Come Fly with Me

I know pterosaurs aren’t dinosaurs, but it feels like they should be, right? I mean I get it, dinosaurs are defined by their skeleton and evolutionary history, all sharing an upright posture^{1: Go to reference 1 at the end of the page} yadda yadda yadda. But I didn’t grow up playing “dinosaurs and their somewhat-related reptile cousins who happen to fly and / or swim”. I just played dinosaurs.^{2: Go to reference 2 at the end of the page} Pterosaurs were flying-dinosaurs and marine reptiles, like the ichthyosaurs and plesiosaurs, were water-dinosaurs.

When I say I love dinosaurs, I assume you know what I mean. I love all the old reptiles that stomped, soared, and swam throughout the Mesazoic and beyond. Sure, a rauisuchian^{3: Go to reference 3 at the end of the page} is not a dinosaur, but if you found yourself transported back to the mid-Triassic and being chased by one, you probably wouldn’t be able to tell the difference (or care to try).

Around 80 million years after dinosaurs first appeared, one lineage would eventually evolve the ability to fly and give rise to the first birds,^{4: Go to reference 4 at the end of the page} but long before that, pterosaurs ruled the skies. They aren’t dinosaurs, but both groups are archosaurs and are still closely related.

We believe their most recent common ancestor was ~250 – 245 mya (million years ago), in the early Triassic.^{5: Go to reference 5 at the end of the page} The oldest dinosaur fossils we’ve found date back to ~243 mya^{6: Go to reference 6 at the end of the page} and the oldest pterosaur fossils date back ~228 mya.^{7: Go to reference 7 at the end of the page} So in geological time, they’re basically first-cousins.

Thanks to the fossil record, and the incredible paleontologists who continue to expand it, we’ve discovered many transitional species that shed light on the evolution of extinct animals. But when it comes to pterosaurs, the picture is still a bit hazy.

Rhamphorhynchoidea^{16: Go to reference 16 at the end of the page} is not a real genus, more like an informal grouping of the earliest, most basal pterosaurs. The term is considered outdated, and the name “non-pterodactyloid pterosaurs” is usually seen as more accurate, but who wants to be named after what you aren’t? It’s like Care Bears and Care Bear Cousins all over again. Brave Heart Lion deserved better than to be just another “Care Bear Cousin”, he was his own plushy man-lion.^{17: Go to reference 17 at the end of the page}

These early pterosaurs often shared features that would be less common in their later relatives, like a long tail, rows of sharp teeth, and relatively small bodies compared to the gargantuan flyers they would one day evolve into. (ouuuuu…. foreshadowing)

The name rhamphorhynchoids was derived from a real species of early pterosaurs known as rhamphorhynchus (beak snout), that existed ~160 – 145 mya. They had curved,  needle-like teeth, which were angled forward, suggesting a diet consisting mostly of fish, and their stomachs were often found with fish and cephalopod remains inside.

The largest and best-known species was rhamphorhynchus muensteri. We’ve estimated their maximum wingspan to be about 1.8 meters, but they likely weighed no more than 1 – 2 kg due to their small bodies and hollow bones.

Although these flying baddies were mostly piscivores, we believe the earliest pterosaurs were actually insectivores. Species like Eudimorphodon^{18: Go to reference 18 at the end of the page} (true two-form tooth) and Carniadactylus^{19: Go to reference 19 at the end of the page} (Carniola finger) had multicusped teeth that were adapted to crush and pierce exoskeletons. The earliest species of pterosaurs known, preondactylus^{20: Go to reference 20 at the end of the page} (Preone finger) from ~228 mya, had small, sharp, conical teeth that were ideal for small prey. We believe they were mostly insectivorous, possibly supplementing it with small aquatic animals.

One of the better known rhamphorhynchoids was Dimorphodon^{24: Go to reference 24 at the end of the page} (two-form tooth). They were fairly robust for the flyers of their time. They could reach 3 – 4.5 meters, depending on the species, and unlike the typical sleek, lightweight pterosaur, they were stockier, hinting they may have spent more time walking or climbing than flying.

