Wadisuchus, new dyrosaurid from Cretaceous of Egypt

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

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Wadisuchus kassabi gen. et sp. nov.

Sara Saber, Belal S Salem, Khaled Ouda, Abdullah S Gohar, Sanaa El-Sayed, Patrick M O’Connor, Hesham M Sallam (2025)
An early dyrosaurid (Wadisuchus kassabi gen. et sp. nov.) from the Campanian of Egypt sheds light on the origin and biogeography of Dyrosauridae
Zoological Journal of the Linnean Society 205(2): zlaf134
doi: https://doi.org/10.1093/zoolinnean/zlaf134
https://academic.oup.com/zoolinnean/article-abstract/205/2/zlaf134/8301323


Dyrosauridae are a clade of crocodyliforms characterized by diverse cranial morphologies and a broad palaeogeographic distribution from the Late Cretaceous to the Palaeogene. However, their early evolutionary history remains poorly understood due to a significant fossil gap during the Campanian. Here, we describe Wadisuchus kassabi gen. et sp. nov., an early-diverging dyrosaurid from the middle Campanian Quseir Formation of Egypt, based on two partial skulls and three partial mandibles. This new taxon displays transitional cranial features—including reduced premaxillary alveoli, modified occlusion patterns, and dorsally positioned external nares—that clarify aspects of cranial evolution related to longirostry in early dyrosaurids. Phylogenetic analyses consistently recover Wadisuchus as the earliest-diverging dyrosaurid, closely related to Chenanisuchus and distinct from Elosuchus, supporting a transition from dyrosauroids to dyrosaurids. Its Campanian age extends the temporal range of the clade and suggests that transatlantic dispersal from Africa to South America occurred earlier than previously recognized. Alongside Brachiosuchus kababishensis from Sudan, the new Egyptian taxon also implies that reverse dispersal into Africa preceded the Maastrichtian. Wadisuchus provides critical insights into the early diversification, palaeobiogeography, and cranial evolution of Dyrosauridae, confirming longirostry as an early-acquired trait and highlighting North Africa as a key region in their origin.

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[Gregory Paul]

I cannot believe it. It is like a Twilight Zone episode where the past comes alive again. I am seeing in news coverage the old saw offered by researchers that if the small TT-zone tyrannosaurs are not juvie Tyrannosaurus, then where are all the wee little cute Tyrannos? 

Read the literature people. Peter L has been pointing out such specimens for years. Nick L and Evans S did so in 2024. I have gobs of them in https://doi.org/10.11646/mesozoic.2.2.1 (8500 views so far and no news coverage). Check out its Fig. 8. Here is a list of them from the paper -- USNM6183, UCRCV1, LACM23845 (Dinotyrannus megagracilis holotype), BHI6439, KU156375, UCMP84133, and Baby Bob (Fig. 8B–D; Lipkin et al., 2007; Schmerge & Rothschild, 2016a, b; Burnham et al., 2018; Paul et al., 2022; Longrich & Saitta, 2024). They are adorable little Tyrannosauruses with the same tooth count, more robust teeth, lack of a prominent dentary groove, shorter tibia and so on. Similar to similar sized tarbosaurs which as the Raun et al. (I think it is) SVP abstract note are the best model for Tyrannosaurus ontogeny. 

None of these babies is close to complete, and the baso-eutyrannosaurs which are not all Nanos are twice as numerous. Why? Cause the latter having evolved over in Appalachia as small tyrannosaur specialists were heading over the new Laralachia land bridge (my name from the Mesozoic paper, it there is a prior names let me know) giving the poor Tyranno juvenile clunkers trying to grow into massive grownups and with those pathetic arms a very hard time, the dear things. 

Did anyone actually read the Mesozoic paper? 

Why are people still clinging to the ETRH? It never made sense with teeth being lost with onteogeny and fish like metamorphosis never seen in amniotes. Gilmore got it right 80 years ago with solid comparative anatomy. He could count teeth. 

A drop the are no clear cut Tyrannosaurus juvenile fossils. 

GSPaul

[Franco Sancarlo]

I was thinking the same thing, it's paradossal that people are ignoring your paper and Longrich et Saitta (2024)

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[Thomas Carr]

Speaking for myself, the question ("where are all the true juvenile rexes?") was asked in the context of given their hypothesis specifically, which specimens are true juvenile rexes; that is, in their specific framework? In other words, are they in alignment with the previous hypotheses of true juvenile rexes of other workers, such as yours.

-t.

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[Tim Williams]

Gregory Paul wrote:

> poor Tyranno juvenile clunkers trying to grow into massive grownups and with those pathetic arms a very hard time, the dear things.

I doubt those puny arms made any difference to their survival.  The arms of most theropods - adults and juveniles alike - look pretty useless for predation.  Depending on the lineage, theropod arms could have been used for display, intraspecific combat, carrying food, digging, flight, etc.  But as a general rule for predatory theropods, the prey catching abilities of the arms are highly overrated. _Nanotyrannus_ is no exception.  The arms are still *very* short.

For tyrannosaurines, evolution ultimately decided to drastically shrink the arms and get them out of the way.  (Of course, they weren't the first lineage to do that.)

[Heinrich Mallison]

Tim,

survival /= predation! There's way more to it than just getting at food.

Also, if those arms were without function, one would expect them to degenerate. What we see is a fully functional limb with well defined articulations and a noticeable robustness - compare to a roughly equally long human arm! And we do see vestigial arms in other large thereopods, e.g. Carnotaurus. Why not in tyrannosaurs? They did *something* important with their arms, something that required a fully functional set of joints. Just what? We apparently do not know. But it wasn't "nothing". 

Personally, I always point out that they may have had fully feathered arms, with highly visible long feathers on them, which were hidden with the arms folded (camouflage for hunting) but well visible with the arms extended (for courtship). That's a WAG (wild ass guess), but is fits the osteology MUCH better than saying "they did nothing". 

_______________________________________________________
Dr. Heinrich Mallison

cell: +49 (0)179 5429922
email: heinrich...@gmail.com
blog: dinosaurpalaeo.wordpress.com

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[Gregory Paul]

Agreed. What now needs to be done is functional work on the BM forelimbs (would be nice to also do the even larger Jodi hands see Fig. 9 in my Mesozoic paper, and those of Drypto which are more robust). I don't know how much the arms could be folded, particularly at the wrist.

GSPaul

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[Mike Habib]

Tim didn’t say the forelimbs were useless - he listed several potential functions, in fact. But his core point regarding survival impact seems robust. The most notable feature of the tyrannosaur  forelimbs is their reduction. Are they more robust than in some taxa? Sure. But compared to the ancestral state they are reduced in essentially every way.

