Steve Sweetman and I have just published a paper on a new maniraptoran theropod dinosaur from the Lower Cretaceous Wealden Supergroup of East Sussex, England (Naish & Sweetman 2011).
As you might know if you're a regular reader, much of my technical work has been devoted to Wealden theropods and I publish papers on them fairly regularly (recent articles: Benson et al. (2009), Naish (2010); see links below). I still have yet to publish one of my most significant contributions - the monographic description of the tyrannosauroid Eotyrannus lengi (the follow-up to the rushed and preliminary Hutt et al. (2001) paper) - but let's not talk about that. A large, state-of-the-art revision of Wealden theropods was submitted earlier this year and has been through review and accepted for publication.
I make no secret of the fact that many of the fossils I publish on are extremely fragmentary, in many cases being single bones. Identifications made on the basis of single bones can very occasionally be horribly, horribly wrong (one personal example: a cervical vertebra that I identified as oviraptorosaurian (Naish & Martill 2002) now seems to be from an abelisauroid), but they can often be made with confidence if the material is good enough, and if it preserves the required informative bits of anatomy.
A new Wealden fauna
Such is the case with the new specimen. It's a single cervical vertebra, discovered by local collector Dave Brockhurst at Ashdown Brickworks near Bexhill [adjacent photo shows me at the site, 2006]. Unlike most of the familiar Wealden dinosaur fossils, it isn't from the Wealden Group of the Isle of Wight, but from the rather older Hastings Group, and specifically from the Wadhurst Clay Formation [for help with the stratigraphic terms and their relations to one another, see the diagram below]. This unit dates to the early part of the Valanginian in the Early Cretaceous and hence is about 12 million years older than the Isle of Wight's dinosaur-bearing Wessex Formation.
Those who care about Wealden stratigraphy and Lower Cretaceous fossils will note that we're now using the term 'Hastings Group', rather than 'Hastings Beds Group', for this unit. Theropod remains are rather rare in the Hastings Group. Becklespinax and Valdoraptor come from Hastings Group units as do a number of baryonychine teeth (so does another of 'my' dinosaurs: weirdo sauropod Xenoposeidon), but all other Hastings Group theropod fossils are scrappy, indeterminate bits and pieces.
The Ashdown Brickworks locality is a new one for dinosaurs and other Cretaceous animals (at least so far as the technical published literature is concerned), and one of the things Steve and I do in our paper is draw attention to the diverse fauna recovered from the site. In addition to hybodont sharks and various other fishes, there are several (new) salamanders and anurans, assorted lizards (including skinks and an aigialosaur), and the remains of turtles, crocodilians, a plesiosaur, an ornithocheiroid pterosaur, thyreophorans, iguanodonts and theropods, including Baryonyx and an allosauroid (Naish & Sweetman 2011). That's a very representative selection of Wealden vertebrates. Incidentally, I have big projects in the works on Wealden plesiosaurs and crocodilians and will be discussing them at length at some point in the near future.
The Ashdown maniraptoran
Anyway, the big deal about the Ashdown maniraptoran [shown here, in all views] is its size. It's tiny - the whole vertebra has a total length of 7.1 mm - and the absence of any discernible neurocentral suture indicates that the animal the vertebra belonged to was skeletally mature. An adult.
Before discussing size further, let me note that the maniraptoran identification is pretty sound. On first seeing the vertebra, I was struck by the X-like shape of the neural arch (as seen in dorsal view), the large hypapophysis (a prominent keel located on the midline of the ventral surface) and the presence of fossae on the sides of the neural arch. It looked immediately like a maniraptoran cervical vertebra, especially that of an oviraptorosaur. This was confirmed by other details, like the shapes of the articular surfaces, the positions of the parapophyses, the shapes of the zygapophyses and so on. The presence of a rather large hypapophysis, combined with the position of the parapophyses (low down on the centrum), shows that the Ashdown maniraptoran vertebra is a posterior cervical: that is, a vertebra from near the base of the neck.
Having identified the specimen as from a maniraptoran, can we go further? The X-like shape of the neural arch gives the vertebra an oviraptorosaur-like appearance, and various other features are consistent with such an identification. Meanwhile, the proportionally large neural canal makes it bird-like. As we argue in the paper, however, the proportionally large neural canal seen in birds may be a size-related feature rather than a specific character of Avialae. For now, it seems most prudent to identify the specimen as Maniraptora indet., though I do suspect that it's from an oviraptorosaur or oviraptorosaur-like taxon. Before committing to anything in print, Steve and I showed the specimen to a few other theropod specialists, and I'm pleased to say that they agreed with our determination in entirety.
