’t seem to be direct relatives) Harajika Dectes. )
Can be seen even in unrelated places Pickeringiusan early stingray fish that was also found in Gogo.
The oldest air breathing apparatus?
Other Devonian animals that flaunted such spiracles include the famous Elpistostegalian, a freshwater tetrapod of the northern hemisphere. elpisto stage and Tiktaalik.
These animals were very close to the ancestors of limbed vertebrates. Thus, enlarged spiracles appear to have arisen independently in at least four separate lineages of Devonian fish.
Author provided
The only modern fish with a similar structure is the bichir, an African stingray fish that lives in shallow floodplains and estuaries. Recently, it was observed that they take in surface air through their spiracles to help them survive in oxygen-poor waters.
The nearly simultaneous appearance of these structures in the four Devonian lineages provides a fossil “signal” to scientists trying to reconstruct atmospheric conditions in the distant past.
This could help elucidate the evolution of air breathing in vertebrates.