What we actually expect to see in limited function limb reduction is a lot of variability - some will be stout, some will be lanky, some will reduced digit count, some will reduce digit size. Range of motion can be all over the place. This is precisely what is seen in secondarily flightless birds (with the caveat that the super stout reduced forelimb variant seen in things like abelisaurs seems not to show up). There’s no rule on how the developmental patterns of reduction must play out. Since the reductions are independent, we should fully expect them to play out differently across the various lineages.

While I do agree with Greg that a mechanical analysis would be interesting, I do find it a bit bizarre that there has been so much interest in the functional parameters of taxa with *reduced* limbs instead of those with more typical limb morphologies. We don’t really understand forelimb use in the non-reduced state among theropods, except for flyers. Presumably the behaviors utilized by species with reduced limbs was just a subset of the ancestral state. So step one is the ancestral state.

Cheers,

—Mike

On Oct 31, 2025, at 12:32 PM, Heinrich Mallison <heinrich...@gmail.com> wrote:



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[Jaime Headden]

In fact, we've gone over this exact topic before, the last time "vestigialization" was brought up!

Cheers,

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Jaime A. Headden

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"Innocent, unbiased observation is a myth" - P. B. Medawar (1969)

[Jura]

I completely agree with Mike here and echo his sentiments. There has been way too much interest in the arms of Abelisaurs, Tyrannosaurs, and Alverezsaurs. Meanwhile, Carnosaurs, Ceratosaurs, and Coelophysids remain completely unstudied. We should be figuring out what theropods were doing with their well-developed arms before we even broach the topic of what reduced-armed theropods were doing.

— Jason

[Jaime Headden]

One of the more interesting phenomena is that you'd think at some point that inventive artists would devise things to *do* with forelimbs that just hang there, dangling in the wind, while dancing around and being extra careful with their hindlimbs and toe positioning and all that. Most art tends to show chicken lower-leg ranges (thanks in part to the Gatesy et al studies) and less crocodilian style motion (which is changing, slowly, as uptake occurs thanks to the Hutchinson et al studies) or even abnormal squatting postures and motion.

Experimentation requires someone to "imagine" the animal doing a thing, then seeing if it was permissible or inhibited, with various studies (Tsuihiji, Hutchinson, Senter and others) focusing on either or both. Many of those requires observations and actual analysis.

One major problem, as Jura and Mike are referring to above, is that theropod forelimbs are, mostly, unique. There are bipedal mammals that use their well-developed forelimbs for things other than locomotion (kangaroos were brought up in previous threads, but there's also jerboas, and then there's conventional quadrupeds that have high mobility manipulative functions of the forelimbs (many of which are climbers, possibly adapting their limbs from that to manipulations, such as primates, koalas, raccoons, many mustelid-grade caniforms, even some cats and fossa, to say nothing of muroid rodents)) and those are hardly studied even in their own fields!

It took us relatively recently to even get to the point where we could say whether or not elephants can *run*, and penguins mechanically do fly.

I bring up art because for the most part, we kinda need to start a bit with imagination. A good reference point, if we really need to bring bird-style theropods into this question, is to follow digit reduction trends and forelimb use in oviraptorids, which range from "conventional maniraptoran long forelimbs with slender and subequal II-III [homologue III-IV]" to "reduced, stout, outer digit reduction, and big giant thumbs." It's always the thumbs! Why the thumbs? What constraints enforce thumbs over other digits that occurs in a host of taxa? If the frameshift and reduction is always outwards to inwards, that makes sense, but the thumbs just keep getting bigger.

Anyways, Cheers,

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[Gregory Paul]

Another issue is that if you have one set of researchers do one forelimb type over here and another bunch a different form over there then differing methods can reduce the comparability of the results. Would be good to have a broad array of arms examined by one team from basal theropods to birds. 

This is similar to how my skeletals are produced and posed to consistent standards to maximize comparability. 

GSPaul

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[Tim Williams]

Yes, as Mike mentioned, I never said that the forelimbs of predatory theropods were useless.  I'm casting doubt on the assumption that predatory theropods used their forelimbs for catching and handling prey.

One specimen that is instructive in this regard is the _Dilophosaurus_ specimen UCMP 37302 with severely damaged and deformed forelimbs (Senter & Juengst, 2016).  The fractures healed and the _Dilophosaurus_ survived, despite the forelimbs being severely compromised.  But damaged forelimbs may have impacted other aspects of _Dilophosaurus_ life - such as breeding, if the forelimbs were used for display or intraspecific combat.

For tyrannosaurids, Zanno & Napoli note that both _Nanotyrannus_ and _Dryptosaurus_ have relatively large hands.  This theme was taken up by some news articles, in suggesting that the enlarged hands and claws of _Nanotyrannus_ would have been used for prey capture - in contrast to _Tyrannosaurus_.  I'm highly skeptical of this interpretation.  

[Thomas Yazbek]

Complete baseless amateur speculation here, but perhaps the fact that avian wings evolved from t-pod forelimbs indicates that they were *not* serving any function essential enough to resist selection for flight? There is of course the idea that the flight stroke is derived from forelimb movement for prey apprehension. But I don't know whether it's still considered a serious hypothesis.

T. Yazbeck

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[Jaime Headden]

There have been some hypotheses put forward that indicate habitual and even locomotive pressures put on theropod forelimbs that were then exapted for flight, or rather WAIR (at the time), which then became an adaptive playground leading to flight. Flight, like birdiness, unlike how some might aver, was not the goal and thus selective product of this exaptation process, and decoupling theories from flight and related mechanisms is important.

Climbing is only one of these features, but the absence of strong rotation of the antebrachium impairs most "forelimbs helped climb" that also precludes quadrupedalism as an avenue towards the avian stance. This requires a focus towards other components of the forelimb. WAIR (wing assisted incline running, now falling out of favor), nest coverage, the predatory two-armed strike, the development of forelimbs with excessive display structures, necessitating arm folding to keep structures like feathers or large claws out of danger, and so forth.

Cheers,  

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[Jura]

Compromised forelimbs do not necessarily imply their lack of use in prey capture. One needs to be careful about inferring use from pathological specimens. That the forelimbs showed signs of healing from some major damage could mean that the animal either took "a few weeks off" and hid away until its arms healed, favoured the healthy arm at the time (since the damages were unlikely to be simultaneous), or it switched its diet to easier to capture prey during the healing process. I'll note that Senter and Jeungst suggest all three of these as options as well. We don't really know anything of the body quality of the animal during this time, nor was there any osteohistology taken to look for signs of nutrient reallocation for healing (e.g., potential double LAGs), so we are limited in what we know of the recovery process.