They had two types of teeth, hence where they got their name. Most early pterosaurs had uniform teeth but Dimorphodon had large fang-like teeth at the front and smaller, shearing teeth at the back. Their long stiffened tail balanced their large, boxy head and although they did eat insects, we believe they may also have hunted small vertebrates.

They are often depicted hunting in water but analyses suggest their jaw structure was not actually well-suited for catching fish.

160 mya, in the late Jurassic, a new clade of pterosaurs emerged from within one of the early lines of rhamphorhynchoids. Unlike the earlier pterosaurs we’ve discussed, the pterodactyloids^{25: Go to reference 25 at the end of the page} were all part of one true clade, a single, monophyletic group descended from a common ancestor.

Unlike their predecessors, these pterosaurs had:

• longer metacarpals (hand bones).
• shortened tails.
• larger skulls with longer jaws.
• bigger, more elaborate head crests (in some species).
• toothless beaks (in later forms).

The earliest known pterodactyloid is kryptodrakon.^{26: Go to reference 26 at the end of the page} It had an estimated wingspan of 1.5 meters and its fourth finger was narrow and prolonged, a strong sign it was a pterodactyloid. The relative proportions of the bones in their fourth metacarpal are within the range of pterodactyloids, but a study defined them as a sister species to all others in the clade.

Kryptodrakon fossils are usually found in in-land habitats, leading a study’s authors to theorize that pterodactyloidea had a terrestrial origin.^{27: Go to reference 27 at the end of the page} Their relatively short wings also support this idea, since modern birds with long wings are typically coastal, while those with shorter wings are more often found in forests.

The pteranodon^{29: Go to reference 29 at the end of the page} is another well-known pterosaur, instantly recognizable by its fantastic backward-sweeping head crest. It’s a staple in dinosaur media, appearing everywhere from Jurassic Park to toys, documentaries, and online paleoart. Its popularity also stems from its remarkable size. Adult males are estimated to have had wingspans approaching 6 meters, nearly double that of the Wandering Albatross, the living bird with the broadest wingspan. Unlike earlier, more modestly sized pterosaurs, pteranodon marks a clear turning point in their evolutionary trend toward gigantism. It was not yet at the scale of the true giants like quetzalcoatlus, but it foreshadowed their arrival.

The discovery of hundreds of well-preserved Pteranodon fossils has provided evidence for sexual dimorphism^{30: Go to reference 30 at the end of the page} within this species. Detailed analyses, notably by paleontologist S. Christopher Bennett, revealed two distinct morphs: larger individuals with expansive wingspans, robust limb bones, and prominent cranial crests, and smaller individuals with more delicate builds and modest crests.^{31: Go to reference 31 at the end of the page} Pelvic bone examinations indicated that the smaller morphs possessed wider pelvic canals, suggesting they were females, while the larger morphs with narrower hips were males. This sexual dimorphism implies that males may have used their pronounced crests for visual displays to attract mates or assert dominance.

Pterodactyloids weren’t all giants, early species displayed a wide range of sizes and forms. Notably, Pterodactylus^{32: Go to reference 32 at the end of the page} and Aerodactylus^{33: Go to reference 33 at the end of the page} (sound like brothers in a Greek tragedy) were relatively small compared to their later relatives. Despite their modest dimensions, these species played a crucial role in the evolutionary narrative of pterosaurs, showcasing the diversity and adaptability of early pterodactyloids.

Pterodactylus holds historical significance as the first pterosaur to be scientifically described, dating back to the late 18th century. Fossils of this genus, primarily found in the Solnhofen Limestone^{34: Go to reference 34 at the end of the page} of Bavaria, Germany, reveal a average wingspan in adults of about 1m, indicating a small yet agile flier. Its elongated jaws, filled with sharp teeth, suggest a diet consisting of fish and small marine organisms. The combination of a short tail and elongated metacarpals distinguishes it as a true pterodactyloid, marking a significant step in the evolution of more advanced flight adaptations.