Small, but how small?
So, what about the size of this animal? We're careful throughout the article (Naish & Sweetman 2011) to note that determining total length from just a single bone is highly speculative. Nevertheless, it seems wrong not to at least provide a rough estimate. We used two techniques to provide a rough estimate of size; neither is particularly reliable and one is almost wholly intuitive.
The intuitive method involved duplicating modified digital versions of the vertebra to make an 'articulated' neck (the digital vertebrae were modified since vertebrae within a neck are not all the same length). Said neck was then positioned within the silhouette of a generic, oviraptorosaur-like maniraptoran. This is definitely more art than science and I'm sure that it will make some people vomit with rage. It relies on the massive assumption that the silhouette is correct to begin with. I expect to be pelted with fruit, hit in the stomach etc. when next I go on the street (sigh, after the giant tortoise incident I sure am owed a good beating). Anyway, whatever, the resulting scaled silhouette was about 45 cm long.
A second technique also involved that reconstructed neck, but this time we worked out how neck length compared to total skeletal length (TSL). I'm going to use 'TSL' here in order to make it clear that the lengths being discussed don't involve tail plumage. Neck length is not that variable across non-neornithine maniraptorans. In the oviraptorosaur Caudipteryx the neck accounts for c. 24% of TSL while it's c. 20% of TSL in short-tailed birds like Confuciusornis and c. 16% of TSL in the long-tailed bird Archaeopteryx (the paper erroneously states that neck length is c. 47% of TSL in Archaeopteryx: this is completely wrong and I'm currently trying to get it fixed). If proportioned like Caudipteryx, the Ashdown maniraptoran could have been c. 33 cm in TSL. 40 cm is about right if it was built like a short-tailed bird, and c. 50 cm is right if it was proportioned like Archaeopteryx. Because I'm leaning slightly toward the oviraptorosaur identification, c. 33 cm is looking most likely, but a ballpark of 33-50 cm is the range we're looking at.
And that's pretty interesting, because it makes the Ashdown maniraptoran one of the smallest Mesozoic dinosaurs reported so far. Excluding Epidendrosaurus (c. 16 cm TSL) and Epidexipteryx (c. 25 cm TSL) - for both are regarded as juveniles or subadults - the smallest non-avialian theropod is currently Anchiornis, with a TSL of between 34 and 40 cm (depending on whose estimate you follow). A few other small non-avialian theropods were between 40 and 50 cm: Parvicursor, Mahakala, Mei and Jinfengopteryx are among them (and, no, Compsognathus isn't one of them any more). Some of these mini-theropods are shown here, with Pioneer Dork for scale [by Matt Martyniuk, from wikipedia]. The point I'm making here is that the Ashdown maniraptoran may well be one of the smallest non-avialian theropods we know of, possibly even the smallest. Please note the many, many caveats, however.
On a similar note, this fossil is a bit of a joke when you remember that such localities as Liaoning in China are revealing 100% complete, fully articulated, fully feathered maniraptoran skeletons. However, while these fossils are, clearly, awesome, the fact that they're so awesome doesn't mean that we shouldn't be putting crappy fossils on record too. And we live in hope that more substantial remains of our tiny Ashdown maniraptoran will be found one day.
And it isn't lost on me that this is, like, the fourth paper I've published that involves analysis of a single vertebra: Ashdown maniraptoran (Naish & Sweetman 2011), Xenoposeidon (Taylor & Naish 2007), 'Angloposeidon' (Naish et al. 2004) and Thecocoelurus (Naish & Martill 2002) [in composite below, images very much not to scale]. Yikes. I might get a reputation.
Because Naish & Sweetman (2011) has been online for a while (as an in-press manuscript*), it's been covered by a few bloggers already: there's brief coverage at Beasts Evolved (though ignore the fact that the specimen is said to be from the Isle of Wight), Palaeoblog and Theropoda.
* Grumble grumble. I so hate the fact that journals put in-press/unpublished manuscripts online.
For previous Tet Zoo articles on Wealden theropods and other Wealden dinosaurs, see...
- The world's most amazing sauropod (Xenoposeidon)
- Of Becklespinax and Valdoraptor
- Where the scelidosaurs and iguanodontians roam
- Oh no, not another new Wealden theropod!
- My dinosaur colouring book # 2 (Wessex Formation dinosaurs)
- Concavenator: an incredible allosauroid with a weird sail (or hump)... and proto-feathers?
