An Ultimate Guide to Tropeognathus: The Keel-Jaw

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Name Meaning“Keel Jaw”Height7 to 8 meters in wingspan (23 to 26 feet)
PronunciationTROH-pee-ohg-NAH-thusLength4 to 5 meters (13 to 16 feet)
EraMesozoicLate CretaceousWeight100 to 200 kilograms (220 to 440 pounds)
ClassificationPterosauria, Pterodactyloidea & OrnithocheiraeLocationBrazil, England, and North America.

Tropeognathus Pictures

Tropeognathus | Racksuz via GettyImages

The Tropeognathus

Gage Beasley Prehistoric's Tropeognathus Concept
Gage Beasley Prehistoric’s Tropeognathus Concept

Tropeognathus was a large flying reptile that lived from the Early to Middle Cretaceous Period, between 125 and 100 million years ago.

It lived in South America and is considered one of the largest pterosaurs known to have lived in the Southern Hemisphere. 

Fossils of the Tropeognathus were first discovered in the early 1980s when they were acquired by a German museum from Brazilian fossil dealers. 

The exact provenance of the fairly complete skull fossil isn’t known, but it was probably recovered from rocks of the Santana Formation in Cerra, Brazil. Tropeognathus was named and described officially in 1987 by Peter Wellnhofer.

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

The pterosaur’s name is of Greek origin, meaning “keel jaw,” referring to the bony keel at the tips of its upper and lower jaw. 

Tropeognathus was a colossal beast, but it lived off a diet of fish and other aquatic prey. 

The identity of this pterosaur was muddled up in the early years after its discovery but was later clarified as additional fossils were discovered in the 21st century. 

This article will cover some of the most fascinating details about the Tropeognathus, including where it lived, how it lived, and its significance to science.

Physical Characteristics

Restoration of three flying individuals
Restoration of three flying individuals | Dmitry Bogdanov via Wikipedia (CC BY 3.0)

Tropeognathus was a relatively large pterosaur

In fact, it is arguably the largest pterosaur known from Gondwana, the landmass formed by the amalgamation of the southern continents. 

It also rivaled some of the largest pterosaurs on Laurasia (the northern continents) during the Cretaceous Period. 

Only the largest North American azhdarchids (such as the Quetzalcoatlus) exceeded the Tropeognathus in size.

This pterosaur had an elongated skull, a relatively long neck, and an impressive wingspan that was up to eight meters (27 feet) or more. 

Gage Beasley Prehistoric's Tropeognathus Size Comparison
Gage Beasley Prehistoric’s Tropeognathus Size Comparison

It was about eight feet long from tail to beak and weighed up to 100 pounds.

Tropeognathus had a streamlined and elongated body typical of many pterosaurs. 

One of the most distinctive features of this flying reptile was its large skull. 

The skull was 0.6 to 1 meter (25 to 39 inches) long and had a long beak-like projection. 

At the tip of this elongated jaw was a large semi-circular crest with a length of about 23 centimeters (9 inches) and up to 10.5 centimeters (4 inches) tall.

Restored fossil skull of Tropeognathus, notice its prominent keel-like crest on its snout
Restored fossil skull of Tropeognathus, notice its prominent keel-like crest on its snout | Ghedoghedo via Wikipedia (CC BY-SA 3.0)

The lower jaw of the Tropeognathus also had a similar crest, but this one was smaller than the upper jaw. 

The mandibular crest was about 13 centimeters (5 inches) long with a depth of five centimeters (2 inches).

This pterosaur’s name, “keel jaw,” refers to these prominent keel-shaped crests.

The crests on the upper and lower jaws of the Tropeognathus were larger and more prominent compared to those of its close relatives like the Ornithocheirus and Coloborhynchus.

This resulted in a much broader skull compared to that of its relatives. 

The wings of the Tropeognathus were large and well-developed as well. 

It was formed by a wing membrane that stretched between its elongated finger bones. 

This membrane allowed for powered flight, and Tropeognathus would have been an agile and skilled flier.

Habitat and Distribution

Tropeognathus lived during the Early Cretaceous Period about 110 million years ago.

This pterosaur inhabited what is now modern-day Brazil and other parts of South America. 

During this period, the landmass of South America was still a part of the larger landmass of Gondwana, which included other southern continents, including Africa, Antarctica, Australia, India, and Madagascar. 

This pterosaur’s habitat was in a rift valley environment formed as the landmass of South America began to separate from Africa. 

This valley was filled with several lakes, and parts of it were periodically covered by the Atlantic Ocean. 

As an aerial hunter that targeted prey in the water, Tropeognathus lived near the lakes and marine waters found in this region.

Tropeognathus | Racksuz via Getty Images

These coastal areas provided abundant food sources for this pterosaur, and the proximity to water would have allowed it to take advantage of thermals and updrafts to aid its flight. 