— Jason

[Tim Williams]

Thomas Yazbek <yazbe...@gmail.com> wrote:

> Complete baseless amateur speculation here, but perhaps the fact that avian wings evolved from t-pod forelimbs indicates that they were *not*
> serving any function essential enough to resist selection for flight?

Not baseless speculation at all.  I'd say that's an eminently reasonable hypothesis - though I'd refine to say that the forelimbs were not serving any essential function that needed to be abandoned in order to permit selection for flight.  If the pre-flight wings were used for display, for example, this function could continue.

> There is of course the idea that the flight stroke is derived from forelimb movement for prey apprehension. But I don't know whether it's still
> considered a serious hypothesis.

I don't know either, TBH.  But if the first theropods to experiment with aerial locomotion looked anything like _Anchiornis_ or _Archaeopteryx_, this would weigh against the 'predatory stroke' being either biomechanically or ecologically ancestral to the flight stroke.

[Tim Williams]

Jura <arch...@gmail.com> wrote:

> Compromised forelimbs do not necessarily imply their lack of use in prey capture.

True.  But compromised forelimbs (for a prolonged period) not being fatal to the predator - this is consistent with a lack of use in prey capture.

> One needs to be careful about inferring use from pathological
> specimens. That the forelimbs showed signs of healing from some major damage could mean that the animal either took "a few weeks off" and hid
> away until its arms healed, favoured the healthy arm at the time (since the damages were unlikely to be simultaneous), or it switched its diet to
> easier to capture prey during the healing process.

Note that Senter and Jeungst suggest that the individual "survived for months and possibly years" in this condition.  And one finger remained permanently incapable of flexion.

> I'll note that Senter and Jeungst suggest all three of these as options as well.

Yes, the authors propose multiple scenarios by which the predator could 'get by' with damaged or incapacitated forelimbs.  But the alternative is simpler: that these pathologies had little or no impact on _Dilophosaurus_'s survival, because the forelimbs were not engaged in prey capture anyway.  So when the authors suggest that this _Dilophosaurus_ was temporarily forced into "subsisting on prey small enough to be dispatched with the mouth and/or feet alone", I'd say this could have been normal behavior.  

To paraphrase a line I read in a recent(ish) article: hunting is about catching a meal, not a prize - so most predators target juveniles.

[Sean McKelvey]

I'm admittedly an amatuer as well, and I thus could be way off the mark here, but.

Outside of a few outliers (Megaraptorans & Dromaeosaurs) most carnivorous theropod groups seem to converge on the "big head-tiny arms" bauplan. To me, that would clearly indicate that the jaws are the primary form of prey capture and manipulation. 

The hang up I have regarding the shorter armed taxa using their forelimbs in prey capture is that the skull and head would still be the first point of contact with a prey item. The only thing I can think of here is that they potentially are using the forelimbs to help hold a prey animal in place as the jaws do the dirty work, although I'm still not sure you could class that as the forelimbs being primary means of prey capture?

As others have mentioned, the fact that the pathologic Dilophosaurus didn't die relatively quickly after the injury and deformity suggests that the forelimbs, if they played any role in prey capture, were not crucial to the success of a hunt.

I may just be rambling though.

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[Alberta Claw]

An interesting perspective on wild extant sauropsids surviving the loss of what might be considered essential limb functions was put forward recently by Stroud et al. (2025). Not necessarily directly analogous to any individual case of pathology we might observe in the fossil record, but probably one to keep in mind while interpreting the function and importance of appendages in extinct organisms.

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[Thomas Yazbek]

Reviewing the replies here....

I wonder if theropod forelimbs mainly had a defensive/agonistic function...e.g. scratching interspecific and intraspecific foes. That would explain why so many taxa retain sharp claws. It is interesting that reduction of the hand occurs either in highly cursorial theropod lineages (tyrannosaurids, oviraptorosaurs, ceratosaurians, alvarezsaurs) or gigantic clades with huge heads (megalosaurids, carcharodontosaurs...). Perhaps being fast enough or big enough means no need to retain defensive forelimbs?

Of course, dromaeosaurs and ornithomimosaurs are ostensibly fast runners, but well-endowed with arms, and the gigantic spinosaurids also possess robust forelimbs. But I think these might be exceptions that prove the rule: these taxa seem to have specialized food acquisition and/or display reasons for keeping prominent forelimbs.  

Again, more amateur brain doodles. Perhaps for the giant theropods with really big heads, it just made sense to ditch the extra weight of forelimbs which were not useful in food acquisition anyways. But this doesn't explain forelimb reduction in e.g. *Limusaurus* vs ornithomimosaurs...

T. Yazbeck

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[Gregory Paul]

One avepod dinosaur that needs its forelimb function detailed is of course nestling and especially fledgling hoatzins and how they use their arms for climbing.

[Gregory Paul]

Ah yes, the good old John Ostrom hypothesis of Archie using its feather arrays as insect traps as he showed that birds and dinos. Illustrated in Dr Bobs mind blowing 1975 Scientific American article ( I wonder how many these days have even seen that, also included the first artistic rendering of a feathered dinosaur - it was a stunner at the time, although tech papers on the new dinosaur paradigm had been coming out for awhile). It was soon noted that primary feathers close up during the downstroke which precludes them from being insect catchers, and the notion was dropped by the late 70s or so as I recall. 

One item that always got my goat was illustrations of Archaeopteryx chasing dragonflies. Would not have worked. 

GSPaul

On Saturday, November 1, 2025 at 12:53:34 AM EDT, Thomas Yazbek <yazbe...@gmail.com> wrote:

Complete baseless amateur speculation here, but perhaps the fact that avian wings evolved from t-pod forelimbs indicates that they were *not* serving any function essential enough to resist selection for flight? There is of course the idea that the flight stroke is derived from forelimb movement for prey apprehension. But I don't know whether it's still considered a serious hypothesis.

T. Yazbeck

On Sat, Nov 1, 2025, 12:02 AM Tim Williams <tij...@gmail.com> wrote:

Yes, as Mike mentioned, I never said that the forelimbs of predatory theropods were useless.  I'm casting doubt on the assumption that predatory theropods used their forelimbs for catching and handling prey.

One specimen that is instructive in this regard is the _Dilophosaurus_ specimen UCMP 37302 with severely damaged and deformed forelimbs (Senter & Juengst, 2016).  The fractures healed and the _Dilophosaurus_ survived, despite the forelimbs being severely compromised.  But damaged forelimbs may have impacted other aspects of _Dilophosaurus_ life - such as breeding, if the forelimbs were used for display or intraspecific combat.

