Have you ever seen a pterosaur taller than a giraffe?

In the Mesozoic exhibition hall of the Houston Museum of Natural History, fossils of reptiles from ancient times are lined up in a spectacular manner. Among the group of dinosaurs, there are two strange figures: their long necks are bony, their sharp beaks are cold, their hollow eyes look down upon everything, and they look very eerie with the blue-green lighting of the exhibition area. They are the Quetzalcoatlus, one of the largest pterosaurs in the history of the earth.

Quetzalcoatlus skeleton at the Houston Museum of Natural History | Daderot / Wikimedia Commons

Take off in the name of Quetzalcoatl

In the summer of 1971, in Big Bend National Park on the border between Texas and Mexico, an American boy was hiking in the deserted wilderness. He was Douglas Lawson, a graduate student majoring in geology at the University of Texas, and he was struggling with his graduation thesis.

Luck favored this diligent young man, and he soon discovered an exposed pterosaur finger bone fossil in the rubble. Lawson immediately called his teacher, Professor Vaughan Langston, who rushed over upon hearing the news and quickly organized a team to conduct an excavation survey. As the surrounding rock was gradually cleared, a surprisingly large pterosaur wing fossil gradually appeared in front of the researchers. Conservative estimates suggest that the wingspan of this pterosaur could reach 10 meters, which is almost as big as a small fighter jet.

Field Museum model of Quetzalcoatlus | Eden, Janine and Jim / Wikimedia Commons

The stratum excavated this time belongs to the Javelina Formation, which is an important fossil producing area in North America. Unlike the desolate Texas wilderness today, this place was a paradise where dragons and birds sang together. So far, a large number of dinosaur fossils have been discovered, including Alamosaurus, Bravoceratops, Minisaurus, Sauroraptor and Tyrannosaurus Rex. It is a veritable Cretaceous dinosaur park.

The teacher and student soon published this important discovery in the journal Science. When naming this giant sky monster, Langston felt that he had to use a domineering name to match such a giant beast. He suddenly had an idea and thought of the highest god commonly believed in Mesoamerican civilization - Quetzalcoatl.

Quetzalcoatlus skeleton | Kenneth Lu / Wikimedia Commons

The belief in Quetzalcoatl was popular in the Olmec, Aztec and Mayan civilizations. The image of Quetzalcoatl in ancient murals was a snake with bird feathers. According to legend, Quetzalcoatl was in charge of harvest and rainfall, stars and astronomy, and was one of the most important gods in the Yucatan Peninsula. Naming this giant pterosaur after a god shows how much scientists marveled at its size, and in Chinese it is usually translated as the wind god pterosaur.

Slim and tall

Because the bones of giant pterosaurs are extremely fragile and difficult to preserve, complete fossil specimens are often difficult to preserve. Therefore, when paleontologists speculate on the size of large pterosaurs, they can only estimate the size based on the proportion of the species with more fossils and apply it to the incomplete pterosaur finger bones. Due to different calculation methods, the data may be biased. Initially, beginners estimated that the wingspan of Quetzalcoatlus could reach 15.5 meters, but the latest research shows that it was actually only about 10 to 12 meters. Scientists later discovered another unnamed Quetzalcoatlus in Montana, with a wingspan of only 5 meters.

Size comparison of Quetzalcoatlus. The larger one is Quetzalcoatlus northropi, and the smaller one is another species that has not yet been named | Matt Martyniuk (Dinoguy2) / Wikimedia Commons

The weight of Quetzalcoatlus is a mystery that has been debated by paleontologists for many years. Based on the super-large wingspan of Quetzalcoatlus, American aviation experts estimated that its weight was only about 100 kilograms. But soon someone raised an objection: with such a large body and a weight of only 100 kilograms, it would be difficult for it to stand, let alone fly. Another scholar estimated that the weight of Quetzalcoatlus was about 544 kilograms, but this was also denied by everyone: such a "fat" pterosaur, even if its muscles were strong, it could not overcome gravity. Today, the mainstream view is that the weight of Quetzalcoatlus was between 180 and 250 kilograms.

The height of Quetzalcoatus is close to that of a giraffe, but a giraffe with a "devilish figure" weighs more than 1 ton. What secret did Quetzalcoatus, which is of similar height, keep its body slim? The answer lies in its bones. The bones of Quetzalcoatus are hollow, with extremely thin bone beams, forming a lightweight honeycomb structure. This structure can not only greatly reduce weight, but also improve the toughness and strength of bones.

Flying Bully

The forelimbs of Quetzalcoatlus are covered with strong muscles, which account for a quarter of its body weight. The well-developed muscle groups give Quetzalcoatlus strong forelimbs, and the powerful wings can help them support their bodies and walk on land. When taking off, they will use their forelimbs and hind limbs to push themselves up to the sky with the reaction force of the ground, and then spread their wings to fly into the sky.

