O’Callagan-Linford 2024 reviews the origin of birds

The following is a critique of a ResearchGate.net preprint.
All papers invite comment. So do published preprints. I hope the following will be helpful.

From the abstract
“Despite specious criticism, the connected phylogeny between non-avian dinosaurs and avians has been well-documented since 1868 with Thomas Henry Huxley’s description of the “urvogel” Archaeopteryx lithographica holotype from the Solnhofen Limestone,”

Ahh, hindsight. The young author seems to be not aware of the struggle of this hypothesis for the first 130 years. Not sure why this subject is the subject of another paper (preprint) when the connection has been “well-documented.” Usually in abstracts the author sets up a problem then tells readers how they are going to resolve the problem with discovery or insight.

By the way,  there are 13 ‘urvogels’ = Solnhfen birds. None are identical to one another. Many nest in various basal bird clades in the LRT. If you know this student, tell him to study all 13, if possible, and write a paper on the phylogeny of all 13. Don’t lump all Solnhofen birds into one taxon, like other bird and theropod workers do.

O’Callagan-Linford continues:
“At the most basic level, locomotive evolution into the third dimension by lifting the stomach off of the ground and walking propped-up is a privilege enjoyed by only two vertebrate groups—the diapsid archosaurs, including dinosaurs, avians and crocodylomorphs, and the synapsids, which gave rise to the mammals.

Chlamydosaurus, the Austrlian frill-neck lizard ” data-image-caption=”

Fig. 4 Chlamydosaurus, the Austrlian frill-neck lizard with an erect spine and elevated tail.

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Fig. 1.  Chlamydosaurus, the Austrlian frill-neck lizard with an erect spine and elevated tail.

Add at least two lizards to this list, Chlamydosaurus (Fig 1) and Basiliscus. Pterosaurs and kin, like Sharovipteryx (Fig 2), also lifted the stomach off the ground.

“Unique to avians, postcranial pneumaticity is thought to be an adaptation to aid in the
intake of oxygen during flight (Costain & Hack, 2018) and represents an extension to
the respiratory system.”

Other dinosaurs and, by convergence, pterosaurs and kin, too.

The author mentions
“three-fingered grasping hands” on Deinonychus. I realize this hypothesis is often found in the literature.

Are we sure about this? Living birds with wing claws never grasp prey or anything else. Perhaps these were never grasping organs. Perhaps the pectoral limbs of theropdos were ideal for slashing. Or never-to-rarely used. Is there a citation for ‘grasping’, or is this a recurrent theme, the product of imagination, a trope, or a myth with no merit?

To that point, pterosaurs also have sharp claws on their forelimbs. They are reduced on beach-walkers like Pterodaustro, that walked on all fours. Some workers think pterosaurs with large hand claws, like Dimorphodon, also walked on their hands. Nobody has ever suggested they were used in grasping prey = another paper for this young author.

Note: the word ‘coracoid’ never appears in this text.
Here (Fig 2) an elongate, locked-down coracoid signals flapping in non-volant pterosaur ancestor and bird-like theropods. Too bad this key trait was missed.

Figure 2. Sharovipteryx flapping while running. Note the elongate coracoids meeting the strap-like scapulae, as in birds and pteroaurs.

The author also buys into and promotes
the membrane-winged hypothesis of Ambopteryx and Yi qi (Fig 3). Maybe this author has to do this to graduate from the U of Portsmouth, where he studies. Unfortunately ‘flapping’ is only mentioned twice in the text, once in the abstract and again with regard to these two bird taxa. Flapping is not linked to the origin of birds in this paper with a headline that includes the term, “flight locomotion.”

Figure x. Reconstruction of Yi qi with a typical tetrapod – bird reconstruction. ” data-image-caption=”

Figure x. Reconstruction of Yi qi with a typical tetrapod – bird reconstruction.

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Figure x. Reconstruction of Yi qi with a typical tetrapod – bird reconstruction.

From the conclusion
“Today, there is little doubt over the dinosaurian origin and identification of the Neornithes; maniraptorans. The heightened discovery rate since the 1960s of well-preserved bird-like theropods has not only secured this hypothesis despite specious criticism, but has also greatly improved our understanding of modern ornithology, and how avian osteological morphology has developed.”

This student has learned his lessons well. This paper is par for the course. But this paper should have been  a chapter in a book from 1990, not a 2024 paper.
Kinda wish young Ethan would have shed some new light on this subject.
Suggestions provided above.

References
O’Callagan-Linford E 2024. Comparative osteology of dinosaurs and avians, flight locomotion, and the origin of Neornithes. Preprint DOI: 10.13140/RG.2.2.11215.70568

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