For tyrannosaurids, Zanno & Napoli note that both _Nanotyrannus_ and _Dryptosaurus_ have relatively large hands.  This theme was taken up by some news articles, in suggesting that the enlarged hands and claws of _Nanotyrannus_ would have been used for prey capture - in contrast to _Tyrannosaurus_.  I'm highly skeptical of this interpretation.  

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[Gregory Paul]

And I am way skeptical that the baso-eutyrannosaur big arms (more robust in Drypto than BM which is not Nano) were not used for prey handling, They are there, and they were much more useful than those of tyrannosaurids. And the Appalachia B-Es had kept them going until the bitter damn that asteroid and the Deccan Traps end.

Could have helped grabbing onto and bringing down those fleeing ornithomimids. 

Remember we do have evidence that some theropods used their arms for combat, as per the famed Fighting Dinosaurs (not to be confused with the Dueling Dinosaurs). 

And the amazing Battling Dinosaurs, with full grown Tyrannosaurus and Triceratops locked together in a terrible fight to the death! 

Well, one can dream;)

The TT-zone baso-eutyrannosaurs (and the family level names thing is an inherent mess, sort of like that titanosaurs thing) sporting big arms may have been a reason why it looks like they were doing a competitive number on the far less numerous actual Tyrannosaurus juveniles, which is why there are no good specimens of those yet:( Those nasty immigrants, should have had controls at the land bridge (which I note Z&N have to the south -- have seen that elsewhere and it makes sense regarding how the TT-zone was laid down, but I thought the seaway fauna indicated the fauna of the part near the US/Canadian border [soon to be eliminated of course] showed liks to the gulf.  

And it is of note that the TT-zone hyper gracile B-E's (BM and Jane) had longer lower legs than the juv Tyrannos, the Baby Bob tibia is about the same length as the femur. Also of note is that the Appalachia B-Es too had short legs. Of the TT-zone B-Es only Nano (the only specimen that can be reliably called that is the holotype) MIGHT have been like that. 

Lots of way cool science to do with MTTH having become the neoparadigm. 

GSPaul 

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[Gregory Paul]

One avepod dinosaur that needs its forelimb function detailed is of course nestling and especially fledgling hoatzins and how they use their arms for climbing.

On Friday, October 31, 2025 at 07:03:41 PM EDT, Gregory Paul <gsp...@aol.com> wrote:

[Andreas Johansson]

If there are few dead juvie Tyrannosaurus, but relative lots of adults, doesn’t that to the contrary mean that the juveniles were doing well?

—
Andreas Johansson

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[Stephen Poropat]

Not necessarily. They might have preferred habitats wherein they were less prone to burial / fossilisation. And/or their carcasses might have been more comprehensively cleaned up by scavengers before being buried. 

Dr Stephen F. Poropat

Deputy Director

Western Australian Organic and Isotope Geochemistry Centre

School of Earth and Planetary Sciences

Curtin University

Bentley, Western Australia

Australia 6102

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[Mike Habib]

Or just consumed in their entirety. We need to remember that most consumption my predators doesn’t look like National Geographic specials featuring megafauna kills on the Serengeti (including most predation in the Serengeti). Most of the time, predators catch something much smaller than themselves and eat most of it or even all of it. Those kills don’t make it into the fossil record (except sometimes as gut contents if the predator dies shortly after).

Cheers,

—Mike

Michael B. Habib, MS PhD
Research Associate, Dinosaur Institute
LA County Museum of Natural History
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On Nov 1, 2025, at 10:37 AM, Stephen Poropat <stephen...@gmail.com> wrote:



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[Gregory Paul]

Well yeah, in that enough were growing up to be mama and pappas and keep things going. 

But unlike other tyrannosaurids the juvenile populations appears to have been suppressed. 

GSPaul

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[Mike Habib]

On Nov 1, 2025, at 5:27 AM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

And I am way skeptical that the baso-eutyrannosaur big arms (more robust in Drypto than BM which is not Nano) were not used for prey handling, They are there, and they were much more useful than those of tyrannosaurids. And the Appalachia B-Es had kept them going until the bitter damn that asteroid and the Deccan Traps end.

But the arms aren’t big - they’re really quite reduced. They’re just not as reduced as in Tyrannosauridae. There’s a range of reduction in forelimbs among ratites, too, but the general pattern is still reduced function across all of them. The key is to place them evolutionary morphology in a comparative, phylogenetic context. Compared to the ancestral state, the forelimbs of base-eutyrannosaurs are noticeably reduced, in multiple ways: reduction in digit number, reduction in muscle insertion topology, reduction in element lengths (and total limb length, as a result), and reduction in element diameters (which is mechanically critical - especially because the diameters actually respond to loading *in life* - they’re not just patterned by genetics). That doesn’t mean that the animals refused to ever touch a meal with their hands - but it does run counter to a functional hypothesis of habitual utility in prey acquisition. Especially if, as was probably the case, the prey was usually quite small. 

Could have helped grabbing onto and bringing down those fleeing ornithomimids. 

I mean, maybe, if the animal missed and ran into the ornithomimid with its chest. 

Rather than speculate about what we think was possible, though, a more productive approach is to lay out (preferably quantitatively where possibly) what our predictions are under a prey-grasping model. We would expect forelimb hypertrophy, expansion of digital flexor insertions, high section modulus across all major bony elements, especially relative to the adduction plane, retention (and possibly expansion) of the semi-opposed digit of the hand, and (critically) a range of motion and reach that is commiserate with grasping a fleeing or struggling animal. None of these seem to be met - ROM still needs some work, but given that the shoulder and elbow basically have to be dislocated (and probably coupled with a complete triceps avulsion) to get the hands out near the face, I’m skeptical that in-depth ROM analysis will ultimately do anything but sink the grasping model further. 

Remember we do have evidence that some theropods used their arms for combat, as per the famed Fighting Dinosaurs (not to be confused with the Dueling Dinosaurs). 

To quote Mr. Spock: “I’m not sure that qualifies”. In the Fighting Dinosaurs, we have a theropod getting absolutely wrecked by a much stronger, larger animal, apparently flailing at it with the forelimbs, and summarily getting one of those forelimbs bitten. 

That said, use in *combat* is more consistent with the morphology than use in predation, especially for pennaraptorans. We should keep in mind that the early pennaraptoran forelimb was essentially bound up in the “skin sleeve” we still see in modern birds - there was probably a propatagium (so limited elbow extension), and the hand is essentially a series of gracile rods (metacarpals and phalanges) bound up in a muscle/ligament/integument sheath. The whole hand is rotated to be almost palm forward (the flight position of living birds). Altogether, it’s a forelimb that could definitely smack things (anyone that has been hit by the wing of a large bird knows this can really sting), but not really grab anything.

