Quetzalcoatlus

Quetzalocatlus northropi is a giant azhdarchid pterosaur from the Maastrichtian Stage of the late Cretaceous. The species is the only known species of Quetzalocatlus, though some consider Hatzegopteryx thambema to belong to the same genus as Quetzalocatlus.

Quetzalcoatlus is known from the middle to late parts of the Maastrichtian stage (68 to 66 million years ago) and lived in Laramidia, which is now the western part of North America. It is widely considered to be the largest pterosaur by the general public, though Hatzegopteryx grew to at least the same proportions.

PICTURE: Shows a trio of Quetzalocatlus hunting on the ground for small animals, in line with the most recent scientific theories.

Discovery, Fossil Record & Species
In 1971, the first remains of Quetzalocatlus were discovered in Texas in the Javelina Formation. The remains consisted of a partial wing that was estimated to belong to an animal with a wingspan surpassing 10 meters. In the following years, the remains of three much smaller individuals were discovered, and in 1975 the finding of the new giant pterosaurs were described in the journal Science and given the name Quetzalocatlus in honour of the Aztec feathered serpent god Quetzacoatl.

In 1996, paleontologists Kellner and Langston considered the three smaller individuals to belong to a different species, though they hesitated to give the species a name because of its uncertain position.

In 2010 Mark Witton et al. pointed out that though in many cases the remains of Quetzalcoatlus northropi and Hatzegopteryx thambema are indistinguishable, the skull material of the latter differs from Quetzalcoatlus northropi. It is very likely that huge, flight-capable animals would have had intercontinental ranges, such as many much smaller birds, making the presence of a single giant pterosaur on many continents unsurprising.

Part of the problem is that the holotype specimen of Q. northropi is yet to be properly described beyond a short article, so most comparisons have to rely on the smaller specimens.

The only other remains of Q. northropi were found in 2002 in the Hell Creek Formation (see here for more about Hell Creek) next to the remains of a Tyrannosaurus, though this was represented by only a single neck vertebra. The bone shows no sign of damage, and it is possible that it was the Quetzalocatlus that was scavenging on the dead tyrannosaurid, not the other way around.

Distribution
Quetzalocatlus remains have several times been associated with the semi-arid inland plains that were found in the center and southern parts of Laramidia, in the same area as the contemporary sauropod Alamosaurus. It might also have been prevalent further to the east and west, as the Hell Creek Formation remains suggest.

All remains of Q. northropi have been dated to around 68-66 million years ago.

Paleobiology
The diet of Quetzalcoatlus and other azhdarchid pterosaurs in general has been the subject of many theories. In 1975 in the original article that described the first four specimens, Lawson noted that it did not live in proximity to seas and thus was not a fish eater. Lawson speculated that the azhdarchid might have instead fed upon carcasses, especially those of the giant sauropod Alamosaurus. In 1996, Lehman and Langston rejected the theory, instead claiming that Quetzalocatlus northropi had a beak structure very unlike that of modern scavenging birds, and thus was unlikely to have scavenged as a primary source of its food. They postulated that, despite the distance of the remains from the ocean, Quetzalocatlus northropi was primarily a fish eater.

A 2007 study argued against the fish-eating hypothesis, which had then become the leading theory for the diet of giant azhdarchid pterosaurs like Quetzalocatlus and Hatzegopteryx, because it was not energy efficient enough to support such a  large animal because of the massive drag resulting from even dipping a beak while flying into the water. Soon afterwards, in 2008, Mark Witton and Darren Naish published a detailed study on the feeding habitats of azhdarchid pterosaurs, pointing out how many azhdarchids lived far away from seas and how they were better-adapted for walking on all fours (with the wings as a second pair of legs) than other pterosaurs, and concluded that they were terrestrial stalkers like modern storks. Of course, they would still have flown, but they could have hunted on land for small animals.

This theory has since been widely accepted and is now considered to be an accurate representation of the lifestyle of azhdarchids in general.