Monday, 18 March 2013

Q is for Quetzalcoatlus

As there are no dinosaurs from Alberta that start with 'Q', we are going to talk about an animal that may have lived in Alberta, although there are no confirmed fossils. Quetzalcoatlus was a giant pterosaur that lived in North America during the Late Cretaceous (70-65 million years ago). Remember that pterosaurs are not dinosaurs, contrary to popular belief. The name comes from the Mesoamerican feathered serpent god Quetzalcoatl. 

Quetzalcoatlus is famous for being the largest pterosaur known from decent remains. There are two different morphs, a smaller one with a wingspan of about 6 m, and a larger one with an estimated wingspan of 10-12 m. That's about the length of a yellow bus. Can you imagine an animal with wings the size of a yellow bus?! The first fossils were found in Texas and consisted of a partial wing of the large morph, while other partial specimens from Montana have been found of the smaller morph, including partial skulls. Pterosaur fossils are extremely rare in Alberta, however, one large neck vertebra found in Dinosaur Provincial Park may be from Quetzalcoatlus based on size and some distinctive features [1]. Another partial skeleton with tooth marks and an embedded tooth from Saurornitholestes, a small theropod, is from an azhdarchid pterosaur, the group that Quetzalcoatlus belongs to [2]. Quetzalcoatlus had a large skull with a toothless pointed beak and a small crest. Like other pterodactyloid pterosaurs, it had only a short tail. 
Skeletal replica/reconstruction of Quetzalcoatlus. Photo by Liz Martin
Their fragmentary remains and strange morphology have made it difficult to fully understand this animal. Many studies have looked at whether or not Quetzalcoatlus was capable of flying, and a feature most important with respect to flight capabilities: how much did it weigh? Unfortunately, this is a very difficult question to answer. Mass estimates for the large morph have ranged from75 to 544 kg, which is a huge difference. Although 75 kg certainly would have been light enough to fly, it is not physically possible to have an animal that size weigh so little. On the other hand, 544 kg surely would have prevented the animal from flying, which begs the question - why did they have such large wings? More recent estimates have suggested a mass around 250 kg which, according to different studies, may or may not have allowed it to fly. For a more detailed explanation on the mass estimates, check out these posts by pterosaur palaeontology student Liz Martin here and here. More recently, a study has suggested that large azhdarchid pterosaurs like Quetzalcoatlus were well adapted to life on land, and moved around on land, feeding by "terrestrial-stalking", but would have been capable of taking off and flying as well [3]
Artists impression of the 'terrestrial-stalking' feeding method of Quetzalcoatlus. Image copyright of Mark Witton [3].
Although some studies have suggested that Quetzalcoatlus fed by skimming the water for fish, this idea is unlikely for several reasons. These include the fact that the fossils are found 100's of km from the nearest palaeo-coastline, and that their skulls and necks lack features required for skim-feeding, like a doubly re-inforced jaw joint found in modern skimmers [3]. In terms of flight, some studies have suggested Quetzalcoatlus was flightless, while others have shown it may have been capable of flying 1000's of km, much like a modern albatross. In this case, it would have used a short burst of energy, followed by large amounts of thermal soaring, relying on the wind and thermals to carry them. 

This is currently an exciting time for pterosaur research, and many people are looking at these animals, especially with respect to their biomechanics. There should be lots of interesting information and debates in the next few years! It is also interesting to note that Quetzalcoatlus was recently featured on a special edition Canadian quarter, the second in a series of prehistoric creatures. The image was made by a fantastic palaeo-artist Julius Csotonyi. This coin sold out rapidly, so I hope you got yours!
New 'glow-in-the-dark' special edition Canadian quarter featuring Quetzalcoatlus
Hopefully you enjoyed this post about Quetzalcoatlus, the huge pterosaur from North America. Watch for us next week when we talk about a small theropod dinosaur from Alberta!

1. Currie, P.J., and Russell, D.A. 1982. A giant pterosaur (Reptilia: Archosauria) from the Judith River (Oldman) Formation of Alberta. Canadian Journal of Earth Sciences 19: 894-897.
2. Currie, P.J., and Jacobsen, A.R. 1995. An azhdarchid pterosaur eaten by a velociraptorine theropod. Canadian Journal of Earth Sciences 32: 922-925.
3. Witton, M.P., and Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3: e2271. Freely downloadable here

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