My favorite observed usage of a pennaraptoran forelimb for combat is probably in swans - they will hold terrestrial carnivorans (especially dogs) underwater and drown them. Swans are metal.

Cheers,

—Mike

Michael B. Habib, MS PhD
Research Associate, Dinosaur Institute
LA County Museum of Natural History
900 W Exposition Blvd. Los Angeles, 90007

biology...@gmail.com

+1 (443) 280-0181

And the amazing Battling Dinosaurs, with full grown Tyrannosaurus and Triceratops locked together in a terrible fight to the death! 

Well, one can dream;)

The TT-zone baso-eutyrannosaurs (and the family level names thing is an inherent mess, sort of like that titanosaurs thing) sporting big arms may have been a reason why it looks like they were doing a competitive number on the far less numerous actual Tyrannosaurus juveniles, which is why there are no good specimens of those yet:( Those nasty immigrants, should have had controls at the land bridge (which I note Z&N have to the south -- have seen that elsewhere and it makes sense regarding how the TT-zone was laid down, but I thought the seaway fauna indicated the fauna of the part near the US/Canadian border [soon to be eliminated of course] showed liks to the gulf.  

And it is of note that the TT-zone hyper gracile B-E's (BM and Jane) had longer lower legs than the juv Tyrannos, the Baby Bob tibia is about the same length as the femur. Also of note is that the Appalachia B-Es too had short legs. Of the TT-zone B-Es only Nano (the only specimen that can be reliably called that is the holotype) MIGHT have been like that. 

Lots of way cool science to do with MTTH having become the neoparadigm. 

GSPaul 

On Saturday, November 1, 2025 at 12:02:35 AM EDT, Tim Williams <tij...@gmail.com> wrote:

Yes, as Mike mentioned, I never said that the forelimbs of predatory theropods were useless.  I'm casting doubt on the assumption that predatory theropods used their forelimbs for catching and handling prey.

One specimen that is instructive in this regard is the _Dilophosaurus_ specimen UCMP 37302 with severely damaged and deformed forelimbs (Senter & Juengst, 2016).  The fractures healed and the _Dilophosaurus_ survived, despite the forelimbs being severely compromised.  But damaged forelimbs may have impacted other aspects of _Dilophosaurus_ life - such as breeding, if the forelimbs were used for display or intraspecific combat.

For tyrannosaurids, Zanno & Napoli note that both _Nanotyrannus_ and _Dryptosaurus_ have relatively large hands.  This theme was taken up by some news articles, in suggesting that the enlarged hands and claws of _Nanotyrannus_ would have been used for prey capture - in contrast to _Tyrannosaurus_.  I'm highly skeptical of this interpretation.  

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[Gregory Paul]

The below is one of the many reasons I continue to conclude those babies (deinonychosaurs, therizinosaurs, therizinosaurs) were secondarily flightless. And another example of the establishment being dug like they used to be with dinofeathers until the 1996 SVP in NYC. But I digress.

GSPaul

[Ethan Schoales]

After that paper, everyone drew Syntarsus (and only Syntarsus) feathered and crested in the same way.

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[Gregory Paul]

Sarah Landry did it. She was the go-to SciAmer illustrator. A distinctive delicate style long gone. 

The late great Richard Ellis did the eye catching Longisquama on the cover. 

GSPaul

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[Tim Williams]

One thing to remember is that powered flight is not an all-or-nothing proposition.  Certain small pennaraptorans might have engaged in various kinds of ground-based aerial locomotion behaviors that involved wings.  But only in a minority did this lead to true powered flight, including take-offs.  

Also, in certain pennaraprorans, the ability to fly might have an ontogenetic component.  For example, juvenile _Deinonychus_ might have been capable of powered flight, but adults were flightless.  Adults could still have kept their big wings for display (including agonistic behavior).

[Jaime Headden]

The problem that is leading to a rather public vitriolic response between the anti-Nano and pro-Nano groups is this rather entrenched thinking, that will likely lead to crowing if anyone concludes something in line with a presupposition, regardless of the reasons for that conclusion. That is, you'll be happy if "I was right!" even if it's not for the reasons you've argued.

"Nano isn't T. rex!"

"But some of what's been argued still is."

"Oh, there's three+ species of tyrannosaurid in the Hell Creek!"

"Well, some may not be tyrannosaurid."

"But I'm right they're not Tyrannosaurus rex!"

"But not for any of the reasons you've said."

I'm gonna be a bit of cold water for a moment:

Even if Jane is not Tyrannosaurus rex, and it seems a pretty good slam dunk it's not at this point, this doesn't mean it's Nanotyrannus. I'd almost prefer the method of coining a new binomen over supporting a new species to an established genus, if only for the avoidance of the whole "Nano real vs not" debacle, but I'm hardly one to speak on the matter. If the phylogenetic analysis is improved and moves Jane closer to rex, this issue becomes muddier and muddier, but at least all they've named was N. lethaeus. If the lancensis holotype is, as Greg himself has argued in this whole thread chain, rather bad for basing a holotype upon (and saying this only because Jane is two orders of magnitude more complete), then we've left with pining the issue of "not all juvenile/subadults in the Hell Creek are T. rex" to the Nanotyrannus debate, and without much value gained. Nanotyrannus colors these arguments horrendously. Part of the composition of issues is using the undescribed and more complete Bloody Mary to support the process of referring Jane to a new species. It seems more fitting if it was more valuable, more complete, that it be the holotype and not Jane.

If there are verifiable, publically available, collected and substantively distinct juvenile/subadult tyrannosaurs from the Hell Creek that are demonstrably T. rex, then that should have been part of this project, in my opinion; or rather, that there had been a better discriminatory analysis of the specimens to permit distinction and preclude against slapping any ol' subadult into T. rex based on precedent. But I understand that wasn't the point of the paper. Indeed, being cynical for a moment, I can't help but think that getting into the debate in the first place, ahead of Bloody Mary's description, was the point of the paper. I'm assuming Bloody Mary is the topic of Zanno and Napoli/Napoli and Zanno's talks at SVP.

(I'm still waiting for the FSAC KK-11888 "neotype" redescription so we can go back to that can of worms and get to discuss why all the variation in spine shape and snout anatomy across N. African spinosaurid material doesn't actually matter and compare processes. Won't that be fun?)

