Deinocheirus: why beer-bellies are bad-ass and the importance of being weird

Today started out as a fairly normal day. I overslept thanks to marathonning House late into the night/morning (note: not due to working late/early on my publication, oops), I dragged myself out of bed and into the office. I then, still half-asleep checked Twitter (the morning ritual was well underway) and then suddenly, I displayed both ends of the NedryGrant excitement chart (patent pending) simultaneously. Deinocheirus. It was DeinocheirusDEINO-RUDDY-CHEIRUS! At the moment, I’m in an office full of volcanologists, so no-one understood my excitement (in fact most thought I had some form of disposition, I mean I was practically frothing at the mouth with excitement). I immediately texted Richard and all my other palaeontological friends/colleagues with two words: DEINOCHEIRUS PUBLISHED.

My face on the morning of the 22nd October 2014. (I even laughed like a Dilophosaurus).

Story time

So why was I so stupidly excited? Well, I’m glad you asked. To explain this excitement, our tale begins in 1965. It was July, and the Polish-Mongolian Palaeontological Expedition had stumbled upon a ‘monster’ find. Forelimbs and a shoulder girdle 2.4 metres long belonging to a 70 million-year-old dinosaur with surely the largest forearms of a bipedal animal ever. However, that was all they found. What in the Seven Hells was this magnificent beast? Surely these the arms of some superpredator, akin to Allosaurus or perhaps a mega-Velociraptor? Deinocheirus mirificus was (‘unusual horrible hand’) was ‘born’. For seven-years, this was the most likely explanation. In this time, palaeontologists and members of the public alike went wild with fantastical recontructions of this new and wacky beast, some even going as far as noting that the arms were used much like those of a giant sloth. Alas, in 1972 John Ostrom (the guy responsible for revolutionising the way we think about dinosaurs in relation to birds in the 60s) noted that the bones in the forearm of Deinocheirus appeared similar to those found in the ornithomimosaurs, a group of secondarily-herbiverous theropod dinosaurs very similar to modern ostriches. This agreed with the sentiments of the team that initially discovered Deinocheirus, so it was settled, the beast was in fact an ornithomimosaur. Mystery solved. Right?

Dem Claws.

Dem Claws.

Unfortunately not. Fast forward a little over 40 years later to October 2013, and we still hadn’t found any more remains of the all-too mysterious Deinocheirus. That was all to change. At the SVP 2013 Symposium (one of the biggest annual events in palaeontology) there were hushed, exciting whisperings of new Deinocheirus material (apparently, I couldn’t afford to go). And then, a speaker emerged and confirmed it, Deinocheirus was back, the mystery was apparently solved. New material had been discovered and we now had a 95% complete skeleton to work with. However, this wasn’t fully shown at SVP, and the entire palaeontological community had to wait with baited breath until the work was published. One of the greatest mysteries of 20th and 21st century dinosaur palaeontology had been solved, but we had to wait. It was agonising. Personally, I grew up enthralled with the mystery of Deinocheirus as did many palaeontologists, both young and old, so to be kept in the dark like this was painful.

The Big Reveal

Fast forward again, exactly (pretty much) to a year later. Late October 2014. A dreary-eyed, 20-something-year-old palaeo grad-student is almost hyperventilating over an image he found on Twitter. Ladies and gentlemen, Deinocheirus has landed. And bloody hell if it isn’t the weirdest thing we’ve ever seen.

Deinocheirus-990x980

The Beer-Bellied weirdo in all it’s glory. Deinocheirus mirificus.

Mystery Solved

Standing almost as tall as T. rex, and weighing in at a hefty 6 tonnes Deinocheirus is the biggest ornithomimosaur to dateSo it was big, no biggie right (heh)? Wrong, in addition to it’s monstrous size it’s also (and I might have already said this) bloody weird. With a really deep lower jaw, no teeth, huge forearms, relatively small hindlimbs, a big old “beer belly” (the best description of dinosaur’s anatomy ever, thanks Tom Holtz!) and tall neural spines (similar to those seen in SpinosaurusDeinocheirus sure is different to the ‘typical’ ornithomimosaurian body plan of Galimimus, with long legs and many other features that suggested it was a fast runner. Quite the opposite, Deinocheirus was a big, sluggish brute with a huge appetite. After 50 years, the mystery of Deinocheirus seems to be solved then, it’s a incredibly odd looking, slow moving, bulky, T. rex sized, beer-bellied behemoth. Myth busted, right?

Skeletal reconstruction of Deinocheirus mirificus. Modified from Lee et al. 2014.