Aerodactylus, another pterosaur from the Late Jurassic of Germany, was initially classified under Pterodactylus but later recognized as a distinct genus due to differences in skull and limb bone morphology.^{40: Go to reference 40 at the end of the page} Known from juvenile specimens with wingspans around 0.45 meters, it’s estimated that adults may have reached wingspans of approximately 0.9 meters. These fossils, though rarer, provide valuable insights into the diversity of early pterodactyloids and suggest a lifestyle similar to Pterodactylus, likely involving hunting small prey in coastal environments.

Collectively, Pterodactylus and Aerodactylus exemplify the early experimentation in body forms that characterized pterodactyloid evolution. Their fossils offer a window into the morphological diversity and ecological adaptability that would eventually give rise to the larger and more specialized pterosaurs of the Cretaceous period. These early species underscore the evolutionary flexibility that was a hallmark of pterodactyloid success from their inception.

After pterodactyloids emerged in the Late Jurassic, the more primitive rhamphorhynchoids gradually declined and had mostly disappeared by around 145 million years ago.^{49: Go to reference 49 at the end of the page} Over the Cretaceous, non-azhdarchid pterodactyloids such as ornithocheirids and tapejarids also dwindled, while azhdarchids rose to dominance.^{50: Go to reference 50 at the end of the page} By about 72 million years ago, azhdarchids were the most widespread pterosaurs, and in the final 6 million years before the K–Pg extinction, they were likely the only surviving group until the asteroid impact around 66 million years ago ended the reign of all remaining pterosaurs and non-avian dinosaurs alike.^{51: Go to reference 51 at the end of the page}

Azhdarchids are united by several features, including their extremely long, stiff necks made of elongated vertebrae and toothless, spear-like beaks. They had proportionally large heads and short, robust bodies, often with relatively narrow wings. Unlike many other pterosaurs, they likely spent much of their time walking on land, using long limbs and an efficient quadrupedal gait. Fossil evidence and limb proportions suggest they were well-adapted for stalking prey in open environments like floodplains.^{52: Go to reference 52 at the end of the page}

Albadraco tharmisensis^{53: Go to reference 53 at the end of the page} is currently the earliest known azhdarchid, dating to the early Late Cretaceous, around 86 – 84 million years ago. Discovered in Romania, it is known from fragmentary skull and jaw material, which still shows typical azhdarchid traits like a long, toothless beak. Its remains suggest it was a medium-sized member of the group, not quite as big Quetzalcoatlus but still with a wingspan of 5 – 6 meters. Albadraco helps fill the gap between earlier pterodactyloids and the later dominance of azhdarchids in the final stages of the Cretaceous.

Named after Quetzalcōātl, the Aztec feathered serpent god, Quetzalcoatlus^{54: Go to reference 54 at the end of the page} is one of, if not the, largest azhdarchid ever. As tall as a giraffe and weighing as much as a grizzly bear, these Cretaceous giants must have been a breathtaking sight… when admired from a safe distance. With massive wingspans and elongated necks, they cut a striking figure across the ancient landscape. Fossils found in what was once an inland coastal plain suggest they favoured open, flat environments where their height gave them a clear view over potential prey or rivals.^{55: Go to reference 55 at the end of the page}

For years, Quetzalcoatlus served as a kind of “wastebasket taxon” for large azhdarchid fossils in North America, especially fragmentary bones resembling the original Quetzalcoatlus northropi material discovered in the 1970s. This was largely due to the lack of detailed published descriptions, particularly of the holotype, which led researchers to lump similar remains under the same name.^{56: Go to reference 56 at the end of the page}

That changed in 2021, when a long-awaited monograph finally offered a detailed description of both Quetzalcoatlus northropi and a smaller species, Quetzalcoatlus lawsoni.^{57: Go to reference 57 at the end of the page} This landmark publication not only clarified their anatomy and differences, but also helped paleontologists sort out which fossils truly belonged to the genus. As a result, several specimens once assumed to be Quetzalcoatlus were reassigned or reexamined, and researchers now have a clearer picture of its biology and biomechanics, including how it may have taken off using a powerful quadrupedal launch.^{58: Go to reference 58 at the end of the page}

Despite their enormous size, these creatures could fly, and recent studies suggest they were strong, efficient gliders capable of traveling long distances.^{59: Go to reference 59 at the end of the page} However, the image of Quetzalcoatlus soaring high above ancient coastal plains is only half the story. Their long limbs, stiff necks, and toothless beaks were just as suited for stalking prey on the ground, possibly ambushing small dinosaurs or scavenging carcasses. With their strange mix of aerial prowess and grounded hunting ability, Quetzalcoatlus may have been one of the most versatile, and intimidating, predators of the Late Cretaceous.