Cheers,

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[Dalton Meyer]

I would argue that the last bit there is particularly uncharitable. I wouldn't characterize this as getting into the debate ahead of the description of NCSM 40000, but rather as the necessary first step in the description process preceding a more in-depth monograph (see the description in the supplement). Regarding the assigning of Jane to Nanotyrannus, it's also something that clearly follows the line of reasoning in expanding the Nanotyrannus hypodigm. Having not investigated CMNH 7541 firsthand, I can't claim to have a tremendously informed view on the quality of the specimen, but from the data presented in the paper it appears to meet the necessary quality of retaining diagnostic features. That these features are present in NCSM 40000 establish that it must be contained within that taxon regardless of the baggage that the name brings with it. It follows then that Jane sharing the diagnostic apomorphies of Nanotyrannus (both those seen in the holotype and in the expanded hypodigm) results in it also being contained within the taxon. To me, the authors also do a good job describing and illustrating the features that distinguish Jane from the hypodigm of N. lancensis, which then necessitates the establishment of a new species. 

Regarding other fossils of juvenile tyrannosaurs from the Hell-Creek, when it comes to establishing the presence of a distinct (non- T. rex) and small bodied tyrannosaur in the ecosystem, it is equivocal to find either an undisputable juvenile T. rex or an undisputable adult (or very near adult) Nanotyrannus and this study has done the latter. In terms of now diagnosing the juvenile tyrannosaur material of the Hell Creek, that is contingent on those remains displaying the diagnostic features of either Tyrannosaurus, Nanotyrannus, or potentially being new taxa themselves. And it may be that the responsible maneuver is to be more judicious with the "indet" label than we have been historically. The supplement of this paper does have an extensive list of tyrannosaur specimens with taxonomic assignments (including juvenile T. rex) based on the author's examination, and for specimens not included I see several reasons for not including them in this study. If they do not share diagnostic features with the Nanotyrannus hypodigm, they are of little utility for a study dedicated to establishing said hypodigm. The diagnosis of that material is better served by a dedicated publication, and without knowing any of the details or stakeholders, it is also very possible that they are currently being worked on by other groups. 

 

All the best,

Dalton

[Sean McKelvey]

I agree wholeheartedly, Dalton.

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[Gregory Paul]

The below plausible scenario is involving a flight component that is the primary driving force in the evolution of dinowings in the later Jurassic. Even if it is not high level flight, descendants that have lesser flight abilities down to none are were neoflightless. 

That some large derived flightless adult dromaeosaurs were growing up from kids with some level of aerial abilities is in line with the neoflightless hypothesis. 

Why do at least do deinonychosaurs, oviraptororsoaurs, therizinosaurs have or probably had a leading edge patigium? That is a clear aerodynamic feature that improved aspects of airflow over the inner wing. 

GSPaul

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[Gregory Paul]

BM is NOT Nanotyrannus. As I showed in the Mesozoic paper (Fig. 10). Has nothing to do with radically different Nano, which just might maybe be Drypto but that is nowhere close to certain. Nor is Stygivenator a Nano. Yes the type is crap, but it is easily diagnosed as not Nano. And BM is close to Stygi. 

JH is correct that there is a danger of folks going from a paradigm of everything is T. rex to one of it ain't T. rex it is Nano. For example Z&N say that it is surprising that there are two taxa rather than just N. lancensis. No it is not, that the lesser eutyrannosaurs are taxonomically diverse has long been obvious, just look at the skulls. Let us avoid the herd mentality thing in the future. To her credit Zanno has been saying it is fine if others disagree with the details of the MTTH that they have made a major contribution to. 

Most of the actual teen Tyrannosaurus specimens are in private hands and Z&N were not going to include them. And they put the KUVP maxilla in Nano when I am pretty sure it is a Tyrannosaurus. 

Having been solidly established as the paradigm, the MTTH is now about the details. 

GSPaul

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[Gregory Paul]

The Nano type is very defective. No postcrania when items like long hands and lower legs are very important in this problem. Skull twisted so out of shape and skull roof elements missing it cannot be restored reliably in dorsal (the Carr 1999 attempt looks good but cannot be verified), and key skull roof characters not resolvable. And if Nano is Dryptosaurus then it is way way far from BM and Jane. Nano holotype is getting towards a nomen dubium, but we are stuck with it.

Jane is easily diagnosable as not Nano at least on gradistic grounds which of course are very important when determining genera and species. And BM is even further away. 

I figure and discuss the actual juvenile Tyrannsosaurus specimens in the Mesozoic paper. Longrich and Saitta also included discussions on the issue. 

GSPaul

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.

[James Napoli]

James Napoli here (first post in the DMG). Wanted to weigh in on Greg's points about the Nanotyrannus holotype and NCSM 40000. Both skulls are significantly broken with elements distorted out of position, and we are actively working on CT and synchrotron data to digitally extract every bone and re-articulate them to get a better picture of what these skulls actually looked like in life. At least one small fragment of the Nanotyrannus holotype was plastered in place upside-down, so there's clearly a lot of work to do there. It's an active and ongoing project.

Greg - I ask that you let us finish that process before you propose any taxonomic action, both to respect our priority in NCSM 40000 and because, based on preliminary results, I do think these skulls will wind up looking much more similar than they appear to right now. You know how long it takes to restore specimens with this degree of taphonomic alteration (and in CMNH 7541's case, this degree of deliberate reconstruction); we're working as fast as we can given the quality of the specimens and data available to us. And given that both share the accessory rostral palatine recess, I'm confident that NCSM 40000 and the Nano type will stay Nanotyrannus lancensis. 

[Grant Hurlburt]

It would be a great service to paleontology to restore the Cleveland skull. The endocast is like that of no known theropod. The approximate lower third of the endocast is displaced rostrally as evidenced by the pituitary gland cast relocated ventral to the anterior third of the cerebrum whereas it is ventral to the midbrain in all tyrannosaurids and indeed in most of not all non-avian dinosaurs and archosaurs

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[Gregory Paul]

Thanks for the interesting note James. Will send a message to you and Lindsay about these matters soon. 

Things are sure getting more lively now that the ETRH is not the go-to paradigm! 

GSPaul

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.

[Mike Habib]



That some large derived flightless adult dromaeosaurs were growing up from kids with some level of aerial abilities is in line with the neoflightless hypothesis. 

The secondary flightless hypothesis is an intriguing one, for sure, and I find the idea that the juveniles flew (but the adults did not) especially interesting. There is definitely some merit to the concept. The trick, of course, is this implies that flight traces back to at least the base of Pennaraptora. The only recent analysis that has recovered such a result, to my knowledge, is the O’Connor study using exclusively feather vane asymmetry. Since that’s a single predictor (and vane asymmetry may not mean what they think), it’s not an especially robust result - yet. Other lines of evidence may eventually recover the same result, though, which would be quite exciting.