- The explosion of Iguanodon at Scientific American
- Goodbye super-inclusive Iguanodon, hello Mantellisaurus, Owenodon, Dakotadon, Dollodon, Barilium, Kukufeldia, Hypselospinus, Sellacoxa, Proplanicoxa etc. etc.
Refs - -
Benson, R. B. J., Brusatte, S. L., Hutt, S. & Naish, D. 2009. A new large basal tetanuran (Dinosauria: Theropoda) from the Wessex Formation (Barremian) of the Isle of Wight, England. Journal of Vertebrate Paleontology 29, 612-615.
Hutt, S., Naish, D., Martill, D. M., Barker, M. J. & Newbery, P. 2001. A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22, 227-242.
Naish, D. 2010. Pneumaticity, the early years: Wealden Supergroup dinosaurs and the hypothesis of saurischian pneumaticity. In Moody, R. T. J., Buffetaut, E., Naish, D. & Martill, D. M. (eds) Dinosaurs and Other Extinct Saurians: A Historical Perspective. Geological Society, London, Special Publications 343, pp. 229-236.
- . & Martill, D. M. 2002. A reappraisal of Thecocoelurus daviesi (Dinosauria: Theropoda) from the Early Cretaceous of the Isle of Wight. Proceedings of the Geologists' Association 113, 23-30.
- ., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe's largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.
Naish, D., & Sweetman, S. C. (2011). A tiny maniraptoran dinosaur in the Lower Cretaceous Hastings Group: evidence from a new vertebrate-bearing locality in south-east England. Cretaceous Research, 32, 464-471 : 10.1016/j.cretres.2011.03.001
Taylor, M. P. & Naish, D. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50, 1547-1564.
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Wow, assuming that this is truly an adult oviraptorosaur, those critters definately ram the gamut of sizes if you consider that *Gigantoraptor* is at the other end of the spectrum. Undoubtedly this further muddies the water considering the ecology of oviraptorosaurs.
Congratulations with publishing a new dinosaur, even if it is nameless.
"there's brief coverage at Beasts Evolved (though ignore the fact that the specimen is said to be from the Isle of Wight)"
I've just corrected that mistake.
Very nice diagram of a liquid metal terminator riding a dinosaur. Hard to tell exactly how it grips the reins being in such an amorphous state.
It's also nice to know our future robot overlords use their time travel for leisure pursuits, rather than just killing their enemies' parents.
Darren - how does one tell the difference between a Therepod and a Bird nowadays?
And do you believe that some Therepods, such as Velociraptor, are flightless descendants of Protobirds?
[from Darren: sorry, delayed by spam filter]
Identifications made on the basis of single bones can very occasionally be horribly, horribly wrong
The weirdest one I heard of was an azhdarchid vertebra identified as a wing bone! The weirdest part of that was that they managed to get the taxon right while simultaneously getting the part of the body so badly wrong. It did make me more sceptical of stories of the supposed Henry Higgins-like ability of biologists to reconstruct an animal based on a glance at a single bone.
As far as names go, I have some ideas, like Picoraptor angolensis (tiny snatcher from England), or maybe Emaniopteryx mirabilis (spread-winged wonder).
Total offtopic: anybody knows whether any tetrapods other than seals can detect water turbulences made by prey from distance? In particular, whether birds like Spoonbill can. :) :) :)
A question from the cheap seats:
If we know that something like this was pattering around in the underbrush (or on the lakeshore, or among the dunes), is it reasonable to assume that the local big dinosaurs were not producing large numbers of small, independent offspring?
Robert, the current evidence suggest that birds share a common ancestry with dromeosaurs and troodontids.
Sorry. Accidently posted early. Avialae includes Aves and their closest relatives. They are all believed to be descended from a common ancestor. Velociraptor inherited it's feathers from the same dinosaurs birds did.
Jenny Islander--
This critter is smaller than a cat! Maybe even hatchlings of big dinosaurs would be larger than its usual prey. (But it might have been a real menace to mouse-sized mammals like Aegialodon.)
I was thinking more that sending the young off to fill their own tiny niche wouldn't work if there was already something else living there that might be better at exploiting that niche, if for no other reason than being older on average, therefore with a greater store of experience.