During the Early Cretaceous Period, the Southern Hemisphere, where this pterosaur lived, was warmer than its current condition, and there were no polar ice caps. 

The climate of this region was tropical to subtropical in many regions and would have supported diverse ecosystems.

Sea levels were relatively high as well. 

This led to the formation of inland lakes, shallow seas, and other marine habitats that were crucial for the survival of flying reptiles like the Tropeognathus.

Behavior and Diet

Tropeognathus | Joshua Tedder via Pteros

Tropeognathus was a pterosaur, which means it was capable of flight. 

The large wingspan and developed wing membranes of this pterosaur suggest that it was an agile flier. 

It likely spent a significant portion of its life in the air, soaring above the waters of the coastal regions where it lived. 

Pterosaurs like Tropeognathus are believed to have been able to take off from both land and water.

While the wings of the Tropeognathus were long, they were also very thin. 

To support its heavy weight in the air, this pterosaur would have had to rely on a flight principle known as dynamic soaring

This involves using air currents generated by ocean waves to generate lift and pick up speed instead of flapping its wings continuously. 

Tropeognathus was a piscivore, which means it lived primarily on fish. 

To obtain food, this pterosaur would glide low over the water’s surface, using its keen eyesight to spot fish near the water’s surface. 

What the Tropeognathus looks for when hunting | danilovi via Getty Images

It was capable of swooping down and snatching fish from the water using its long, toothed jaws.

The upper jaw of the Tropeognathus had 13 pairs of teeth, while the lower jaws had 11 pairs. 

All of these teeth were concentrated near the front end of the jaws. 

The teeth are stout and slightly recurved—an adaptation for holding on to slippery prey. 

The unusual “keel jaw” of this flying reptile was also well-suited to the task of diving into the water to capture fish. 

Like other pterosaurs with toothed jaws, the Tropeognathus’ teeth were adapted for holding on to prey but not for chewing. 

This means it would have had to swallow prey whole.

The social behavior of Tropeognathus is not well-known. 

Pterosaurs, in general, are known to exhibit a wide range of social behaviors, from being solitary to gregarious. 

It isn’t clear if Tropeognathus individuals lived and hunted alone or formed social groups. 

Life Cycle

Holotype specimen of Tropeognathus
Holotype specimen of Tropeognathus mesembrinus (BSP 1987 I 46) in lateral (A1), palatal (A2), and anterior (A3) views | Borja Holgado and Rodrigo V. Pêgas via Acta Palaeontologica Polonica (CC BY-SA 4.0)

Like other flying reptiles, Tropeognathus most likely reproduced by laying eggs. 

The large keel on this pterosaur’s skull was larger in males than in females, suggesting some sort of mating display. 

After mating, the pterosaurs laid eggs in nests they made on the ground or rocky outcrops. 

The precise details of the Tropeognathus’ nesting behavior are not well-known, but evidence from related pterosaurs suggests that they may have nested in colonies. 

Scientists once found a fossilized pterosaur nest with up to 215 eggs, which suggests that these flying reptiles laid their eggs in communal nesting sites. 

The incubation period of Tropeognathus eggs likely varied depending on environmental conditions, but it could have taken several weeks.

Tropeognathus | Racksuz via GettyImages

The hatchlings of the Tropeognathus were small but generally similar to adult forms. 

Scientists have argued for years about how long it took pterosaur hatchlings to fly after birth. 

If they were incapable of flight, the parents would have had to provide some level of parental care, including feeding and protecting them from predators.

Tropeognathus hatchlings grew rapidly and would not have had to depend on their parents for long. 

As they grew, they developed the ability to fly and forage on their own, becoming fully independent after a few weeks.

Evolution and History

Reconstructed skeleton, National Museum of Brazil
Reconstructed skeleton, National Museum of Brazil | Dornicke via Wikipedia (CC BY-SA 4.0)

Tropeognathus was a pterodactyloid pterosaur. 

This means it belongs to a suborder of pterosaurs that contains the more derived flying reptiles. 

Pterodactyloid pterosaurs evolved during the Middle Jurassic and were around until the end of the Cretaceous Period. 

Unlike the primitive rhamphorhynchoid pterosaurs, pterodactyloid pterosaurs had short tails and long hand bones to which their wings were connected. 

The most advanced members of this group of pterosaurs lacked teeth in their jaws. 

Tropeognathus in Jurassic World Evolution
Tropeognathus in Jurassic World Evolution | Photo via Jurassic World Evolution Wiki

Tropeognathus had toothed jaws, which means it was not as advanced as the toothless pterodactyloids that evolved later in the Cretaceous. 

The toothed jaws of this pterosaur made it an efficient aerial hunter, capable of snatching fish and other prey from the water while in flight. 

Another unique adaptation of this pterosaur was its prominent head crest. 