In the past, people often thought that the wing membrane of pterosaurs was just a thin layer of skin, but according to the analysis of wing membrane fossils, its structure is actually very tough. The wing membrane has a cuticle layer on the top and bottom, and rich blood vessels and strong muscle fibers in the middle. It is not only strong but also very elastic. Such strong wings can allow pterosaurs to withstand wind and rain and will not be easily scratched.

An artist's impression of the soft tissue of a pterosaur wing. The multiple layers make up the solid tissue | Sankar Chatterjee & RJ Templin / Special Paper of the Geological Society of America (2004)

Scientists speculate that Quetzalcoatlus flew in a similar way to today's albatrosses or vultures, because they all have exaggeratedly large wings. These heavier fliers are good at using rising hot air to stay in the air for a long time without flapping their wings. This flying style is called "soaring." Quetzalcoatlus also has the ability to flap its wings, but using the power of thermals can effectively save energy.

Comparison of wing shape between pterosaurs, albatrosses and condors | Mark Paul Witton & Darren Naish / PLoS ONE (2008)

The skull of Quetzalcoatlus is about 2.5 meters long, with no teeth in its mouth, and sharp jaws covered with a hard keratin layer. This often underestimated deadly weapon is called the terrifying "death beak" by scientists.

When Quetzalcoatlus was first discovered, scholars believed that its long beak was used for fishing. However, the fossils of pterosaurs that usually catch fish are found in marine strata, but Quetzalcoatlus was unconventional and lived in inland plains, buried with terrestrial dinosaurs. So what was the function of Quetzalcoatlus' beak?

Scientists speculate that when Quetzalcoatlus twisted its neck and swung its beak, it was enough to pierce the skin and flesh of the dinosaurs. Quetzalcoatlus might hover in the air to search for animal carcasses, and once it found its target, it would land and use its huge size to drive away other predators and enjoy a feast. If there were no carcasses, Quetzalcoatlus might also attack small dinosaurs on land, and would not let go of the dinosaur eggs in the dinosaur nests.

A savage Quetzalcoatlus attacks a baby dinosaur | Mark Witton and Darren Naish / Wikimedia Commons

But hunters also have their moments of failure. A Quetzinus pterosaur found in Canada had a tooth of the Saurornithine deeply embedded in its finger bone. Although it is not certain whether the Saurornithine ate the corpse of the Quetzinus pterosaur, it is conceivable that the overlord of the sky had to bow to the fierce theropod dinosaurs when he came to land.

A prosperous family

Quetzalcoatlus was not alone in the skies of the Late Cretaceous. Since the 1980s, scientists have discovered a variety of giant pterosaurs, including Acheron, Bauconi, and Hatzegopteryx. They and Quetzalcoatlus all belong to the family of the Mysopterygidae. Hatzegopteryx, discovered in Romania, has a wingspan of more than 11 meters. It is larger and stronger than Quetzalcoatlus and has become the largest flying animal.

Estimated size and skeletons of giant pterosaurs. A and B are Hatzegopteryx, C is Arambourgiania philadelphiae, of which only a few skeletons have been found, and the size is unknown; D and E are small Quetzalcoatlus, which has not yet been named | Mark Witton / Wikimedia Commons

The Mysopterygidae is a relatively late pterosaur family, which just appeared on the historical stage in the Early Cretaceous period 108 million years ago. But in just a few million years, they grew rapidly in size and became the absolute rulers of the Cretaceous sky. The Mysopterygidae are all large pterosaurs, and even the smaller ones have a wingspan of 3 to 4 meters. They have slender necks and long toothless beaks, and are a kind of ferocious predators. Fossils show that Hatzegopteryx is the top predator on the European islands, making the pterosaur family climb to the position of "overlord" unprecedentedly. They fell from the sky, catching the dinosaurs on the islands off guard, and after landing, they started a killing spree and could not be stopped.

Reconstruction of Quetzalcoatlus | René Kastner / Wikimedia Commons

The pterosaurs were widely distributed in North America, Europe, Africa and Asia during the Cretaceous. It is worth mentioning that Zhejiang Pterosaur, which belongs to the family of the pterosaurs, was discovered in Linhai City, Zhejiang Province. It is not only the first fossil of the pterosaur family found in China, but also the most complete fossil specimen of the pterosaur family known.

At the end of the Cretaceous period, an asteroid hit the Earth, causing all pterosaurs, including Quetzinus, to disappear along with the dinosaurs. The huge size meant higher energy consumption, and the size that Quetzinus was proud of now became a fatal flaw. They could only sit and watch as the small flying animals around them gradually eliminated them. The pterosaur family dominated the vast sky for billions of years, but eventually gave way to the rise of birds.