[from Darren: sorry, delayed by spam filter]
The X-shape of the zygapophyses when arrayed in dorsal or ventral view is fairly common in maniraptorans; what seems particular for oviraptorosaurians, but is not exclusive to them, is the expansion of the distal zygapophyses, all of them, and has been termed "paddle-shaped," although it should be noted that this is known in basal therizinosauroids and alvarezsaurs as well as oviraptorosaurs. And while the former above have been occasionally allied to oviraptorosaurs, thus concreting the similarities, that they are in alvarezsaurs as well is particularly problematic. An array of cervical pneumatic foramina should, however, qualify oviraptorosaurs at small size, as they all have them, rather than simple shallow depressions (or "fossae"). The real kicker is in the presence of the very large hypapophysis, which is pretty strong evidence for oviraptorosaurian identity, and is one of the stronger features that links Avimimus to oviraptorosaurs. However, much of the compared taxa noted are basal, very small, and in much larger levels of completeness, thus allowing their features to be put into context; this also allows in cases where limbs may be known to track relative fusion and thus track relative age. Vertebrae alone should not be that useful to assessing age.
On a minor point, how is "Wealden" pronounced?
Jenny Islander (re #11)--
Sorry, misunderstood. ... Young of large herbivores might not be in competition with small carnivor/insectivore/omnivore, but yes, I can see that the young of large carnivores might have a problem.
I know nothing about anything, and less than that about growth patterns in theropod vertebrae, but is there any way of determining that this is an adult, rather than a juvenile (chick?) of something bigger?
:-D :-D :-D :-D :-D
Day saved!
As Darren wrote: the neural arch is fully fused to the centrum. In tetrapods generally, this indicates the animal was fully skeletally maturity or close to it and wasn't going to continue to grow a lot.
Heh!
Yeah, next you'll probably tell us that you plan to start a new blog (maybe together with a couple of colleagues) that is devoted only to dinosaur vertebrae. Oh, wait...
Sugestions:
Raptoriculus angliterrae (Small Raptor from England)
Minimiraptor liliputianus (Minimum raptor, liliputian)
or, try to find the Old English etymology of Hastings or Wadhurst, and translate it to Latin.
ps: It's interesting the possibily of an English abelisauroid...
Thanks to all for comments. Brief response to Jaime (comment 13)...
I agree that an x-type shape of the neural arch is not unique to oviraptorosaurs, but "expansion of the distal zygapophyses" (what the hell is a 'distal zygapophysis'?) is not present across oviraptorosaurs (look at Microvenator), nor is an "array of cervical pneumatic foramina" (Caudipteryx seems to lack pneumatic fossae and foramina on its cervicals; Similicaudipteryx seems to have pneumatic foramina on one vertebra at the base of the neck but not on any of the others).
As for the other stuff you say, I'm not sure if you're agreeing with my suggested identification or disagreeing with it (a problem I often have with your arguments!), but thanks anyway :)
One more point: the small species within pneumatic dinosaur clades seem to be the least pneumatic. A theoretical tiny oviraptorosaur would thus likely not have the same degree of vertebral pneumatisation as larger taxa. This prediction seems to be supported by the caudipterids, but we'd make it even if we were unaware of such animals.
Uh, Darren, I hope you just meant to write 'caudipterygids' in that last comment...?
Proud to say I've also written a paper on a single vertebra, an aquatic ophidiomorph lizard from the antipodean late Albian. So I couldn't help noticing that reference to a Hastings Group aigialosaur. Since the Jurassic Proaigialosaurus specimen was lost and the taxon apparently can't be reliably identified, while most of those sorts of things are Cenomanian, that makes a Valanginian record pretty interesting. Can we have more details when Sweetman and Evans' chapter comes out?
And I must mention Cryptolacerta hassiaca in case anyone missed last week's 'Nature' (Müller et al. 2011). Only Eocene, but still pretty significant if you like filling in 'macroevolutionary' gaps. Stubby little thing, for a basal amphisbaenian (built more like a diplodactylin gecko than a pygopod, one might say). I thought I recognised it, and just checked: there was a decent photo of the type-and-only specimen on p. 127 of Keller and Schaal (1988).
Keller, T., and S. Schaal. 1988. Schuppenechsen - Reptilien auf Erfolgskurs. Pp. 121-133 in S. Schaal and W. Ziegler, ed. Messel - Ein Schaufenster in die Geschichte der Erde und des Lebens. Valdemar Kramer, Frankfurt am Main.
Müller, Johannes; Christy A. Hipsley, Jason J. Head, Nikolay Kardjilov, André Hilger, Michael Wuttke and Robert R. Reisz (2011). "Eocene lizard from Germany reveals amphisbaenian origins". Nature 473: 364â367. doi:10.1038/nature09919
Unfortunately, 'Caudipteridae' is the 'family-level' name as originally formulated...