Skeletal reconstruction of Deinocheirus mirificus. Modified from Lee et al. 2014.

Again, wrong. These new specimens are that good that we can already begin to hypothesise how Deinocheirus actually lived out it’s seemingly odd, slow lifestyle. Deinocheirus was discovered in the Nemegt Formation, a deposit which is 70 Million years-old (Late Cretaceous), and was an ecosystem similar to that of the Okavango delta today. First off, over 1400 gastroliths were present, probably used to aid in digestion of food, (mainly plants) making up for the lack of teeth. The morphology of it’s jaws and its broad bill (similar to those found in hadrosaurs and ducks) suggest that certain muscles associated with biting were small, meaning that Deinocheirus probably ate soft (and possibly water-dwelling) plants. But there wasn’t just some stones in that big beer belly, no sir! Evidence of a half-eaten fish was found as well, indicating that Deinocheirus was no means a fussy eater, and probably a ‘megaomnivore’ eating pretty much anything it could get it could swallow. This seems to fit well, especially when you consider Deinocheirus’ place in the Nemegt ecosystem, as generalist ‘all you can eat’ type deal (finally, a dinosaur I can relate to) it wouldn’t be in such harsh competition with the other herbiverous dinosaurs in the area that mostly ate plant matter from trees. However, not only do you need to outcompete you friendly neighborhood herbivores to keep on truckin’ in a Cretaceous world, you also need to be not eaten yourself. The main threat in the Nemegt ecosystem was probably the 12 metre long, 5 ton tyrannosaur, Tarbosaurus. However, Deinocheirus seemingly has an answer to everything by sacrificing speed for bulk and size, it was probably too big (and bloody hell, those claws) for Tarbosaurus to safely take on.

Deinocheirus_fin_colcorr_lres

Deinocheirus in situ. Image credit: Andrey Atuchin.

We also know a few more tricks that Deinocheirus had up its exceedingly large sleeves. Remember those Spinosaurus-like neural spines? They were probably there to support the bulky beer belly, similar to an “asymmetrical cable-stayed bridge“. It also had broadended tip-toes (pedal unguals, to be technical), allowing it not to sink when wading into wetter areas. And those claws? No longer used as lethal disembowlers, but for digging/plant gathering. So Deinocheirus seemingly was perfectly adapted to life on the braided, meandering rivers of the Nemegt ecosystem, unafraid of pesky Tarbosaurus, perfectly content to munch away until its heart (and beer belly) was content, and then waddling to the next patch of river to devour (and P.S Deinocheirus didn’t half walk funny).

And the moral of the story is…

By now, you’ve probably found literally hundreds of grammatical and spelling errors, due to the fact that I’ve been excitedly vomiting words onto my laptop in wave after wave of dino-induced mania. Yes it’s weird, and yes I love it because it’s pretty much me in dinosaur form, but why is this important? You’ll probably see this on IFLS (I F***ing Love Science) in a summary post, with ‘weird fat dinosaur discovered’ alongside ‘cure for cancer found’ and ‘artificial intelligence finally sorted’, making palaeontology, yet again look like the stupid and childish sibling of all the other sciences (e.g. “dino with big nose discovered”, unfortunately not a joke). But this is more than just some crazy guys with beards and stetsons finding a random pile of bones and shouting eureka until Nature finally publishes their work. Oh no. This, as well as many other finds over the last year shows us just how extreme dinosaurs can get. In the past 12 months, we’ve had a new, now with more swimming (TM) Spinosaurus recontruction, Dreadnoughtus, possibly the largest dinosaur ever, as well as long-snouted and pygmy tyrannosaurs. Not to mention feathered ornithischians (R). Dinosaurs have often been regarded as evolutionary extremes, and we’re only now beginning to understand just how these extreme animals lived and evolved.This understanding allows us to further understand evolution works, and how organisms can evolve in various environments and under different conditions.Not only is Deinocheirus a weird and wonderful beast, but when we look at it as a living, breathing animal, rather than a poster-child for all things weird and wonderful, we can begin to further understand  the evolutionary processes involved in theropods, a group which would garner the evolution of an incredibly diverse and successful group of animals, the birds. Deinocheirus exemplifies that palaeontologists, by investigating extremely adapted animals, such as dinosaurs, can further the understanding of the the process of evolution, one of the most important processes on Earth, and just how far it can go, and what wonderfully strange creatures it can help to explain.

So there you have it. Deinocheirus. It sure is a good day to be a palaeontologist.

