Quetzalcoatlus

Credit: Julio Lacerda.

*Quetzalcoatlus* is an extinct genus of large azhdarchid pterosaur that lived in North America during the Late Cretaceous.

## History

The first *Quetzalcoatlus* were found in Texas from the Maastrichtian-aged Big Bend Park, Javelina Formation by Douglas A. Lawson (1971). It consisted of a partial wing, estimated from an individual 10 meters (33 feet) in wingspan. ~40 kilometers (25 miles) from the first site, Lawson found more, where he and Wann Langston Jr. (1972-1974) found three fragmented skeletons of smaller animals. Lawson (1975) announced these in a journal Science article. In the same year, he sent a letter to the same journal, making the original specimen, TMM 41450-3, the holotype of *Q. northropi*, a new genus and species; it was named after the Aztec god Quetzalcoatl and John Knudsen Northrop, who developed the Northrop planes similar in bauplan to Lawson's pterosaur. It was assumed the smaller specimens were juvenile/subadult forms of the holotype; he realized they might have been distinct species. Alexander Kellner and Langston (1996) referred them to Q. sp., since it was uncertain if they were distinct or not. These specimens include 4 partial crania at a wingspan of 5.5 meters (18 feet). In 2021, Andres, Langston Jr., Lehman, Brown, Sagebiel, Cunningham, Conway, Padian and Langston published *Q. lawsoni* as a new species to house the Big Bend *Q.* sp., after Lawson.

*Q. northropi* is considered problematic since it has yet to be properly described and diagnosed. Mark Witton et al. (2010) note the holotype is undiagnostic in every capacity, complicating azhdarchid taxonomy. Witton et al. (2010) suggest a general anatomy to be nearly identical to other large azhdarchids, overlapping some with *Hatzegopteryx*. If *Quetzalcoatlus* can be differentiated and remains valid, *Hatzegopteryx* may be considered a European variant. They also note the skull of the latter and *Q.* sp. differentiate enough to be distinct, but significance for this may not be determined since other problematic relationships exist. However, these can be resolved if *Q. northropi* is seen as valid and *Q.* sp. are investigated. Another factor is that azhdarchids were capable of long-distance flights, leading some continents to likely share and interchange genera.

BMR P2002.2, an azhdarchid neck vertebrae discovered in 2002 from the Hell Creek Formation, was accidentally recovered in a field jacket containing partial *Tyrannosaurus* remains was used for transport. Though associated with a large theropod, it shows no evidence of chewing. This pterosaur would have had a wingspan of 5-5.5 meters (16-18 feet) and was assigned *Q.* sp..

## Description

*Quetzalcoatlus* was one of the largest pterosaurs, reaching a wingspan as large as a small plane. *Quetzalcoatlus* was most likely a scavenger, eating small animals whole and eating carcasses. Unlike popular adaptations of the animal, *Quetzalcoatlus* was unable to lift or carry animals with its hindlimbs. *Quetzalcoatlus*' neck was considerably long, towering over its body and limbs. Its head bears a thin crest, which may have been coloured bright colours in life. Its eyes sat on the side of its head an had nostrils that sat high-up its rostrum. Its neck was stiffened through large muscles. It beak is very pointed, and the underside of its lower jaw bears a knob that functioned as an anchor to a soft tissue pouch in life. Old reconstructions sported a blunter beak, possibly because remains once attributed to *Quetzalcoatlus* actually belonged to a tapejarid close in form to *Tupuxuara*. The exact size of the head crest in life is unknown. *Q. lawsoni* has a wingspan of 4.5 meters, considerably smaller than *Q. nothropi*.

## Paleobiology

### Feeding

Many different ideas have been suggesting in terms of *Quetzalcoatlus*' feeding patterns. Due to the sheer vastness of the holotypes locality and the lack of bodies of water, the idea of a piscivorous diet was rejected. *Quetzalcoatlus* was then theorized to have fed like a marabou stork (an occasional scavenger, also a land-bound predator), but since its fossils have been found entangled with *Alamosaurus*, the idea was rejected. It was noted that the downturned beak of *Quetzalcoatlus* would leave a 5 centimeter, 2 inch gap when closed, a function which is unlike the hooked bills of scavenging birds. The same team proposed that the vertebrae and toothless beak were adapted to skimming.

