Monday, June 2, 2014

Was Deinocheirus the Largest Waterfowl of All Time?

*From June 2 before the recently published material Lee et al. 2014, but I may have got pretty close in my prediction!! October 22, 2014

Just when you thought the giant armed, saddle humped, therizinosaur mimicking Deinocheirus could not get any weirder with the reveal of the skull the fossil record throws up a proverbial hail mary that shows us all what a crackpot evolution can be. It has, for all intents and purposes, a duckbill.

Nestled somewhere between an ostrich and a duck, this new skull recently repatriated to Mongolia but currently unpublished, is sure to stir up quite a bit of speculation regarding the lifestyle of this perplexing chimera that has haunted the minds of dinosaur lovers for decades now. So let me add my antediluvian salad take on how this Mesozoic mash-up may have lived.

(c) Andrey Atuchin.
So far this depiction (used with permission) of Deinocheirus by Andrey Atuchin is my favorite so far. What strikes me is how real the Deinocheirus  looks - not some bizarre amalgamation of different animals like many other renderings depict. What I also noticed was the environmental context the animal was put in - a wetland setting. Now I had always  thought of the Nemegt as sort of a wetter desert and many depictions of it suggest such a mosaic of sand dunes with some forest cover. Turns out I was only partially right.  The Nemegt was an endorheic basin - water flowed into the system but not out. Even in very arid climates such a confluence of watershed and topography can create very lush habitats. A good modern proxy may be the Okavango Delta of Botswana which is seasonally flooded and replete with all the classic megafauna of Africa but otherwise in an arid climate.

Okavango Delta. Botswana. wiki
Now with this wetland environment and duckbill head in mind, it begs the question: was Deinocheirus a dabbler? Obviously the skull needs to be worked upon, finite element analysis performed etc etc. And let us not get carried away by the shape of the skull because we all know what happened with the supposedly "semi-aquatic, dabbling" duck bill dinosaurs... But are we looking at the largest waterfowl of all time?

Magpie Goose. wiki
We don't tend to equate large size with making a living as a dabbler of aquatic vegetation. In modern ecosystems this niche is primarily occupied by birds of the order Anseriformes - your ducks, geese, swans etc etc - which as a group were just coming into their own in the Cretaceous but doubtless not as diverse or abundant as they are today. And of course we do not have multi ton waterbirds or dabblers of any sort in this size range. Does this imply such a lifestyle could not have provided for a huge dabbler in the past? I say: why not? Consider the size of migratory flocks of waterfowl. The stories of how huge flocks of ducks and geese blocked out the sun is stuff of legend and lore in the not to distant past in America. And if you start to look at the huge amount of biomass that flocking waterfowl represent and start to look at them not so much as individuals but as a giant super-organism it starts to become more and more negotiable in imagining dabblers on dinosaurian size scales. However unlike the situation today where a temperate, seasonal climate necessitates migration of waterfowl flocks to find adequate food - the more equatable, balmy climes of the Mesozoic may have offered more opportunity for dabblers to exist in one area permanently.

(c) Gerry Dewaghe
And if we start to consider the possibility Deinocheirus acting as a mega-dabbler we should also start to explore what food stuffs it was targeting. The roots, bulbs, and tubers of emergent vegetation are nutritious/starchy foodstuffs and often consumed by aquatic birds. The big clawed hands of Deinocheirus may have even assisted with such endeavors. Suspended organic matter in the water, small aquatic organisms offer another avenue of dietary choice. But if I could suggest one food item in particular that could offer sustenance for a huge dabbler on the scale of Deinocheirus it would be the aquatic fern Azolla.

Azolla. Duane Nash
Now I have talked about Azolla before here but what you should know is that this floating, aquatic mat forming fern is a bit of a super-plant. It spreads wildly, growing fast, assisted by N-fixing bacteria it can colonize waters devoid of nutrients. It is relatively nutritious with good levels of protein, vitamins, minerals, essential fatty acids and has received attention as a food crop for domestic animals. Although we do have good records of Azolla going back pretty early in the Cretaceous I can not find any reference to Azolla in the Nemegt (but reference to the paleoflora of the Nemegt is sparse anyways). There is evidence for Azolla in India and North America more or less bookending the Nemegt between the two land masses and given how well aquatic plants spread and disperse it would not be surprising for Azolla to be part of the flora of the Nemegt. And if you had acres upon acres of flooded landscape, in a landscape without the grasses and papyrus that dominate the Okavango, Azolla seems like a good candidate for such an environment creating huge amounts of biomass supporting Deinocheirus, and probably other, dinosaurs.

Azolla filculoides. wiki

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strangetruther said...

Hi! Yup - maybe it was.

Your Magpie Goose pic has some sparkly artifacts particularly round the head area. Even the enlarged version has this a bit. This can be minimised by slightly blurring photos before reducing them in size.

BrianL said...

Is it me or are those ornithomimosaurs (including Big D.) naked or only very very sparsely covered in fuzz?

As for *Deinocheirus* being a 'dabbler', I'm not sold on that though mostly for practical reasons. How big would their oasis or 'oasis' have to be to support a yearlong population of these beasts? Also, taking Mesozoic balminess into consideration, one would expect there to have been other creatures like this around during so long a time period, wouldn't we? This is negative evidence, but we simply do not know of any 'dabblers' this size, much less non-volant ones.
If we just look at size and anatomy, surely large and broadmouthed hadrosaurs and the likes of *Nigersaurus* are the best analogy around for *Deinocheirus*?
That being said, I do enjoy your out of the box thinking as usual. Would you happen to have an explanation for why all these huge coelurosaurs (except giant tyrannosauroids) are exclusively Asian?

Duane Nash said...

Thanks for comments.

@strangetruther (nice name) I don't know I just stole the pic off of wikipedia it looks fine to me...

@BrianL The idea of giant multi ton wading fisheaters in the Mesozoic has largely been accepted - spinosaurids. There are no multi-ton wading predators around today or even anything approaching that size. Why could there not have been multi-ton dabblers around in the Mesozoic as well? If you look at the sheer biomass of huge flocks of dabbling waterfowl around today I think it opens the door to thinking about large dabblers if the conditions allowed. I suggest Azolla aquatic fern as a potential food supporting such animals.

As for the seeming lack of other dabblers maybe we need to consider the possibility that we are misinterpreting them. You mentioned Nigersaurus and broad-mouthed duckbills, maybe they were grazers but did a bit of dabbling as well? ... like many geese/ducks do both grazing and aquatic foraging/dabbling. I remember a paper a while back suggest some ornithomimids had keratinous lamellae indicating potential dabbling. Maybe some slack jawed weak toothed ankylosaurs slurped up algae/aquatic plants on the regular? My point is there may in fact be more - we are just not seeing them because we are looking through the lens of modern ecosystems where all large animals are well behaved mammalian herbivores. And dabblers are relatively smaller.

And in the case of the Nemegt in the post I went over the environment which closely approximates it- the Okavango delta- a seasonally flooded inland basin with no outflow. Perfect for a dabbler. I should stipulate that dabbling need not exclude other methods of foraging for terrestrial plants, fruit, bulbs, etc etc.

But we still have to wait and see what the skull publication tells us. Are there any signs of lamellae, was the bite powerful or weak?

BK said...

I remember suggetsing this, getting a lot of hate for not thinking it a herbivore then being proven right with the fish remains....

Anonymous said...

Bk Jeong, I wonder if it also scavenged on dead animals similar to a vulture with a serrated tongue and roof teeth.

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