For what will possibly be my last post before the big move (the blog will keep the same address, but we'll see how the Database itself is affected), Zelenitsky et al. (2012) recently reported a somewhat surprising discovery- wings in ornithomimids.
First, note it's not actually Ornithomimus edmontonicus the paper is about. The supposed secondary shaft marks are from RTMP 95.110.1, which is Dromiceiomimus* samueli. The other two, being from the Hoseshoe Canyon Formation, are probably D. brevitertius. For some reason, everybody seems to want to ignore that edmontonicus was named in 1933, while brevitertius was named in 1926 and samueli in 1928. Zelenitsky et al. follow Makovicky et al.'s (2004) Dinosauria II chapter which synonymized all of these species, but the name would still be brevitertius, not edmontonicus, as both published references state. Principle of priority people!
* Russell only placed edmontonicus in Ornithomimus because of its
long metacarpal I, and Makovicky et al. did not list any additional justification.
Yet O. velox has never been included in a published cladistic analysis
as a separate OTU, and when it is (unpublished data), it does not clade with
brevitertius (= edmontonicus) or samueli. For instance,
O. velox lacks appressed metacarpals II and III and seems to have a medial
distal condyle on metacarpal I positioned higher than its lateral condyle, both
less similar to Dromiceiomimus than Anserimimus is.
With that out of the way, vaned feathers in ornithomimids shouldn't really be that surprising. As Martyniuk (online 2012) stated, Currie and Chen (2001) noted Sinosauropteryx's seemingly stage 1 feathers were probably vaned, and there have been a few references since that discovered modern vaned feathers become difficult to diagnose as such after crushing and decay. So the supposedly simple body feathers we have in e.g. Beipiaosaurus or Scuirumimus may have originally been vaned. Pelecanimimus does have large paired sterna with ossified ribs and possibly uncinates, so maybe basal ornithomimosaurs were more flight-y anyway. Not only that, but the seemingly solid position of ornithomimosaurs outside Oviraptorosauria+Paraves isn't quite as definite as it seems. It's just that basically all recent coelurosaur matrices inherit the character bias and miscodings of the TWG matrix. So no surprise their topologies are all similar.
I was however surprised that Horseshoe Canyon and Dinosaur Park specimens could preserve feathers. The two Horseshoe Canyon specimens both show what have been commonly identified as stage 1 or 2 feathers, but which may be degraded state 3 feathers as noted above. Those on the forelimb are short, but who knows how complete they are. The Dinosaur Park specimen has been known for a while and is the source of the supposedly adult winged morphology described in the new paper. This is based on black marks on the radius and ulna which trend posterodistally to distally, and sometimes are U- or hook-shaped as if they had hollow centers. Now maybe these are feather remains, though I don't know of any other theropod which has preserved feathers this way. Yet as Mcfeeters noted on the DML, they only show the shaft, not any vane. Couldn't these just be stage 1 feathers, quills, etc.? They certainly don't indicate Zelenitsky et al.'s conclusion that adults had long wing feathers while juveniles didn't, as the length is unknown in both (>15 mm in a juvenile; >6.5 mm in an adult). Sure they're three times wider than the filaments of the juveniles, but the adult is 2.4 times as large, bases of feathers are thicker than other parts, and secondary quills are plausible without vanes.
So while the new paper is interesting in showing Dromiceiomimus had feathers and possibly thick quills/shafts on the lower arm in D. samueli, I don't think it successfully shows the genus had long secondaries, vaned secondaries, or changed its plumage ontogenetically. This makes their oft-copied figure 4A/B of the little unwinged individual and adult with ostrich-like wings possibly misleading.
References- Currie and Chen, 2001. Anatomy of Sinosauropteryx prima from Liaoning,
northeastern China. Canadian Journal of Earth Science. 38, 1705-1727.
Makovicky, Kobayashi and Currie, 2004. Ornithomimosauria. In Weishampel, Dodson
and Osmolska (eds). The Dinosauria Second Edition. University of California
Press. 861 pp.
Martyniuk, 2012 online. http://dinogoss.blogspot.com/2012/08/did-sinosauropteryx-have-protofeathers.html
McFeeters, 2012 online. http://dml.cmnh.org/2012Oct/msg00106.html
Zelenitsky, Therrien, Erickson, DeBuhr, Kobayashi, Eberth and Hadfield, 2012. Feathered non-avian dinosaurs from North America provide insight into wing origins. Science. 338(6106), 510-514.
Yes, preservation does indeed muddy the waters. I also agree that the affinities of ornithomimosaurs are precarious, especially given that AFAIK there are no Jurassic ornithomimosaurs known.