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What’s new/s 03/03/14

What’s news has been neglected a bit over the last few weeks, but fear not! Here are five exciting palaeo news stories from the last month or so:

Placoderm faces

For no particularly good reason, placoderms are a group close to my heart.  This group of fish existed during the Devonian, and are the earliest example of vertebrate with jaws in the fossil record,  As well as being generally awesome, they are also crucial to understanding how gnathostomes, the jawed vertebrates, evolved from their jawless ancestors.  Dupret et al have CT imaged a primitive placoderm, Romundina, and have shown that it has a mixture of jawless fish (‘agnathan’) and gnathostome  cranial  characters.  As with so much of evolution, the transition to attaining jaws seems to have been piecemeal, part by part, an example of mosaic evolution, with cerebral proportions remaining largely unchanged with the evolution of jaws.

Romundina

Romundina in all its glory. This is the head with front end to the left, the large, round holes are the orbits. (from phys.org)

Even more Burgess Shale

The Cambrian is famous for the weird and wonderful fossil taxa that existed during it, and the most famous Cambrian fossil site is the Burgess Shale, in the Canadian Rockies.  Since the early 20th century the incredible preservation of this site has given us an invaluable window into life 500 million years ago.  While the Burgess Shale animals were famously argued by Stephen Jay Gould to represent experimentations in body plans alien to anything alive today, more recent work has shown that actually these animals are early relatives of groups such as arthropods (ie. insects, crustaceans etc) and vertebrates (ie. you).  The other week another site was described from the Burgess Shale; hopefully this will mean we’ll see lots of new Cambrian beasties over the next few years, as well as more information on known ones,  continuing to fill in our picture of early animal evolution.

Burgessnew

A range of weird and wonderful Cambrian fossils from the new assemblage. (from Caron et al)

Aquatic Acanthostega

We already met Acanthostega, the earliest known tetrapod, a few weeks ago, when we were looking at Tiktaalik and the transition of vertebrates onto land.   Acanthostega possesses a mixture of aquatic and terrestrial qualities: like a fish, it has gills and a tail fin, but like a modern tetrapod it had digits and a ‘neck’ between the head and body.  This has been taken to demonstrate that tetrapods actually evolve many ‘adaptations to land’, such as digits, while the still lived in water, in contrast to the historical view that a (presumably rather optimistic) fish crawled onto land and only then adapted to it. Recent work by Neenan et al suggests that Acanthostega’s jaw was adapted to aquatic, rather than terrestrial, feeding, which they argue refutes recent suggestions that it might have fed on land, or at least above water.

Optimistic fish

An optimistic fish (from Pixar.wikia.com)

Playing around with flight

Imagine, if you will, a bird.  Chances are that you’re imagining something that’s probably feathered and beaked*.  The fossil record, however, shows us that many traits that we associate with birds, such as feathers and beaks, evolved before birds came into existence as a group.  Feathers are perhaps the best example, found in many dinosaurs not particularly closely related to birds, but it is also true of various skeletal characters.  Work by Mark Puttick and others shows that this is the case with the comparatively long forelimbs of birds, which originated before the origins of the group, amongst earlier dinosaurs.  Gliding dinosaurs like Microraptor suggest that many groups were independently evolutionarily ‘playing around’ with feathered gliding, it was just the birds that happened to evolve powered flight and make it through to today.

*If not, you may want to double check that you know what a bird is.

Microraptor

Microraptor: Evolutionary experimentation with flight? (from nhm.co.uk)

Primitive live birth in ichthyosaurs

As we’ve seen before on The Dinosirs, ichthyosaurs were a very successful group of Mesozoic reptiles, highly adapted to an aquatic life.  One oft quoted adaptation viviparity, or live birth, as a fully aquatic amniote can’t get back onto land to lay eggs.  This is also seen in other groups of marine reptile, such as plesiosaurs and mosasaurs.  However, a recent paper by Motani and others has suggested that actually live birth was present in ichthyosaurs’ terrestrial ancestors before they became aquatic.  They argue this based on a fossil of a very early ichthyosaur, Chaohusaurus, which appears to have been fossilised giving birth.  While this is fairly common in ichthyosaur fossils, all previous fossils have been found giving birth to babies tail first as in modern day whales, possibly as an adaptation to prevent suffocation.  This fossil demonstrates that Chaohusaurus  gave birth head first, as in most terrestrial vertebrates.  Motani et al argue that this demonstrates that ichthyosaurs evolved from terrestrial viviparous ‘head first’ ancestors, only later switching round as an adaptation to marine life as in whales today.  This is contrary to the traditional view, but does fit with our picture of modern reptiles: many groups of lizard are viviparous.