Why do at least do deinonychosaurs, oviraptororsoaurs, therizinosaurs have or probably had a leading edge patigium? That is a clear aerodynamic feature that improved aspects of airflow over the inner wing. 

I do take some issue with this statement, mostly because it’s unclear what it means. I want to emphasize here that I see statements like this a lot, even in the peer reviewed literature, so this is not a jab at Greg. Rather, it’s a plea to be more precise and clear with our aeromechanics language, broadly.

The propatagium does indeed have important aeromechanical performance effects, but that doesn’t mean that it must have evolved in a flighted context. To understand why, we have to consider what the propatagium does. It has four primary performance effects:

1) It creates a dynamic leading edge on the inboard wing that has significant ability to adjust entry angle (the “improved aspects of airflow” that Greg referred to).

2) It takes up chord-wise slack in the wing when span is reduced, thereby modulating/maintaining proper aeroelastic limits (i.e., prevents the wing from fluttering too much).

3) It holds spanwise tension and passively limits ROM at the elbow and wrist, preventing overextension and contributing to ROM linkages between the elbow and wrist.

4) It provides a substantial expansion of feather attachment area, especially for coverts. 

The trick is that #4 (and maybe #3?) applies even if the animal isn’t aerial. So there is a hypothetical selection space in which a propatagium could originate and perpetuate prior to the origin of flight.

Cheers,

—Mike

Michael B. Habib, MS PhD
Research Associate, Dinosaur Institute
LA County Museum of Natural History
900 W Exposition Blvd. Los Angeles, 90007

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College of the Canyons

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On Nov 2, 2025, at 4:11 AM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:



The below plausible scenario is involving a flight component that is the primary driving force in the evolution of dinowings in the later Jurassic. Even if it is not high level flight, descendants that have lesser flight abilities down to none are were neoflightless. 

That some large derived flightless adult dromaeosaurs were growing up from kids with some level of aerial abilities is in line with the neoflightless hypothesis. 

Why do at least do deinonychosaurs, oviraptororsoaurs, therizinosaurs have or probably had a leading edge patigium? That is a clear aerodynamic feature that improved aspects of airflow over the inner wing. 

GSPaul

On Sunday, November 2, 2025 at 12:27:23 AM EDT, Tim Williams <tij...@gmail.com> wrote:

One thing to remember is that powered flight is not an all-or-nothing proposition.  Certain small pennaraptorans might have engaged in various kinds of ground-based aerial locomotion behaviors that involved wings.  But only in a minority did this lead to true powered flight, including take-offs.  

Also, in certain pennaraprorans, the ability to fly might have an ontogenetic component.  For example, juvenile _Deinonychus_ might have been capable of powered flight, but adults were flightless.  Adults could still have kept their big wings for display (including agonistic behavior).

On Sun, Nov 2, 2025 at 8:51 AM 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

The below is one of the many reasons I continue to conclude those babies (deinonychosaurs, therizinosaurs, therizinosaurs) were secondarily flightless. And another example of the establishment being dug like they used to be with dinofeathers until the 1996 SVP in NYC. But I digress.

GSPaul

On Saturday, November 1, 2025 at 03:36:49 PM EDT, Mike Habib <biology...@gmail.com> wrote:

 

We should keep in mind that the early pennaraptoran forelimb was essentially bound up in the “skin sleeve” we still see in modern birds - there was probably a propatagium (so limited elbow extension), and the hand is essentially a series of gracile rods (metacarpals and phalanges) bound up in a muscle/ligament/integument sheath. The whole hand is rotated to be almost palm forward (the flight position of living birds). 

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[Gregory Paul]

Me pretty skeptical about 4). 

GSPaul

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[Tim Williams]

Mike Habib <biology...@gmail.com> wrote:


> The secondary flightless hypothesis is an intriguing one, for sure, and I find the idea that the juveniles flew (but the adults did not) especially interesting.

Me too.  As you'll know, the idea comes from Parsons & Parsons (2015; doi:10.1371/journal.pone.0121476) regarding juvenile _Deinonychus_, based on osteological characters (and overall small body size).

[Michael Habib]

> On Nov 2, 2025, at 3:20 PM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:
>
> Me pretty skeptical about 4).
>
> GSPaul

I’m not sure what you mean about being “skeptical” regarding the attachment of the coverts to the propatagium in the avian wing. If you don’t believe me, check any anatomical text that shows a cross section, or even just do a dissection yourself - a large portion of the feather area inboard of the wrist in the avian wing is mounted to the propatagium.


—Mike

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[Gregory Paul]

Appears to be a weak hypothesis for the evolution of the structure. Could instead just have longer post inner arm feathers. 

That the propatagium first evolved for flight and. already being there and not having to be evolved, was then an exaptation for other purposes when retained in neoflightless descendants appears much more evolutionarily likely. 

GSPaul

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[Jaime Headden]

A webbing of flesh between digits does not necessarily mean that any derived function like swimming must have preceded its development for it to be exapted for swimming. This is the innate logical fallacy of begging the question: assuming that its function as we know it now must have preceded its development. We find that cats have these structures, but this doesn't mean they are by their nature aquatic, and they don't have any seemingly substantial aquatic phase preceding them. To handle this, we should try to decouple the development of a trait to its current function, as Mike was trying to suggest, looking at alternative pathways for each of those functions.

Tracking back through oviraptorosaur evolution, arms only get smaller as we get more basal taxa, unlike basal troodont-oids/dromaeosaur-oids (should they not fall together into Deinonychosauria). Since oviraptorosaurs, and other related taxa, lack the wing-like forelimb development despite having feathers, a crooked arm with a semilunate wrist (again, preceding any development of a wing in theropod evolution), and probably a propatagium, we should be much more cautious about assuming wing planform functionality to its topology. There are other potential sources for these features that can have resulted in a perfect storm on the dromaeosaur/troodontid+bird lineage, but this whole "putting the bird before the wing" model of evolution is taking a perfect storm and ignoring how messy and divergent evolution can actually get. One day, our descendants might speculate how some novel structure of our own evolution came about, assuming that because we are like this now, it was the point of all of that that came before, missing how irregular and bumpy things like the recurrent laryngeal nerve, the cruciform crural tendons, or the gradual loss of our last lower molars were.