ReplyDeleteHowever, I'm intrigued by the notion that Pelecanimimus was "more flight-y" on account of its pectoral morphology (large paired sterna with ossified ribs and possibly uncinates). This interpretation sounds like the GSP approach to theropod anatomy: almost any character found in modern birds must have originally evolved for flight.
I reckon Pelecanimimus just needed stronger forelimbs - not that it was in any way "flight-y".
P.S. Can anyone send me the Alnashetri paper to tijawi@gmail.com
I've long been of the opinion that wings* probably evolved for some form of aerial locomotion, so have viewed the latter as extending down to oviraptorosaurs. Thus if ornithomimosaurs had wings, I'd say they were descended from aerial ancestors. Right now I don't think the evidence they had wings is good (contra Zelenitsky et al.), but if they did have wings and thus were potentially neo-grounded in my opinion, I was simply saying Pelecanimimus has some characters that have been associated with aerial locomotion by others. It could also just have the morphology for respiratory reasons as in Codd et al. (2007).
ReplyDelete* Have I mentioned I hate the term pennibrachia? Terms should indicate homology, not function. Or are ostriches wingless?
I used to be of the firm opinion that wings evolved for some form of aerial locomotion... but now I'm having doubts. I'm waiting on the publication of the Hall/Habib study on Microraptor using wings for turning in the air. If wings/pennibrachia did originally evolve for aerial locomotion, then I can imagine oviraptorosaurs, therizinosaurs and deinonychosaurs all being descended from a basal maniraptoran that had some kind of aerial ability. But I'm skeptical about ornithomimosaurs.
DeleteAs for pennibrachia... I think the term is OK only because "wing" is a loaded term, and intimately associated with flight. If we say a theropod has wings, then people jump to the conclusion that it could fly. A wing is a kind of pennibrachium. But a pennibrachium is not necessarily used for flight.
Of the other possibilities, brooding or display never seemed likely to me, and I'd be interested to hear a response to WAIR-doubters that that only works in galliforms and such due to them having anatomies not present in basal maniraptorans.
DeleteAnd as long as you're fine with wingless ostriches, feel free to use pennibrachium.
I'm highly skeptical of WAIR behavior in any non-avialan theropod - and in basal avialans. Galliform chicks pretty much have a complete flight apparatus - aside from the wing feathers being underdeveloped.
DeleteI think we can refer to the forelimbs of ostriches (and penguins and dodos...) as being "wings", because they evolved from wings that were used for flight. Once a wing, always a wing. But in the incipient stages exemplified by non-avian theropods ... I think avoiding the term "wing" is probably a good policy. Too much baggage.
But your use of "wing" has baggage too- by not calling Caudipteryx's structures wings for instance, you're implying it was not neoflightless. And this isn't known. Which is exactly why structures' names should reflect anatomy and not function.
DeleteNo, because pennibrachium could mean wing (i.e., used - or once used - for flight) or non-wing. This way the term (pennibrachium) is purely anatomical, and does not reflect function.
DeleteI don't know if _Caudipteryx_ was secondarily flightless (or evolved from an ancestor that used its forelimbs for aerial locomotion). But saying that _C_ had wings implies that the forelimbs were (once) used as wings.
I'd be quite happy if "wing" was reserved for members of the crown group (Aves), just as there is a trend these days to reserve the word "bird" for members of the crown group. We know the MRCA of modern birds used their wings for flight - but the more basal you go, the more dubious this assumption becomes. By the time we get to critters like _Caudipteryx_ and _Anchiornis_ or even _Microraptor_, we're on very shaky ground as to the exact function of the pennibrachia/wings.
WAIR is possible in non-avian maniraptors ... if they preserved the deltatoideus complexes, which Microraptor appearently DOES possess.
DeleteThe end result is a bat-style wing stroke, which was probably omnipresent in non-Ornithothoraces.
Likewise, Microraptor is undeniably very well adapted to aerial locomotion. That there is a controversy makes me face palm.
The issue is whether non-avian maniraptorans were capable of a full wing stroke, which is the minimum requirement for WAIR. Based on the orientation of the shoulder joint, this is very doubtful.
DeleteA bat-style elevating deltoideus (rather than supracoracoideus) does not solve the problem of humeral elevation higher than the back.
Microraptor does seem well adapted to aerial locomotion - I agree this is difficult to deny. But this aerial locomotion was likely "passive" in the sense that therw was no thrust generation, just gliding or parachuting. A SVP presentation proposed that the two sets of "wings" were used to improve aerial turning performance.
True, though even Senter agrees that the humerus could be raised more than previously thought. Whereas it would be enough is debatable.