Viviparity icthyo

Chaohusaurus.: green, red and blue below are the ribs, paddle and tail of the mother respectively. Small ichthyosaur can be seen com in out headfirst in yellow. (from Motani et al)

 

References

Dupret et al (2014) A primitive placoderms sheds light on the origin of the jawed vertebrate face, Nature

Caron et al (2014) A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies, Nature communications

Neenan et al (2014) Feeding biomechanics in Acanthostega and across the fish-tetrapod transition, Proc. Roy. Soc. B

Puttick et al (2014) High rates of evolution preceded the origin of birds, Evolution

Motani et al (2014) Terrestrial origin of viviparity in Mesozoic marine reptiles indicated by Early Triassic embryonic fossils, PLOS One

Taxon of the Week: Limusaurus

As a treat, this week’s Taxon of the Week is a dinosaur. Even better, it’s a dinosaur with very small hands. Despite it’s small hands, it’s managed to cement itself amidst a pretty sizeable debate, yes ladies and and gentle, this week’s TotW is Limusaurus inextricabilis.

The facts

Limusaurus was discovered in 2009 by Xing Xu, a Chinese palaeontologist whose seemingly always discovering a new species of dinosaur (over 30 valid species to date). At around 1.7m in length (roughly the size of a large-ish dog), Limusaurus was far from the biggest and most exciting looking new dinosaur of 2009, however, it was certainly a bit weird:

  • For starters it’s the first Asian ceratosaur ever described. Yes, you heard right a ceratosaur.
  • For your main course, it’s herbiverous.
  • To finish off with dessert, it’s got a beak.
Limusurus. Not your average ceratosaur.

Limusurus. Not your average ceratosaur.

True, whilst indeed not your average ceratosaur (or for that matter, theropod) such traits aren’t that weird in primarily carniverous clades. Within Theropoda, there’s many secondarily herbiverous taxa, incl. everyone’s favourite weirdo taxon, the therizinosaurs. Let’s also not forget the well known beaked herbiverous theropods, ornithomimosaurs. Oh, and did you know crocodylomorphs had a crack at beaks and herbivory (of course they did). Even though I keep harping on about its small hands, for frak’s sake, just take a look at alvarezsaurs (with even more pathetic arms than T. rex). So why exactly am I taking the time to blog about Limusaurus?

Mononykus trying, the meme that couldn't be due to it's preposterously pathetic forelimbs. Hastily drawn by me.

Mononykus trying, the meme that couldn’t be due to it’s preposterously pathetic forelimbs. Hastily drawn by me.

A debate as simple as 1, 2, 3

If you’re a fan of dinosaurs/palaeontology then you should be aware that birds evolved from theropod dinosaurs. News flash: this isn’t new. This notion really started to gain ground after seminal work by John Ostrom in the late 1960s/early 1970s (including that famous drawing of the ‘naked Deinonychus‘ as Richard likes to call it) who noted a lot of avian-like features in Deinonychus. On top of that, palaeontological records show multiple transitional forms between smaller theropods and birds (e.g. the ever eminent Archaeopteryx), and even some of the larger theropods show avian affinities (e.g. the cranial pneumatic sinuses found in Alioramus). Those are only a select few pieces of evidence that have made the evolutionary link between birds and theropods almost undeniable, there’s a so many more, it’s astounding (incl. inferred behaviour, such as avian sleeping positions in theropods: Xu & Norell 2004, and apparent egg brooding behaviour in Oviraptor: Norell et al. 1995). Watch the video if you need more peer reviewed proof that dinosaurs (even if they did look a bit like birds) were awesome. Try and show a little respect.

However, there’s always new discoveries that just love to get people arguing. The issue revolves around digit homology/identity. Essential, theropods (via evolution) ‘lost’ two fingers (digits) to arrive at the three-fingered hand seen in most theropods (aside from the aforementioned ‘weird taxa’, who lost more than 2). The same is true for birds. However, the debate revolves around which digits are lost, and which 3 form the fingers of the hand. In tetanurans (essentially the more advanced theropods, and by extension birds), it has long been thought that digits IV and V were lost, leaving a three-fingered hand consisting of digits I, II and III. Now, you’d expect birds, by being derived tetanurans to have this digital formula.  Well that would be nice wouldn’t it. Unfortunately the question of I,II,II or II,III,IV in modern birds has been debated for a very long time. New evidence in the mid-late 1990s from developmental and genetic studies showed us that the three digits of the avian hand actually developed from digits II, III and IV. Gasp, a spanner in the works!

