Tuesday, April 2, 2013

The Plague of the Hesperonychus Meme and its Inaccuracy

That darn Hesperonychus meme again! Trust me, there are plenty more where these came from.
A random collection of pictures by various paleontologists.
I'm not normally one to criticize artwork, but I feel like something needs to be said about this. For those of you who have been keeping up with paleontological blogs (hopefully including mine) you'll remember that All Yesterdays has gotten a lot of praise for pointing out the flaws in modern paleoart, and the memes made by artists who are unfortunately copying other people's work. Darren Naish pointed out some classic memes in his presentations following the publishing of his book, which you can watch here, including the "Freaky Giraffoid Barosaurus" and the black and white Phorusrachus memes, both of which have basically become the norm for the two, but I think I found another.

Those of you who keep up with dinosaur news will remember the discovery of "America's Smallest Meat-Eating Dinosaur" Hesperonychus elizabethae (Currie 2009) (which is technically not true; that title probably belongs to one of our species of Shrike). Hesperonychus was a dromaeosaurid, or more specifically, a member of the subfamily microraptorinae and is the youngest member as well as the first to be discovered outside of Asia. This has made it of particular interest to paleontologists, and has shown that the rather primitive microraptorinae survived close to, if not until the end of the Mesozoic.

However, what is sad about this wonderful little animal is that ever since its description it has been routinely portrayed as holding its tail almost vertically in the air like a lemur (an image further made iconic by the lemur-like tail stripes on many illustrations), with what look to be relatively short arms, standing on the ground with a mostly brownish coloration. Apparently this original "look" was based on a reconstructed model of Hesperonychus following its publication, and it has since been condemned to this appearance. I know there are certainly more dinosaurs that have been condemned to far worse appearances, but I find this to be not just a pressing problem for Hesperonychus because of the "unoriginality loop" it has fallen into, but it also is being portrayed rather inaccurately.

For one, the tail of Hesperonychus has never been found. Indeed, we've only found a partial hip and a few hand bones belonging to the animal, so there is nothing suggesting that it was any different than other microraptorines. Not just that, but you don't see many other raptors holding their tails up in the air, now do you? Might be a fun idea to try, but the majority of fossil evidence currently suggests that microraptorines possessed feathered disks and fronds on their tails. Current research has shown that these tail fronds have an aerodynamic advantage (Habib & al. 2012), and are actually very similar to rhamphorhynchid pterosaur tails (Persons & Currie 2012), which is consistent with the idea that microraptorines were gliding animals. However, even terrestrial dromaeosaurids seem to have had such fronds, showing that they likely had an advantage while on the ground as well. The tails seen on the reconstructions of Hesperonychus, however, much more closely resemble those of primitive Coelurosaurs like Sinosauropteryx, and seem totally un-dromaeosaurid-like.

Given, I know that the tail has not been discovered for this animal, and thus the reconstruction can be based off the artists own personal ideas. But when the reconstruction has been drawn over and over again countless times in the same way with no creativity whatsoever, it gets very annoying. 

And the re-occuring features don't stop there. Often times Hesperonychus tends to be portrayed with what appear to be very short front limbs. This is certainly not always shown; indeed the illustration in the lower right-hand corner in the image above seems to have appropriately-sized arms based on the fossil finger bones and related species, but many of the others just seem to be way too small. The brown coloration has also become routinely shown on this creature, but dinosaur coloration has been shown to have varied widely based on our current melanosome evidence. Again, there is nothing wrong with portraying it as brown, but it's terribly unimaginative after the hundredth time.

Finally, Hesperonychus is almost never shown with the correct large flight feathers on its forearms that are seen in almost all other dromaeosaurids. This is perhaps due to the original description of the animal, as it was described by Longrich and Currie, who believed that because its size more closely matched that of the large microraptorine Sinornithosaurus millenii, it was probably flightless. Sinornithosaurus has a reduced wing, vaned symmetrical feathers, and seems to be too large to be able to glide, and this was also assumed for Hesperonychus.

This seems to be a valid argument, but as for why they decided to make their mount completely lack vaned feathers on the arm when they are still present in Sinornithosaurus does not make any sense, and has definitely contributed to the look of the animal. Also, despite Longrich and Currie's conclusion, it is still possible that Hesperonychus was a gliding animal: another dromaeosaurid, Graciliraptor lujiatunensis is in the same size range as both Sinornithosaurus and Hesperonychus, but feather impressions show that it had large, asymmetrical wing feathers and wings that approached similar proportions to the gliding Microraptor, and thus it too may have been able to glide (Martyniuk 2012). This leaves open the possibility that Hesperonychus would've been able to glide as well, and it certainly would be a nice alternative to the illustrations of walking around on the ground like some Cretaceous lemur or something....

So those are some of my thoughts about this somewhat over-used paleoart meme. Maybe if I'm up to it I'll draw a more realistic Hesperonychus with long arms, large flight feathers, and a horizontally positioned tail climbing through the branches.

Yeah, I draw. Given, I don't normally draw and I'm definitely not the best at it, but that doesn't stop me from occasionally trying. If I'm sucessful at a pic, I'll make another post to show you guys. If it was a failure, I'll never bring it up again. 'Til then, stay sharp!


Habib, M., Hall, J., Hone, D. and Chiappe, L. (2012). Aerodynamics of the tail in Microraptor and the evolution of theropod flight control." 72nd Annual Meeting of the Society of Vertebrate Paleontology, 20 October 2012.

Longrich, Nicholas R. and Currie, Philip J. A microraptorine (Dinosauria-Dromaeosauridae) from the Late Cretaceous of North America. Proceedings of the National Academy of Sciences of the United States of America, 106 (13), (2009). 5002-5007 DOI: 10.1073/pnas.0811664106

Martyniuk, Matthew P. A Field Guide to Mesozoic Birds and other Winged Dinosaurs. Vernon, New Jersey: Pan Aves. (2012) 

Persons, W. S. and Currie, P. J. (2012), Dragon Tails: Convergent Caudal Morphology in Winged Archosaurs. Acta Geologica Sinica - English Edition, 86: 1402–1412. doi: 10.1111/1755-6724.12009

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