Posts Tagged 'theropod'

Gobivenator

So the near endless procession of incredible and incredibly preserved dinosaurs from the Cretaceous of Mongolia continues. This time it’s a troodontid, newly named Gobivenator mongoliensis by Taka Tsuihiji and colleagues in Naturwissenschaften. Although the paper concentrates on the issues of palatal evolution (alongside a short description), the thing for me is just how exquisite the specimen is. It’s one of the best preserved things I’ve seen from Mongolia, and given things like the fighting dinosaurs, nesting oviraptorosaurs and the rest, that’s saying something.

I have actually seen this specimen firsthand while visiting Japan back in 2011 and it really is superb. Also worth nothing is the quality of the preparation – although at one level it’s quite easy, a nice fine and fragile sandstone with strong and well-preserved bones – the delicate nature of the specimen (especially an intact skull with all the palate, braincase etc. intact and in situ) is something you don’t want to damage. Handling the material to take photographs was fraught with panic trying to avoid damaging anything.

And on that note, yes there are photos. Taka has generously said he’d let me publish a few of mine online, and show some non-standard views. However, he is planning a monograph on this (and so he should!) so he asked I not reveal too much, so I’ve stuck to a general shot of the prepared pieces, back by a shot of the tail (so nearly complete and yet not quite, curses!) and a shot of the dorsal ribs. Nothing too incredible, but whether or not you’ve seen the paper, I think this gives a better impression as to the sheer quality of the preservation and the state of the material, it really is a beauty.

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Another incredible Gorgosaurus

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Gorgosaurus has had a lot of love on here thanks to the huge series of posts on the preparation of a specimen by Darren Tanke, but also with this recent effort. Despite the awesome quality of those, this one is arguably better. While not complete (almost no tail dang it) and with a little bit of squishing to the skull, this one clearly retains an awful lot of the 3D relationships between bones and it overall rather uncrushed. This is a rarity to say the least and really helps show just how, well, big these things were. As you can see from the images, the animal is really barrel-chested and chunky. Obviously restoring muscles and fat layers etc. is another issue entirely, but I think it’s fair to say that this animal should really not be slim.

Obviously there’s a ton of just beautiful detail here and some lovely nuances (like the interlocking gastralia, the massively retracted left leg, the ilia tight to the neural spines of the sacrum, and the rugosities on the snout). It may not have quite the visual impact of the last one, but there’s really a lot to be gained from this and palaeoartists out there should be (t0 quote a friend of mine) onto this like a starving chihuahua on a pork chop.

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The giant, feathered tyrannosaur Yutyrannus huali

So perhaps inevitably the fossil beds of Liaoning in China have coughed up yet another fascinating feathered dinosaur. Yutyrannus huali (which translates as the ‘beautiful feathered tyrant’) is big – as big as some of the Late Cretaceous tyrannosaurines with the largest specimen being around 9 m long and estimated to have weighted close to 1.5 tons. In short, this was big. And feathered. While they are not brilliantly preserved, they are clearly present in places and directly associated with the skeleton as should be expected.

There are a few interesting things about this and I’ll go over them in turn, though as ever the first port of call should really be the paper for the real nitty gritty. First off, the specimens themselves – there are three of them, so this is already a well known animal, and two are basically complete. There’s a lot of anatomy right there and yes, I have to confess, rather more than some other tyrannosaurs I could mention. Indeed two of them are preserved together, as a pair, which nicely hints at least (well, I’m going to say so) at the possibility of sociality (theropods being more social than previously suggested, how interesting?).  Multiple specimens are always great and animals this size being preserved at all are quite rare in the Jehol, so it’s pretty impressive we have three of them. They are also preserved in that psuedo-3D manner I mentioned the other day so there’s really quite a bit of detail there and they are not badly crushed or mashed (as you can see in the pictures below).

Now it is of course already known that tyrannosaurs were feathered, with the basal Dilong being preserved with feathers. The question is of course, did the bigger ones like T. rex have them? There’s been suggestions that they didn’t as they could overheat and there are hints of scaly, feather-less skin from impressions refereed to Tyrannosaurus. So while at least some tyrannosaurs certainly had feathers, and large ones certainly could have done, this is definitive evidence that they genuinely did. The size issue is of course interesting since indeed, very large animals tend to reduce insulation to avoid overheating (elephants, rhinos, hippos etc. are not that hairy and indeed elephants can struggle to keep cool). The obvious exception being animals that live(d) in cold climates like mammoths, and the researchers note that actually the environment Yutyrannus lived in was likely rather cooler on average than that occupied by a number of later tyrannosaurs, so this may indeed have helped them stay warm.

Below are some pictures of the various fossils. While you’ve probably seen a number of these before on all the other sides my insider contacts means I’ve been sent a few to use which were neither in the paper nor press release. So there’s something novel here for everyone, even if it’s not in the text.

Top image by Brian Choo (used with permission) and the rest courtesy of Xu Xing and colleagues.

Xu, X. et al. 2012. A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature. doi:10.1038/nature10906

An articulated alvarezsaur pes

Some well-know and well studied taxa can often have little bits consistently missing from their fossils and it can take many years before every part of their anatomy is known. In the case of the derived alvarezsaurs it was only very recently that a complete pes was known with the discovery of Albinykus. This was rather unfortunate for me, as it somewhat renders much of my new paper redundant.