As a Canadian, I have a real love for Cryodrakon boreas^{60: Go to reference 60 at the end of the page} (frozen dragon of the north winds🤘), a medium-to-large azhdarchid found in Alberta, Canada’s Dinosaur Park Formation. This area is a prehistoric treasure trove of ancient life, where layered badlands and sediment-rich formations have preserved one of the most diverse and abundant fossil records on Earth.

Moth Light Media, the maker of the Cryodrakon video, is an outstanding YouTube channel. They don’t know me, I’m just a fan. They cover all types of prehistoric animals, and they select great music and visuals.

In general, the azhdarchids were much bigger than earlier pterosaurs, but there was still a lot of diversity in their sizes. Montanazhdarcho minor^{61: Go to reference 61 at the end of the page} was a smaller species found in Montana, U.S. They were still 1.5 m tall and had a wingspan between 2.5 – 3 m, but weighted only about 7 kg due to their smaller frames.

Phosphatodraco mauritanicus^{62: Go to reference 62 at the end of the page} was a small-to-medium sized azhdarchid found in Morocco, a country with a rich fossil history of pterosaurs. Standing 2.2 m tall, with a wingspan exceeding 5 m, these bulky boys had a estimated weight of 80 kg, which outweighs the average adult human. Zhejiangopterus linhaiensis,^{63: Go to reference 63 at the end of the page} which lived in late Cretaceous China, had a similar height and wingspan to Phosphatodraco, but was bulkier still, with an estimated weight of 120kg.

When discussing Quetzalcoatlus earlier, I said it may be the biggest pterosaur ever, and that’s because we aren’t 100 percent sure. Paleontology is a puzzle game, and we rarely get all the pieces. Even when we do, it’s usually just the bones. From those, scientists estimate size and weight using solid methods, but all numbers come with a margin of error.

Three species currently contend for the title of “biggest pterosaur ever.” Quetzalcoatlus is the most well-known, with two named species, the smaller Q. lawsoni and the larger Q. northropi, both found in the Javelina Formation in Texas.^{64: Go to reference 64 at the end of the page} While we have many fossil elements, including wings and limbs, no complete skeleton has been found.^{65: Go to reference 65 at the end of the page} The shape and size of the crest are still debated, and no soft tissues like the wing membranes were preserved, so some uncertainty remains in wingspan estimates.

Hatzegopteryx is less complete but very distinctive. A partial but thick skull and several short, dense neck vertebrae suggest a powerfully built animal.^{66: Go to reference 66 at the end of the page} These fossils come from the Hațeg Basin in Romania,^{67: Go to reference 67 at the end of the page} which during the Late Cretaceous was a subtropical island habitat. Its bones are unusually strong and dense compared to other azhdarchids, hinting at a different hunting strategy. It may have relied more on strength than reach, possibly ambushing prey on land. Its wingspan is estimated at around 10 to 11 meters, similar to Quetzalcoatlus, but it may have been heavier and more robust overall.

Arambourgiania is known from even fewer remains, most notably a single, extremely long neck vertebra found in Jordan, along with a few additional fragments.^{68: Go to reference 68 at the end of the page} No skull or full limbs have been recovered, which makes size estimates difficult. The original vertebra led to early wingspan estimates of 12 to 13 meters, but later studies revised that down to around 10.5 to 11 meters. It likely had a more slender frame than Quetzalcoatlus or Hatzegopteryx, which would have made it lighter. Without more fossils, though, its exact proportions and behavior remain uncertain.

* We have very limited fossil evidence for this species, so these numbers are uncertain and disputed.