Until 2007, the idea was challenged when another research team concluded that, for large airborne animals, skimming took too much energy to be a viable feeding method. In 2008, Mark Witton and Darren Naish noted that most azhdarchids are found in inland formations, and added on that the features present in *Quetzalcoatlus* were not compatible with other extant skimmers. They concluded that *Quetzalcoatlus* was a terrestrial-stalking hunter/scavenger. Like storks, they likely snatched small animals on land and in shallow streams. *Quetzalcoatlus* additionally has forelimb-hindlimb proportions suited towards terrestrial striding.

Witton and Naish (2015) suggest that *Quetzalcoatlus* had flexibility in the neck that allowed reach to the ground, a reclined occipital face that angled the head towards the ground, a long neck that makes easier access to the ground, increased stride in all limbs and weight bearing adaptations in the hands; these would have allowed *Quetzalcoatlus* to hunt prey with ease.

The *Quetzalcoatlus* monograph published in 2021 notes that the terrestrial ground stalking hypothesis has fared well in light of recent data. Noting that it lived in an environment with shallow bodies of water, so *Quetzalcoatlus* may have also fed there. However, Naish, suspects that the lack of terrestrial adaptations in *Quetzalcoatlus* suggest it only hunted on land.

### Flight

*Quetzalcoatlus* used its limbs to vault off of a high surface. This speed and the lift of its large wings gave the animal the ability to glide into the air. Models of *Quetzalcoatlus* have been made, and put on autopilot in a controlled simulation. They were able to fly with a combination of soaring and flapping. Though some sources have claimed *Quetzalcoatlus* to be flightless, the general consensus as of now is that *Quetzalcoatlus* would have been capable of flight as well as terrestrial stalking. *Quetzalcoatlus* was able to fly at about 130 km/h from 7-10 days at an altitude of about 4600 meters (15,000 feet). It was suggested further, by another team, that *Quetzalcoatlus* was able to fly from 13,000-19,000 kilometers (8000-12,000 miles). However, these estimates were based on relatively old size models, and *Quetzalcoatlus* differed from what they based their studies from. The newest study concludes that *Quetzalcoatlus*, and other large pterosaurs, used short bursts of speed to transition to thermal soaring.

## Paleoecology

*Quetzalcoatlus* may have stopped by in the Hell Creek formation with another unknown azhdarchid. The animal likely swooped down from the skies when it spotted small animals, or an abandoned carcass. Once *Quetzalcoatlus* was done on the ground, it would vault into the sky with its forelimbs, and quickly open its wings to take off. *Quetzacoatlus* was built for long-time flying. Though it lived in certain geographic regions, it may have occasionally landed in unfamiliar territories and surrounding rock formations.

## Notable Specimens

* TMM 4194, 4191, 42161, 42422, 41544, 42180 and 42138: Limbs, partial torso, neck and head forming a mostly complete specimen referable to *Q. lawsoni*.

## Gallery

### Fossils

Big Bend *Quetzalcoatlus* remains sitting in the Texas Vertebrate Paleontology Collection.Big Bend *Quetzalcoatlus* remains sitting in the Texas Vertebrate Paleontology Collection.Big Bend *Quetzalcoatlus* remains sitting in the Texas Vertebrate Paleontology Collection.*Quetzalcoatlus* cervical vertebrae.*Quetzalcoatlus* cervical vertebrae.*Quetzalcoatlus* cervical vertebrae.*Quetzalcoatlus* cervical vertebrae.A *Quetzalcoatlus* cervical (top), femur (middle) and finger digit (bottom).*Q, lawsoni* claw at the National Park Service inventory.
### Diagrams

The large individual is *Q. northropi*, B and C are *Q. lawsoni* and D is *Wellnhopterus*.Speculative launch positions.Speculative launch positions.
## References

* https://en.wikipedia.org/wiki/Quetzalcoatlus
* https://en.wikipedia.org/wiki/Javelinadactylus
* https://doi.org/10.1007/s11756-021-00841-7
* https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1907587
* https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1780247
* https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1593184
* https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1780599
* https://tetzoo.com/blog/2021/12/8/the-quetz-monograph-lives
* https://phys.org/news/2021-12-fleshing-bones-quetzalcoatlus-earth-largest.html