Experts think the semi-circular crest of this pterosaur would have helped to stabilize its snouts when it is dipped into the water to catch prey, similar to the keel of a boat. 

Some of the closest relatives of the Tropeognathus within the Ornithocheirae clade have crests like this as well, but the Tropeognathus’ crest is larger compared to that of its relatives.

Interactions with Other Species

Tropeognathus | Racksuz via GettyImages

Tropeognathus was a top predator in the marine ecosystem of Cretaceous South America where it lived. 

It preyed mainly on fish and other marine prey, plucked right out of the water with its enormous beak-like jaws.

Although fish was the main food source for this pterosaur, Tropeognathus may have also preyed on other small marine creatures, such as crustaceans and cephalopods, opportunistically or as a secondary food source. 

While Tropeognathus was a top predator in its own right, it likely faced competition and predation risks from other creatures in its ecosystem.

In the coastal regions of the Late Cretaceous, large marine reptiles like the spinosaurids prowled the edge of the waters and could have posed a threat to flying reptiles like the Tropeognathus

Similarly, some large predatory fish or sharks may have occasionally preyed on Tropeognathus individuals, especially juveniles, whenever they landed on the water surface.

Different species of pterosaurs had similar or overlapping diets and habitats with the Tropeognathus and would have competed for the same food sources and other resources.

Cultural Significance

Hand puppet from Walking With Dinosaurs, Oxford Museum
Hand puppet from Walking With Dinosaurs, Oxford Museum | Simon via Flickr (CC BY 2.0)

Flying reptiles like the Tropeognathus are considered very important to paleontologists and evolutionary biologists. 

They’re valuable specimens for scientists trying to understand the evolution of flight and how this unique group of ancient reptiles became adapted to their ancient environment. 

The massive size of the Tropeognathus makes them an even more fascinating subject for scientific research. 

Tropeognathus was once featured on the BBC television program “Walking with Dinosaurs,” and its size was one of the major talking points of the documentary. 

Tropeognathus in Jurassic World: The Game
Tropeognathus in Jurassic World: The Game | Photo via Jurassic World: The Game Wiki

In the documentary, this pterosaur was erroneously referred to as Ornithocheirus mesembrinus

The genus Ornithocheirus refers to a close relative of this pterosaur, but both are completely unrelated. 

The wingspan estimate stated for the Tropeognathus in this documentary was 12 meters (39 feet). 

The size estimate was based on a specimen that was still being studied at the time the documentary was produced. 

The final description of this fossil found the wingspan to be about 8.70 meters (28.5 feet), meaning the size stated in the documentary was an exaggeration.  

Despite this, the Tropeognathus remains one of the largest pterosaurs ever discovered.


Tropeognathus was a large pterosaur that lived during the Early Cretaceous Period. 

This flying reptile was native to South America and is currently considered the largest flying reptile on the continent. 

It is most notable for its large cranial and mandibular crest or keel. 

Tropeognathus lived on the edge of lakes and coastal regions of South America at a time when the continent was still a part of the landmass of Gondwana. 

It was an efficient flier, capable of snatching fish and other aquatic prey out of the water with its massive toothed jaws.

As one of the largest flying reptiles ever discovered, Tropeognathus has been a fascinating pterosaur for scientists since its discovery in the 1980s. 

Large pterosaurs like this provide valuable insight into the life of the biggest flying vertebrates that have ever graced the planet and their impressive adaptations.


Why are pterosaurs not considered dinosaurs?

Flight characteristics, skeletal structure, and ecological niches distinguish pterosaurs from dinosaurs in the reptile evolutionary tree.

Pterosaurs had skin wings spread between long finger bones. They lived in the air and possessed hollow skeletons.

Dinosaurs were land-dwelling reptiles that could walk and run.

They possessed modified forelimbs that developed into wings in certain lineages but lacked pterosaur wing membranes.

Flight characteristics, skeletal structure, and ecological niches distinguish pterosaurs from dinosaurs in the reptile evolutionary tree.

What killed off the Tropeognathus?

Several reasons caused the extinction of pterosaurs like Tropeognathus.

Pterosaurs’ habitats and resources were likely altered by late Cretaceous temperature, sea level, and vegetation changes.

Pterosaurs may have been affected by birds vying for ecological niches.

Ecological imbalances and food shortages may have pressured their individuals.

Their extinction, along with dinosaurs’, may also have been caused by the end-Cretaceous mass extinction event.

Pterosaur extinction requires further investigation.

Who discovered the Tropegnathus?

In 1874, British paleontologist Harry Govier Seeley first described and named Tropeognathus.

Seeley categorized fossils found in England’s Cambridge Greensand Formation as belonging to a new pterosaur genus he named “Tropeognathus.”

More recent study and specimens have expanded our knowledge of this remarkable flying reptile.


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