Harajicadectes enters the LRT as a giant Osteolepis (Tetrapodomorpha)

Choo et al 2024 described
a new Middle to Late Devonian large (~45cm) osteolepid from Australia, Harajicadectes. The holotype is a partial skull and anterior body outline in dorsal view with heavy scales. The paratype is a partial skull, post-temporal elements and lower jaw.

The authors wrote,
“Overall, Harajicadectes presents a highly distinct mosaic of characters which elsewhere manifests in disparate tetrapodomorph taxa.”

I shudder when I read the term ‘mosaic’. That implies a patchwork of disparate elements, like Frankenstein’s monster. That’s not how evolution works.

‘Transitional’ is a better term if the taxon is a blend of predecessor and successor taxa.
‘Convergent’ is a better term if the elements are not homologs.

“Tetrapodomorpha comprises the limbed tetrapods and their closest fish relatives, whose earliest record is from the Pragian of China,” Dr. Choo and co-authors said (in publicity and in their introduction.

This member list = clade is also irksome in that only one taxon can be a ‘closest fish relative’. Otherwise, these relatives start to gradually diminish in ‘closest-ness’.

Better to indicate a last common ancestor of all tetrapodomorphs, like the first rhipidistian that is not a lungfish.

“It is notable for having greatly enlarged spiracular openings, a feature present also in Gogonasus and the elpistostegalians. This character, suggestive of spiracular air-breathing, thus appeared independently in at least three lineages of Middle–Late Devonian
tetrapodomorphs.”

That means Harajicadectes was likely a creature of the muddy or gravelly shallows, inches from dry land.

“No endoskeletal fin elements are preserved in any of the material.”

That means it did not have the internal bracing needed to pull itself onto dry land.

Lateral, dorsal and ventral fins
appear to be reduced in development. Thus propulsion was relegated to sinuous motion of the entire dorsoventrally flattened body. as in 30cm long Gyroptychius, from Northern Europe, which nested as a close relative in the authors’ cladograms.

That’s the other side of the globe from Australia. That implies worldwide distribution of clade members. Gyroptychius has not yet entered the LRT.

In a competing analysis,
the large reptile tree (LRT, 2340 taxa) Harajicadectes nests with Osteolepis. This small clade follows the Eusthenopteron to Gogonasus clade and precedes larger taxa with a flatter skull, like Barameda and Gooloogongia.

One of the authors’ two cladograms
flip those clades, moving the flatter Barameda clade closer to the base and the rounder in cross-section Eusthenopteron clade closer to flatter pre-tetrapods with smaller, internally braced fins, like Panderichthys and Tiktaalik. The other published cladogram looses resolution at those nodes. So the differences are few and subtle at this transition.

Some skull parts are relabeled here
(as elsewhere for consistency) in accord with tetrapod analogies.

Click on links above to see the data on Harajicadectes and kin.

Side note
I’m now posting on taxa that came to my attention over the past two years that were ‘put on hold’ while focusing on and working through the Mammalia.. This tetrapodomorph is one of several such postponed taxa.

References
Choo B (6 co-authors) 2024. A new stem-tetrapod fish from the Middle–Late Devonian of central Australia. Journal of Vertebrate Paleontology.
https://doi.org/10.1080/02724634.2023.2285000

wiki/Harajicadectes
wiki/Gyroptychius

Publicity

https://www.sci.news/paleontology/harajicadectes-zhumini-12661.html#google_vignette

Source: https://pterosaurheresies.wordpress.com/2026/03/17/harajicadectes-enters-the-lrt-as-a-giant-osteolepis-tetrapodomorpha/