I understand this is a pet theory, but it's one that seems to pull in all the little problems of presuming function to structures that often have nothing to do with the purpose to which they're used in later groups. If you think that Ostrom was seriously assuming that early birds were making flyswatters of their arms as the reason for wings, instead of trying to find a pathway for the development of the flight stroke, we've got a large number of early birds for which the flight stroke was very difficult, and a lot of variable gliding antecedents to presume otherwise. That is, Ostrom was wrong, but wasn't trying to be correct.

Cheers,

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[Gregory Paul]

Protoarchaeropteryids are the most basal oviraptorosaurs and they have quite large arms.

Parsimony strongly favors flight adaptations having evolved for that purpose, others are more speculative. For example all vertebrate power fliers have a propatigium, I don't think anything else does 

GSPaul

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[Tim Williams]

Jaime Headden <jaimeh...@gmail.com> wrote:

> If you think that Ostrom was seriously assuming that early birds were making flyswatters of their arms as the reason for wings, instead of trying to
> find a pathway for the development of the flight stroke, we've got a large number of early birds for which the flight stroke was very difficult, and
> a lot of variable gliding antecedents to presume otherwise. That is, Ostrom was wrong, but wasn't trying to be correct.

Ostrom's 'insect-net' hypothesis of the 1970s, and the 'predatory stroke' hypothesis of the 80' and 90s, both endeavored to explain how the prey-catching forelimb of a theropod might have been transformed into a wing.  

But if the theropod precursors of birds didn't actually use their forelimbs for prey capture, then this no longer required.  Instead, the feathered forelimb could have been used for locomotory behaviors (maneuvering, braking, balancing, leaping) that promoted the development of the wing and the incipient flight stroke.  Maybe - and not mutually exclusive - non-locomotory behaviors (courtship, agonistic) as well.

[Jaime Headden]

Time Williams wrote:

"But if the theropod precursors of birds didn't actually use their forelimbs for prey capture, then this no longer required."

I would tack agonistic behaviors into the predatory stroke, for the same reasons Mike states earlier about the fragility of the manus. Agonistic behaviors have a tendency to result in injury, and as such regions of agonistic interaction tend to be more robust, if selected for. Otherwise, they were likely indiscriminate from non-agonistic regions. Sociosexual display seems a more likely function in that case.

The elbow hardly has the rotational capability to properly engage a substrate at a high degree of angles, probably why the Dueling Dinos Velociraptor got its arm caught in a vise (jaws); while the wrist has almost no multiplanar mobility. Torsional resistance only goes so far, as does improper bending. The forelimb does look to be used to some degree in penneraptorans, with Citipati osmolskae among other theropods showing healed fractures to the forelimb, but we can't rule out causes. Oviraptorids have more robust forelimbs than most penneraptorans, but none of them show the degree of flexibility I would look for for something to engage in agonistic behaviors. Jaws and feet, for instance, which in dromaeosaurids and oviraptorids remain robust with high degrees of ungual curvature (although nothing compared to therizinosauroid pe[de]s).

I was big on WAIR when it was first proposed, because it was a natural onroad from a natural set of behaviors, although the principle motivator for its description is a derived behavior and not nascent to birds as a whole (previously mentioned in this thread, aiming to be right but for the wrong reasons; it can still be an adequate explanatory motivator for some aspects of the land to air process---which, because it's somewhat relevant to Greg's reply to me---:

Greg wrote, in response to my claim that basal oviraptorosaurs had short arms (something we also see in halszaraptorine troodontids, unenlagiines, etc.) that protarchaeopterygids had relatively long arms. This might be true of Protarchaeoptyx, but it's not true of Similicaudipteryx, or any of the other non-caegnathoid oviraptorosaurs for which we have forelimbs. Rather, they all show something that is predicted by WAIR, and has been used in other models that contradicts the nascent flight-ness of penneraptorans, or maniraptora in general: Their highly terrestrial limb and hip anatomy.).

Social functions and breeding/brooding/nesting functions, even feeding behavior such as umbrella-making for shade, seem useful, but hard to prove. The default at this point would probably be sociosexual. (Note: this does not mean the null.) I think the general thrust of this thesis leads me to think that the forelimbs of tyrannosauroids remain functionally selected for rather than vestigialized over the course of the middle and late Cretaceous because there was still a pressure to maintain well-developed unguals and digit flexibility, even functional sub-lunate wrist flexion. They weren't being selected for, as I've said before---merely that they weren't being selected against, and despite massive size growth, were not entirely removed developmentally. So there is still a pressure to keep them (apart from the functional necessity of the humerus and shoulder girdle).

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[Gregory Paul]

The wee armed caudipteygids are not the basal-most oviraptorosaurs, and they are very highly specialized extra long legged ground runners that appear in the Cretaceous long after the initiation of avian flight to beyond the Archaeopteryx level as per alcomonavians back in the Jurassic. They look like the ratites of their time -- they could have been named ratitemimids. So using them to restore the development of avian flight is highly speculative and nonparsimonius. 

GSPaul

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[Tim Williams]

Jaime Headden <jaimeh...@gmail.com> wrote:

> I would tack agonistic behaviors into the predatory stroke, for the same reasons Mike states earlier about the fragility of the manus. Agonistic
> behaviors have a tendency to result in injury, and as such regions of agonistic interaction tend to be more robust, if selected for.

I note that some modern birds (screamers, plovers, etc) have wing spurs that are used in agonistic behavior.  So the wing is used in combat and defense - despite the risk of injury to the wing.  

> I think the general thrust of this thesis leads me to think that the forelimbs of tyrannosauroids remain functionally selected for rather than
> vestigialized over the course of the middle and late Cretaceous because there was still a pressure to maintain well-developed unguals and digit
> flexibility, even functional sub-lunate wrist flexion. They weren't being selected for, as I've said before---merely that they weren't being
> selected against, and despite massive size growth, were not entirely removed developmentally. So there is still a pressure to keep them (apart
> from the functional necessity of the humerus and shoulder girdle).

Setting aside the extremely reduced forelimbs of tyrannosaurids, one hypothesis for tyrannosauroid forelimbs (e.g., _Nanotyrannus_) is agonistic behavior - presumably fairly close range.  But prey acquisition?  Unlikely, IMHO.

For pennaraptorans, I also tend not to read too much into manus morphology, including basal avialans.  For example, the manus of _Confuciusornis_ retains two fairly large recurved claws (both with well-developed flexor tubercles) on the first and third digits, whereas the robust middle digit has only a tiny claw.  I doubt this peculiar morphology reflects any specialized use of the hands by _Confuciusornis_.  Here the forelimbs are clearly wings used for powered flight.  I doubt the manual claws had any function at all, apart from possible agonistic behavior - so maybe analogous to wing-spurs, although I don't want to overstate this comparison.