He, T., Wang, X.-L. & Zhou, Z.-H. 2008. A new genus and species of caudipterid dinosaur from the Lower Cretaceous Jiufotang Formation of western Liaoning, China. Vertebrata PalAsiatica 46, 178-189.
And I'm pleased somebody noticed the mention of an aigialosaur :) The Sweetman & Evans article is in the Pal Ass Wealden field guide, due to appear 2012. The last chapter... penned by myself and a mutual colleague of ours (yes, John, that's you and I)... is due to be turned in any day now.
I'm afraid angolensis means "from Angola". For an English critter, anglicus would be more appropriate.
But I presume Messrs Naish and Sweetman concluded it was to indeterminate to deserve a formal name. Plus, I've never really warmed to dino names in -raptor. Maybe we should just give it a nickname, I dunno, the Deacon perhaps?
Vasha,
"Chumley"
Wheel-den.
"the small species within pneumatic dinosaur clades seem to be the least pneumatic."
Has this been graphed? Also, might this suggest that pneumaticity originally evolved for the purpose of reducing weight in large animals?
Yay, Wealden plesiosaurs!
Wow! Thanks! Must try to download the paper...
Ashdown (OE Aescesdun), name of the place, means Hill of the Ash-tree, so, in Greek would be Meliolophus, in Latin Fraxinicollis or Ornicollis. So, could be named Ornicollia, that means "from the Ash Hill", coincidentally resembling ornis "bird" (Greek) and collum "neck" (Latin)
Darren, there may be a slight misunderstanding, though I do not think my phrasing is particularly confusing.
First, however, I'd like to note that I am neither disagreeing nor agreeing, but am remarking to clarify some statements you made. Incidentally, while I hesitate to discuss in press papers, these comments are restricted to what you write HERE. (And yes, I've read the paper itself, which establishes the vertebra in clear detail.)
When I wrote, "expansion of the distal zygapophyses," I clarified when I really wrote:
In which 1) the use of "distal" is directional, not partitioning, and 2) the aspect or form is implied (or perhaps "clarified") in the following clause. In this case, a stable morphology of oviraptorosaur zygapophyseal morphology there isn't, indicating a problem with associating such morphology when you write:
When I discussed the array of cervical foramina, it should be noted that virtually all (I give myself room to weasel out in case an oviraptorosaur manages to vanish its foramina) oviraptorosaurs appear to have some pneumatic foramina on or near the neurocentral suture and/or immediately behind the parapophysis in the posterior cerivcals/anterior dorsals, those where the hypapophysis is most distinct. You did not seem to disagree with this.
I will eventually discuss oviraptorosaur necks on my own blog, so a fuller reply on this matter will be there, where I don't have to clog your responses with my gibberish.
Hi Jaime. 'Distal' means 'furthest away from the centre of the body', so... what is a 'distal zygapophysis'? Maybe a prezygapophysis? Ok, so I understand that some people use 'distal' to mean 'furthest away from the 'body' of the element I'm talking about' - this explains why you get people talking about the 'distal end' of the pubis, or the 'distal edge' of the scapula - but that's still problematic, as some anatomical texts (the NAA and so on) say that 'distal' can only be used for appendages (limbs, the tail etc.). You were referring to the posterior parts of the postzygapophyses I think.
On cervical foramina... yes, most oviraptorosaurs have them. But, not, it seems Caudipteryx and Similicaudipteryx at least (viz, small, basal taxa). Like I said, the small bodied members of maniraptoran clades tend to be the least pneumatic, with many of their vertebrae apneumatic.
[from Darren: sorry, delayed by spam filter]
Darren, I use "distal" in this sense as identical to the phrase "distal end of," for as there is only one set of prezygapophyses to deal with, I presumed impossible to confuse a "distal" anything with another set when I was talking about a singular object. Could I have used "distal end of" instead? Sure, but I didn't and that's my fault. Not sure I would NEED to, simply because the term "distal" can be used for directions within an object just as they can be used to segregate that object in the main:
"the distal prezygapophysis" and "the distal end of the prezygapophysis" can refer to two different things, one being a general direction, the other being a segment of the prezygapophysis which may be otherwise explicitly defined. The term "paddle-shaped" being applied here should have clarified this, and I think the confusion on the matter is being overblown. (Or maybe I just don't understand.)