Yes a couple of years ago while out prospecting at Bayan Mandahu I came across this delightful little alvarezsaur pes. What is nice about it though is that it has digit I intact, something unknown in the clade (well, when I found it and started work describing it). The piece was actually found within a good stones throw of the points where both Linheraptor and Linhenykus were found, so that’s clearly a good spot to be working in. In this case we refer the pes to Linhenykus given the similarity in form and that it was found in the same locality, and perhaps even the same horizon since both the holotype and this specimen were preserved in nodules.

Linhenykus pes from Hone et al. 2012. Scale bar is 10 mm

So much so not especially interesting perhaps, having been beaten to the punch. True, but we were able to expand our discussion a little in looking at the shape and structure of the metatarsus. Alvarezsaurs like a number of derived theropod groups have a ‘pinched’ metatarsal III resulting in the arctometatarsalian condition. The evolution, structure and function of this set-up has been discussed at some length in a variety of papers, but we were able to provide some extra little details which seem not to have been looked at previously.

While it recognised that despite the proximal and posterior constriction, some metatarsal IIIs have a mediolateral expansion – in other words, looking at the front of the element, it can look quite fat a way up the shaft. Our examination of this and subsequently other specimens suggests that this is a thin flange of bone that sits on top of mts II and IV. This doesn’t seem to have been mentioned before (and I was pleased to see that the referees, both of whom have looked at this extensively, agreed with this assessment) and is potentially quite odd. The structure of the arctometatarsus seems linked to running efficiency and reducing motion between elements. However, having a flange of bone here on the anterior face would presumably help stop mts II and IV moving forwards relative to III, or III posteriorly relative to the others, or even both. Only this seems a rather unlikely problem for even a highly cursorial animal. This is clearly beyond the scope of a short descriptive paper to deal with, but it is (I think) an interesting observation.

Related to this, the exact shape and structure of mt III in this specimen compared to the holotype of Linhenykus is a little different. One might expect such a derived and specialised condition to be highly conservative which suggests the selection is potentially quite weak on this specific structure. It also hints that there may be more variables and details to the arctometatarsus than previous realised.

As a final little note, this paper is out in Acta Palaeontologica Polonica so is freely accessible, though currently as a horrible uncorrected proof, as indeed is the long and detailed description of Linhenykus that follows last year’s brief work in PNAS.

Hone, D.W.E., Choiniere, J.N., Tan, Q. & Xu, X. An articulated pes from a small parvicursorine alvarezsaroid (Dinosauria: Theropoda) from Inner Mongolia, China. Acta Palaeontologica Polonica, in press.
Xu, X., Upchurch, P., Ma, Q., Pittman, M., Choiniere, J., Sullivan, C., Hone, D.W.E., Tan, Q., Tan, L., Xiao, D., & Han, F. Osteology of the alvarezsauroid Linhenykus monodactylus from the Upper Cretaceous Wulansuhai Formation of Inner Mongolia, China, and comments on alvarezsauroid biogeography. Acta Palaeontologica Polonica, in press.

Ceratosaurus and Dryosaurus

I’m not quite out of Canegie photos yet, so here are the mounted Ceratosaurus and Dryosaurus. My first of either and while it is cool to see a young Ceratosaurus (I simply didn’t know there were specimens of animals this size) I must confess I had hoped to see an adult Allosaurus-sized individual. Still these are both classic Morrison taxa and added still more to my ‘first time’ list of species that I got from this trip to the U.S.

Rex heads

Following my last few posts clearing out my archive of photos of theropod skulls here’s a couple of Tyrannosaurus heads in near ventral view. The upper one is from Oxford and has, I think, a nice background in the glass roof panels, while the lower image is from the IVPP in Beijing.

Deinonychus

Hardly festive, but definitely awesome. A pair of mounted Deinonychus skulls from museums in China (above) and Japan (below).

Last Allosaurus, promise

Well, I’m on a roll, so here’s some photos of a cast of an Allosaurus skull held in Japan.

Another other Allosaurus

I’ve had this photo knocking around for a couple of years and never got around to using it. It’s an Allosaurus skull cast on display at the BSPG in Munich. However, with my recent post on the Carnegie Allosaurus, it seemed a good time to drag this out of the vaults and stick it on show. That’s it for today.

Allosaurus


Ah Allosaurus, probably the dinosaur with the greatest discrepancy between how good the same sounds and what it actually means. Rather a disappointment on that front really isn’t it old chap? Still, I’ve got some decent photos and it’s been a good while since Al has anything like a look in on here despite his iconic status as a ‘classic’ dinosaur, so here he is.

 

Guest Post: Love the Tyrant, Not the Hype

Tom and, shock!, *not* Tyrannosaurus....

Today Tom Holtz brings his piece to the table. Well, I say piece, Tom has promised me three (though he also originally promised to do a guest post about 2 1/2 years ago…) and this is a pretty big first one. Although he’s not a blogger, Tom is renowned for spending a lot of time online and handling questions from the public and getting involved in debates, so he’s very active on the outreach side of things. His recent dinosaur book featuring Luis Rey’s art really is an instant classic (and Tom maintains a great online species list for this). Anyone who knows Tom’s work knows about his fondness and affiliation for tyrannosaurs, so having just covered this little critter, it’s great timing for him to dive into tyrannosaurs for us:

Continue reading ‘Guest Post: Love the Tyrant, Not the Hype’

Oh so pretty

At least a few readers should have seen this by now. It’s a new theropod fossil from the Solnhofen of Germany and inevitably features some champion UV work by Helmut Tischlinger (who provided these photos). It’s odd to be putting this up when the paper describing this critter is not even out yet, but these photos are on a number of blogs and all over the German press so I don’t feel that I’m really doing the authors a disservice (and indeed I have permission to post them). So enjoy the beauty of this animal and keep a look out for the publication.


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