Wednesday, 27 November 2013

The Bizarre Deinocheirus.....


 
Deinocheirus mirificus – a dinosaur that we are all familiar with and now, thanks to the disclosures at this year’s SVP meeting in Los Angeles, an animal that we are now much more able to visualise in life. I first learnt about Deinocheirus as a kid and I was mystified by the huge arms of the type specimen. For me, at the time, it represented the ultimate theropod but for palaeontologists it was inconceivable that the rest of the animal could be simply scaled up from the huge arms as you might restore a conventional theropod - it was just too big.
There was even a train of thought that Deinocheirus was a kind of giant reptilian sloth using its arms to pull down vegetation. Eventually, as the science of phylogenetics came to the fore, we got nearer to the truth and Deinocheirus was generally regarded as a basal ornithomimosaur but even then there were still discussions about whether this diagnosis was accurate and a few of us were always secretly hoping that it would indeed turn out to be some kind of super predator. One thing that everybody agreed on – we needed more fossils.
Eventually they were found and Yuong-Nam Lee, of the Korean Institute of Geoscience & Mineral Resources, and colleagues presented their findings to a large and expectant audience. Two specimens were displayed – MPC-D 100/127 and MPC-D 100/128 – recovered from the Upper Cretaceous Nemegt Formation at Altan Uul IV and BuginTsav in 2006 and 2009 respectively. Much of the missing post cranial material that had eluded fossil hunters of the years was recovered although one of the specimens had already been illegally plundered which is both disturbing and unfortunate to say the least.
Of the material that was displayed there were a series of cervical vertebrae in full articulation complete with the atlas vertebra (C3 – C10) which are very ornithomimosaur-like and a similar series of dorsal vertebrae which display tall anterodorsally facing and highly pneumatic neural spines. The dorsal ribs are fairly straight and are indicative of a narrow body.  The sacral vertebrae (S1 – S6) also demonstrate tall neural spines and are fused (except for sacrals S1 and S6) and form a strong plate of bone.  This appears to demonstrate the presence of a hump in Deinocheirus akin to those found in other dinosaurs and is somewhat unexpected in this taxon.
There is also a series of caudal vertebrae preserved whilst the ilium is quite distinct and displays a raised anterior dorsal margin. The pubic region, as a whole, is strongly developed. The femur is well developed, robust and longer than the tibia and is clearly both unique and diagnostic of Deinocheirus.  Also of interest is the presence of gastroliths in the gastralia of MPC-D 100/127 (well over a 1000) and this is indicative that the animal was probably herbivorous.
Despite the fact that there is still no skull material for Deinocheirus, this new post cranial material looks wonderfully preserved and has allowed us to confirm that Deinocheirus is indeed a basal ornithomimosaur and is, therefore, a stunning vindication and endorsement of phylogenetics – a real triumph. The real surprise, however, is the visual reconstruction of the animal that drew audible gasps from the enthralled audience. There are a number of reconstructions already circulating but, in my opinion, not one of these has got the proportions or appearance of the animal correct.
I do not intend to add further fuel to the fire, and I am certainly not talented enough to produce my own image but if I said to you that Deinocheirus looks like a cross between an ornithomimid, a therizinosaur and Concavenator then you will appreciate just what a bizarre animal this really is. We all look forward to the paper which, at time of writing, still unfortunately appears to be some way off.
Next up - tyrannosaurids but before that I will be publishing a guest post which is a terrific article about the filming at the Natural History Museum in London for David Attenborough’s new programme, David Attenborough’s Natural History Museum Alive 3D, to be broadcast on New Year’s Day so watch out for this one.
Reference
Lee, Y., Barsbold, R., Currie, P., Kobayashi, Y. & Lee, H. 2013. New specimens of Deinocheirus mirificus from the Late Cretaceous of Mongolia.  Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2013, pp161.

15 comments:

Andrea Cau said...

"a series of cervical vertebrae in full articulation complete with the atlas vertebra (C3 – C10)".
Great to read that the whole cervical series is preserved!

"The femur is well developed, robust and longer than the tibia and is clearly both unique and diagnostic of Deinocheirus."
This is not surprising, since femur/tibia ratio increases allometrically with size in theropods.

"There are a number of reconstructions already circulating but, in my opinion, not one of these has got the proportions or appearance of the animal correct."
Well said!

Alessio said...

Yeah, it turned out way stranger than many always assumed.

Eagerly waiting for the official paper to be available, i want to draw a restorarion of this guy but as you said, until i have the pics of the bones under my eyes it's better to be cautious, especially regarding the "hump".

emailmark said...

Nice post Mark-like you I have often stared awestruck at those arms. Speaking of which, the dust evident in your photo is an absolute disgrace - good job the real fossils are behind glass!.

Duane Nash said...

Hi Mark, you are right about how off all the reconstructions floating around are. What I remember most vividly was how the ribcage/thorax/hips were highly modified from the typically more horizontal posture of theropods to a more vertically orientated design. Like you mentioned more convergent with therizinosaurs. And was the tail a bit short if I recall?