DeleteAs for Microraptor, it seems far too specialised to be just a glider. It most likely wasn't capable of taking off from the ground, but once on the air shallow flight trokes were defenitely a possibility.
Is there a trend to only call crown Aves birds? I know there's a trend to call the crown node Aves, which I'm fine with (because it's the consensus, not because of any 'we can only be sure of so many features in the crown group' argument), but it seems silly to not call e.g. Ichthyornis a bird. Just as I don't like Gauthier and de Quieroz's attempt to limit the term pygostyle to a short structure used for retrical fans, or the thankfully decreasingly popular habit of only calling stage 4 feathers 'feathers', and calling any earlier structures 'protofeathers'.
DeleteBut say some modern bird secondarily lost caudal fusion. We wouldn't then say it had a pygostyle even under Gauthier and de Quieroz's definition. It seems equally wrong to say penguins still have wings under Sullivan et al.'s definition. If you lose aerial function, you lose your wings. Trying to save the silliness of that by saying "every descendant of a winged animal has wings" seems ad hoc.
As for WAIR, I'm no biomechanic. I do think Microraptor was at least as aerial as Archaeopteryx though, and the apparent consensus of keeping it as a glider and Archaeopteryx as a flier seems due to the latter being a bird in most peoples' minds, while the former isn't.
More aerial, actually. Archaeopteryx has short, broad wings, while Microraptor has long wings similar to those of swifts and nightjars, as well as well developed hindwings.
DeleteIf Rahonavis is of any indication, dromaeosaurs were actually better flyers than early avialans.
"As for WAIR, I'm no biomechanic. I do think Microraptor was at least as aerial as Archaeopteryx though, and the apparent consensus of keeping it as a glider and Archaeopteryx as a flier seems due to the latter being a bird in most peoples' minds, while the former isn't."
DeleteYes, I agree. This is dead hand of typology at work.
"True, though even Senter agrees that the humerus could be raised more than previously thought."
DeleteInteresting. When/where did he say that?
"As for Microraptor, it seems far too specialised to be just a glider."
The integument (feathers) was certainly specialized for aerial locomotion - I agree with you here. But the skeleton of _Microraptor_ was not specialized at all for flying or gliding. I'm not even convinced that _Microraptor_ could sprawl its hindlimbs. So to me the extensive and elaborate plumage was a sort of compensation for the lack of aerial abilities in the skeleton.
I know GSP is pretty keen on reconstructing _Microraptor_ as a powered flier (and specialized tree-dweller). But the osteological data doesn't stack up.
Some comments of his at Dinosaur Mailing List. The end result is basically that Bambiraptor being able to raise the humerus at least ten centimeters above the shoulders.
DeleteAs for Microraptor, sure, I don't doubt that it probably was not capable of extensive powered flight. However, it was certainly capable of shallow flight strokes, which would be more than enough to remain airborne for long periods of time.
I didn't know Phil Senter ever wrote to the DML. Jason Brougham has commented on humeral elevation on the DML, arguing it was more extensive (dorsally) than Senter has inferred. Or at least, he (Brougham) has argued there is enough 'wiggle-room' in the methods used to determine the orientation of the humerus to accommodate some dorsal excursion of the humerus. He makes a good point, IMHO.
DeletePersonally, I doubt Microraptor was capable of a thrust-generating wing stroke (even a shallow/rudimentary one). But it's something we may never know for sure.
Just to clarify a somewhat minor point, a lot of people seem to be misusing the term 'vaned' in relation to this story. I never (not did Currie & Chen) suggested S. prima hd band feathers--rather their study shows it had *pennaceous* feathers. Pennaceous /= vaned, it just means it has a rachis and barbs. A vaned feather requires barbules to hold the barbs together into a planar vane. I suspect there's some confusion as most pennaceous feathers in modern birds are also vaned, and with people confusing vane (the planar surface formed by barbs) with vein (i.e. the central shaft formed by the rachis).
ReplyDeleteAgree on all counts about the lack of decent evidence for remiges in ornithomimids at the moment though! It wouldn't be that surprising, but I'd like to see an actual fossilized, vaned remix first. We already know Beipiaosaurus had (probably) pennacous but unvaned "wings" if you want to call them them that. There's also been the suggestion (by Foth maybe?) that the "EBFFs" in B. inexpectus are taphonomically distorted vaned feathers.
I suppose I wasn't making that distinction, true. I should have also realized that Zelenitsky et al. claimed the lower arm shaft marks were coverts, not secondaries. Not that it changes my argument.
DeleteSo vaned = bipinnate then.
ReplyDelete