This new evidence was then used (rather wrongly) to attempt to oppose the hypothesis that birds evolved from dinosaurs (Feduccia 2002). While I agree, the 90s developmental evidence from modern birds creates some novel evolutionary dynamics to investigate, it cannot be used to deny the whole host of other evidence that links dinosaurs to birds. Following on from the developmental studies, genetic studies in the early 2000s showed that during the ontogeny of some birds, the digit identity would change from the initial II,III,IV to I,II,III. This led to the occurrence of the ‘Frame Shift’ hypothesis, which suggests that certain genetic pathways associated with dinosaur/avian digit identity allow for ‘rapid’ changing of digit homology throughout dinosaurian/avian evolution (at it’s core, and that’s a very simplified summary). Not to be bogged down by detail (genetics isn’t my strong suit), developmental geneticists thought they’d cracked it, and that the change in digit identity over avian/dinosaurian evolution was likely to have been caused by these frame shifts.

Feduccia's (2002) argument in a nutshell.

Feduccia’s (2002) argument in a nutshell.

Enter Limusaurus. So, finally, we come to Limusaurus’ role in all of this. In 2009, Xu et al. looked at Limusaurus’ small hands and went “you know what, that’s a reduced digit I” (NOT ACTUAL QUOTE), which makes Limusaurus’ digit identity II, III, IV. As we discovered right at the start of this article (before the I made my lack of genetics knowledge crystal clear), Limusaurus is a ceratosaur, which isn’t a tetanuran, but a more primitive theropod, meaning that the II,III,IV digit identity may well be shared by most/all tetanurans, with Limusaurus representing an intermediate of sorts. Thus Xu et al. state that the digit identity of Limusaurus is more in favour of a slower, stepwise acquisition of the digit identity seen in advanced tetanurans, and eventually birds. But, as the famous saying goes, you know what small hands means…(small gloves?)

That’s right, a big controversy.

If you're confused (don't worry, so am I), this may help.

If you’re confused (don’t worry, so am I), this may help.

The small gloves are off

The Xu et al. (2009) caused a fairly serious debate, with authors such as Vargas et al. arguing that the digit condition seen in Limusaurus is derived, and based on developmental and genetic work that they (Vargas et al.) carried out, suggest that faster genetic shifts occurred in the evolution of birds. Xu et al. quickly responded (and quoted  Arthur Conan Doyle in a somewhat dramatic conclusion) and argued that the shift proposed by Vargas is not likely when the digit (and manus) morphology of fossil tetanurans is considered.

I’d sincerely like to end this post with a succinct conclusion, saying that the debate has, over the last few years been wrapped up. However, such large debates in palaeontology, due to the very nature of our field (i.e. everything we love is dead) are rarely fully resolved. This case is no exception. Researchers from Yale (Bever et al. 2011) and other top world universities have stated time and time again that the frame shift hypothesis is still viable in the context of avian evolution, and in a recent summary by Xu and Mackem, Xu is not so sure, saying neither hypothesis has evidence to topple the other. Not one for revelling in an unnecessarily depressing ending (*coughs* Firefly) I’ll leave you with this: yes, we can’t always find all the answers to big questions in palaeontology and evolution, but by creating a synergistic relationship between palaeontology and biology (genetics, evo devo etc.), future discoveries in both fields are sure to shed some light on even the biggest of debates.

If you’d like to read more on this subject, and weren’t put off by my murdering of the genetics side of things, then I’d highly recommend the aforementioned Xu & Mackem (2013) paper for a recent summary of the field (see references below, it’s in bold).

References

Xu, X. et al. (2009). A Jurassic ceratosaur from China helps clarify avian digit homologies. Nature 459, 940-944.

Xu, X. & Mackem, S. (2013). Tracing the Evolution of Avian Wing Digits. Current Biology 23, R538–R544 (and references therein).

Bever, G., S. et al. (2011). Finding the frame shift: digit loss, developmental variability, and the origin of the avian hand. EVOLUTION & DEVELOPMENT 13:3, 269–279.

Vargas, A.O., Wagner, G.P. & Gauthier, J.A. in Nature Proceedings (2009).

Vargas, A.O. & Wagner, G.P. Frame-shifts of digit identity in bird evolution and Cyclopamine-treated wings. Evolution & Development 11, 163-169 (2009).

Young, R. L. et al. (2011). Identity of the avian wing digits: problems resolved and unsolved. Dev Dyn. 2011 May;240(5):1042-53.