AnJaCo said...

"a stunning vindication and endorsement of phylogenetics – a real triumph."

Oh please. Don't get me started...
Ostrom (and others?) had it pegged long ago.

Mark Wildman said...

Thanks for the comments everyone!

@ Mark - To be fair this is a "stock" shot that I took at the NHM back in 2010 when all of the display specimens were all pretty grubby but there has been a cleaning session or two since then so the situation improved. We will take another look when we visit you and the collections next month.

@ Duane - I believe you have a point about the shortened tail but, for the life of me, I cannot recall how much of the caudal string was preserved so, again, we will have to wait for the paper.

@ AnJaCo - What is there to get started about? Phylogenetics merely built upon the observations of others and put both perspective and methodology behind the hypothesis. Without new material there was always going to be a question mark over any analysis - phylogenetic or otherwise. It still does not take away the fact Deinocheirus has been predicted to be a basal ornithomimosaur for many years now - and that earlier work has now been proven to be correct.

Andrea Cau said...

It has to be noted that Rozhdestvensky (1975) first recognised the coelurosaurian and ornithomimosaurian affinities of Deinocheirus.

Hadiaz said...

Good stuff, Mark. I'm especially curious as to how the real thing compares to Rey's reconstruction proportionally ("In this reconstruction I extrapolated the proportions of an ornithomimid to a its giant consequences resulting in an animal somewhat similar to the therizinosaurs in bulk and shape": http://www.luisrey.ndtilda.co.uk/html/deinonew.htm ).

My only problem w/the Deinocheirus news (besides the poachers) is that it's pretty much the only SVP-related news I've heard much about in the paleoblogosphere. I've only heard about a few other SVP discoveries from the paleoblogs & only 1 or 2 per blog. Off the top of my head, I'd to hear more about the therizinosaur nesting colony, Barret/Evan's feather paper, & Archaeopteryx's tail feathers.

BTW, is Attenborough’s new programme gonna be about the NHM in general or the NHM's dinos in particular (I'm looking forward to it either way, but I'd prefer the latter).

-Hadiaz

Stu Pond said...

Great post Mark.

Mark Wildman said...

Again thanks for the comments chaps!

@ Herman - To be fair, Luis was at SVP and is thus better situated to attempt a reconstruction than many others. However, it does appear to me, and this is only my opinion and not having a go at Luis at all, quite dissimilar to what was paraded before us during the presentation.

I guess at this stage everything is open to every individuals interpretation but, as the age old saying goes, we wait for the paper. Either way, Deinocheirus is extraordinary.

I hope I will be able to plug a few gaps for you with a few posts on the various SVP presentations. Just for your info I found the data about the therizinosaur nesting colony interesting albeit nothing special, the tail feathers of Archaeopteryx are waaaaayyyyy interesting. Paul Barret's poster was interesting and I saw some of this work previously at Southampton during the Wealden Conference and I believe he makes some very important points indeed.

There are lots of extinct creatures featured in the David Attenborough programme and one or two will be named in my upcoming blog post although one or two have had to be kept under wraps. Check out the link below:

http://www.nhm.ac.uk/about-us/news/2013/november/sir-david-attenborough-reverses-extinction-just-for-one-day125985.html

Anonymous said...

@Mark

"To be fair, Luis was at SVP and is thus better situated to attempt a reconstruction than many others. However, it does appear to me, and this is only my opinion and not having a go at Luis at all, quite dissimilar to what was paraded before us during the presentation."

It's just that Rey's reconstruction is my favorite, partly b/c of how well thought-out it is & partly b/c of its "heavy metal" expression.

"Just for your info I found the data about the therizinosaur nesting colony interesting albeit nothing special,"

Just as well since, unlike the other 2 aforementioned SVP discoveries, there's at least 1 article about it AFAIK.

-Hadiaz

AnJaCo said...

Mark, my only point was that your phrasing seemed to imply that the ornithomimosaur-affinities-conclusion was dependent on the use of phylogenetics, which clearly has not been the case. "Getting me started" refers to the many bones that I have to pick with phylogentics. But I don't want to turn this into a discussion on that. Your post is much more interesting than that.

On another point, can you point to a new reconstruction of Deinocheirus that does accurately reflect the new specimens?
And has anyone hazarded a guess as to whether it may have retained any teeth? (Gastroliths do not preclude them).

Thanks.

Mark Wildman said...

That's fair enough. I was not implying that phylogenetics was the be all and end all of everything but that it merely confirmed what had earlier been ascertained by previous scientists - perhaps I could have worded it better.

All the reconstructions I have seen tend to have some of the basics correct but the hump varies in size and position and all are propotionally different. It does not help that the authors reconstruction is of a brown fuzz covered animal and everybody else's is rather gaudy.

There were no mentions of teeth at all so the jury is still out on that one - oh but for a skull to tidy things up some more.

Andrea Cau said...

I was unaware that even Ostrom (1972, fide Paul 1988) argued for an ornithomimosaur affinity for Deinocheirus.

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