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New gliding reptile: Mecistotrachelos

Sorry Dr. Fraser, et al. didn't consider comparing his new find to Coelurosauravus with more vigor.
Seems the hangup was the nature of the gliding membrane 'ribs'

As Fraser et al. note: Standard ribs are present in Coelurosauravus. So are bundles of rod-like neomorph ossifications.

Fraser also notes that closely related forms (Icarosaurus, Kuehneosaurus, and Kuehneosuchus) DO have exceptionally elongate thoracolumbar ribs AND markedly elongate transverse processes. (Emphasis mine)

The only problem is, (phylogenetically) elongate transverse processes are no where else to be found in ANY sister taxa near or semi-far. What that means is, the 'markedly elongate transverse processes ARE the ribs, straightened and fused to the vertebrae for (one could readily assume) strength and stability as they anchor the 'wings'. And that means the 'wings' are, as in Coelurosauravus, still supported by folding neomorphic ossifications. As a matter of fact, in Icarosaurus at the transitional dorsal vertebrae -- the ones not supporting neomorph ossifications between the scapulae -- this fusion is visible because it is incomplete. Heck, these lines are even drawn on the 1970 Colbert restoration that Fraser's group includes!!!!

Such is the power of the paradigm.

Yes, Coelurosauravus is related to Icarosaurus and Mecistotrachelos. Yes, the wings are homologous. What we see in Fraser's new gliding reptile is simply a later form that reduced and fused the ribs to the vertebrae, as in Icarosaurus, yet retained the long neck of Coelurosauravus -- and made it longer.

Coelurosauravus neck to torso ratio: 4:10  Permian
Mecistotrachelos  neck to torso ratio: 6:10  Carnian

I note that Coelurosauravus and Mecistotrachelos share many similarities not shared with Icarosaurus and kin, including
1) a pointed snout (in ventral view).
2) a lack of cervical ribs.
3) a fibula indistinguishable from the tibia
4) elongated dorsal vertebra (longer than wide or tall)

Some of the problems include:

1) not having good reconstructions of Icarosaurus, Coelurosauravus and (what's THAT doing in there??) Sharovipteryx (an Unwin tracing of a 37-year-old Sharov original drawing -- not very accurate).

2) not having a good understanding of the fossil itself (a Photoshop tracing and a reconstruction in various views should always be attempted because it opens your eyes to new possibilities, especially in low-contrast situations such as this)

3) not having a good understanding of the phylogeny of the Reptilia (Mecistotrachelos is NOT an archosauromorph, BUT a lepidosauromorph).

4) Not attempting a phylogenetic analysis.

All the above is based on the paper itself. Now taking this to the next level in Photoshop:

The non-terminal nares are visible, as in Coelurosauravus.
One curved and shield-like parietal (as in Coelurosauravus) is loose and located beneath the manus near the skull.
A pineal foramen is visible as are sclerotic rings. The view is dorso- ventral so a lateral view reconstruction would be difficult but not impossible.
Nothing that can be noted in the limbs or axis invalidates a relationship with Coelurosauravus.

So, in conclusion:

Coelurosauravus (Permian) has 23 ossified rods. The first 11 are bundled proximally and emerge from the second and third dorsal rib. The remainder, 12-23, are each associated with a rib tip

Icarosaurus (Triassic) has 13 ossified rods, all of which are associated with rib tips that look like transverse processes.

Mecistotrachelos has 9 ossified rods, all of which are associated with rib tips that look like transverse processes. The first ossified rod is very short, no longer than one dorsal vertebra. Rods 2-8, when fully deployed, appear to extend laterally, but may have not done so due to the proximal curve, which, as Fraser notes, is not present in Icarosaurus. Then again, the curve could have been in the transverse plane.

Is this a valid genus? Yes. IMHO. Based on ossified rod element numbers and cervical length principally.

David Unwin and Susan Evans provided constructive views of the manuscript.

My hat's off to the group for the discovery!

David Peters
St. Louis