Similicaudipteryx yixianensis has cervical pneumatic foramina, as you yourself noted, but the issue is not quite that simple, and I will explain when your paper is published. Caudipteryx (spp.) is stated in various phylogenetic analyses, although not in the texts of various works, to have pneumatic foramina. I'd verify this personally through direct examination or by proxy (by photo), but damage to the vertebrae of the cervicals of virtually all specimens makes this difficult to assess.
Pleurocoels are consistently said to exist in the dorsals, at least the anterior ones, while dorsal neural arches are consistently pneumatized with several infradiapophyseal fossae. Are they tiny little slits in the centra? No, but this is easier to check than cervicals, which are often crushed but which some indicate small vacuities that MAY be foramina. I thus take it that where examination allows, and given a nod to authority (checking the latest versions of the Theropod Working Group Matrix, flawed as it may be, supports this, as several of its authors and its originator Xu and Norell have personally examined the relevant material) that Caudipteryx (spp.) have cervical and dorsal pneumatic foramina. I'm willing to be contradicted by solid data, though.
Thanks for comment, Jaime. I didn't realise you were talking about the 'distal end' of the prezygapophyses. If you were (I'm still confused by what you're describing, but let's not worry about it), I hope you can see that the terminology you're employing doesn't make sense. Caudipterid oviraptorosaurs lack pneumatic foramina on all or most of their cervical vertebrae (we're talking about pneumatic foramina on the centra here, not fossae on the neural arches). Like I said, this is typical for small maniraptorans. I've examined Caudipteryx and various other Liaoning maniraptorans first-hand and have discussed this matter with a few other people interested in theropods and pneumaticity.
Darren,
In regards to caudipterids, and respecting Mickey's suggestion and support that Similicaudipteryx is a caenagnathid, so that its possession of cervical foramina of the centra, I will defer to you in that you fail to find pneumatic foramina on the centra. This does not mean the vertebrae are not pneumatic. You argue above that the vertebrae themselves are not pneumatic, not restricting this comment to the centra:
comment #20: "Caudipteryx seems to lack pneumatic fossae and foramina on its cervicals; Similicaudipteryx seems to have pneumatic foramina on one vertebra at the base of the neck but not on any of the others[.]"
In this case, they are pneumatic, but lack foramina of the centra (where it's possible to observe them). However, of the some odd 30+ oviraptorosaurs, only one small group, comprised of about 5 skeletons at present, lack these foramina; one, the type of Caudipteryx dongi (= Caudipteryx zoui?) lacks cervical and anterior dorsal vertebrae, and cannot be assessed. Caudipterids are also nested among a group of theropods in which the cervicals consistently bear foramina in the centra (therizinosauroids, ornithomimosaurians, dromaeosaurids, troodontids, etc.), and with one specimen (IVPP V12430, possibly a new species of Caudipteryx) the centra are only 1.2cm long, but apparently lack foramina. In Buitreraptor gonzalezorum, the posterior cervicals are only 2cm long and bear foramina, while IVPP V17608, holotype of Linhenykus monodactylus (xu et al., 2011, you know the reference) has posterior cervical vertebrae are nearly the same size as the Ashdown vertebra, but bear pneumatic foramina (which continue into the dorsal series). The larger Mononykus olecranus -- based on MPC 107/6 -- has vertebrae only twice the length of the Ashdown vertebra, but lack pneumatic foramina. This tells me that size doesn't play that much of a role here.
To date, I know of no qualifying system that differentiates pneumatism in general from the existence of specific foramina, merely differentiating a single pair from double, and I would think that introducing such qualification would be useful. I think Mickey does this, I hope Andrea does this in his matrix.
What were we arguing about again?
I would say "merrily debating." But specifically, the value of my statement:
"An array of cervical pneumatic foramina should, however, qualify oviraptorosaurs at small size, as they all have them, rather than simple shallow depressions (or "fossae")."
You contested this with a comment about caudipterids, etc. I'd say I was wrong in the "all of them" bit. But in my defense, we're talking 2 out of 30 or so taxa.
I just noticed this at the MSNBC site:
â http://www.msnbc.msn.com/id/43356481/
For some reason, they decided to illustrate it with none of the images from the paper or this page...
Ah. The original site of the story has a caption for the image that explains the context (that the pterosaur is diving at Anchiornis, which is a contender for "smallest dinosaur").
â http://news.discovery.com/animals/worlds-smallest-dinosaur-predator-110…
They've used Mark Witton's image of Darwinopterus pursuing a small maniraptoran, but have rotated the pic so that it's shown on its side! (that white triangular thing in the background is a waterfall).
My promised response is available, posting here for continuity.