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Description
2021+2023. Acrylics, digital & photography.

ca. 385-380,000,000 bp. Middle-Late Devonian (Givetian-Frasnian), Northern Territory, Australia (Harajica Sandstone Member)

In an ancient freshwater river that weaves through what will become central Australia, a Harajicadectes inspects a pair of juvenile Bothriolepis who hope their armor-plating is a sufficient deterrence against attack.

Harajicadectes zhumini (Prof. Min Zhu's Harajica-biter) is a tetrapodomorph fish that my colleagues and I described in February 2024. It's fossils are from an incredibly remote Middle-Late Devonian outcrop over 160 km to the west of Alice Springs, within the Amadeus Basin of Central Australia. The red sandstones record a mass death of hundreds of small Bothriolepis along with rarer phyllolepids, acanthodians, dipnoans (Harajicadipterus), plus our new tetrapodomorph. Known from an almost body fossil and at least 16 less complete specimens, this is the earliest Central Australian bony fish known from reasonably complete remains. At up to 40 cm in length, it was the largest fish in the assemblage and likely the apex predator of it's habitat.

The most distinctive feature of Harajicadectes are the huge paired spiracular openings on the skull roof. Modern bichirs use similar structures to breathe air at surface, aiding their survival in stagnant waters. Intriguingly, this adaptation arose in at least 3 lineages of Devonian tetrapodomorphs = the elpistostegalians (Tiktaalik & friends), Gogonasus (a reef-dweller from Western Australia), and now Harajicadectes. The actinopterygian Pickeringius (a contemporary of Gogonasus) also had them. The roughly simultaneous appearance of surface-breathing adaptations in 4 osteichthyan groups during in the latter part of the Devonian is a point of interest for ongoing research into modelling Palaeozoic oxygen levels.

Our description of Harajicadectes is the culmination of 50 years of exploration and research. Gavin Young from the Australian National University in Canberra made the initial discoveries in 1973. More partial specimens were collected in 1991, but attempts to describe the fossils fell flat until the 2016 Flinders University Expedition unearthed the almost complete fish which now serves as the holotype.

REFERENCE
Choo, Brian; Holland, Timothy; Clement, Alice M.; King, Benedict; Challands, Tom; Young, Gavin; Long, John A. (2024). "A new stem-tetrapod fish from the Middle–Late Devonian of central Australia" . Journal of Vertebrate Paleontology. doi :10.1080/02724634.2023.2285000 .

Article in The Conversation = theconversation.com/a-380-mill…

Description
2021+2023. Acrylics, digital & photography.

ca. 385-380,000,000 bp. Middle-Late Devonian (Givetian-Frasnian), Northern Territory, Australia (Harajica Sandstone Member)

In an ancient freshwater river that weaves through what will become central Australia, a Harajicadectes inspects a pair of juvenile Bothriolepis who hope their armor-plating is a sufficient deterrence against attack.

Harajicadectes zhumini (Prof. Min Zhu's Harajica-biter) is a tetrapodomorph fish that my colleagues and I described in February 2024. It's fossils are from an incredibly remote Middle-Late Devonian outcrop over 160 km to the west of Alice Springs, within the Amadeus Basin of Central Australia. The red sandstones record a mass death of hundreds of small Bothriolepis along with rarer phyllolepids, acanthodians, dipnoans (Harajicadipterus), plus our new tetrapodomorph. Known from an almost body fossil and at least 16 less complete specimens, this is the earliest Central Australian bony fish known from reasonably complete remains. At up to 40 cm in length, it was the largest fish in the assemblage and likely the apex predator of it's habitat.

The most distinctive feature of Harajicadectes are the huge paired spiracular openings on the skull roof. Modern bichirs use similar structures to breathe air at surface, aiding their survival in stagnant waters. Intriguingly, this adaptation arose in at least 3 lineages of Devonian tetrapodomorphs = the elpistostegalians (Tiktaalik & friends), Gogonasus (a reef-dweller from Western Australia), and now Harajicadectes. The actinopterygian Pickeringius (a contemporary of Gogonasus) also had them. The roughly simultaneous appearance of surface-breathing adaptations in 4 osteichthyan groups during in the latter part of the Devonian is a point of interest for ongoing research into modelling Palaeozoic oxygen levels.

Our description of Harajicadectes is the culmination of 50 years of exploration and research. Gavin Young from the Australian National University in Canberra made the initial discoveries in 1973. More partial specimens were collected in 1991, but attempts to describe the fossils fell flat until the 2016 Flinders University Expedition unearthed the almost complete fish which now serves as the holotype.

REFERENCE
Choo, Brian; Holland, Timothy; Clement, Alice M.; King, Benedict; Challands, Tom; Young, Gavin; Long, John A. (2024). "A new stem-tetrapod fish from the Middle–Late Devonian of central Australia" . Journal of Vertebrate Paleontology. doi :10.1080/02724634.2023.2285000 .

Article in The Conversation = theconversation.com/a-380-mill…