The image of prehistoric skies filled with giant flying reptiles often leads to confusion about their proper names. Many people use the term “pterodactyl” as a general label for any extinct winged reptile. However, this common name refers to a specific, relatively small animal and is frequently misapplied to the much larger creature that matches the popular image. Understanding the relationship between these two requires examining their place in the broader family of flying reptiles.
The Pterosaur Family Tree
The correct overarching group for all these ancient flyers is the order Pterosauria, meaning “winged lizards.” Pterosaurs were a separate lineage of reptiles that coexisted with dinosaurs during the Mesozoic Era. They were the first vertebrates to develop powered flight, achieved by a wing membrane stretching from an elongated fourth finger to the ankle. Within this order, scientists recognize two main sub-groups based on physical features.
The earliest flyers, such as the Rhamphorhynchoids, had long tails and relatively short necks. The later, more advanced group, the Pterodactyloids, evolved shorter tails and longer necks, allowing for greater agility in the air. Both the genus Pterodactylus and the genus Pteranodon are members of the Pterodactyloid sub-group, confirming they are related but distinct branches on the same family tree.
Pterodactylus Characteristics of the Early Flyer
The genus Pterodactylus represents one of the earliest and smallest known members of the Pterodactyloid lineage. It lived during the Late Jurassic period, approximately 150 million years ago, with most fossils found in the famous Solnhofen limestone of Bavaria, Germany. This creature was relatively modest in size, with wingspans ranging from about 0.5 to 1.5 meters, comparable to a modern eagle or vulture.
A defining characteristic of Pterodactylus was its long, narrow skull containing numerous needle-like teeth. Specimens have shown that it could possess up to 90 teeth, which were likely used to catch small fish and invertebrates in coastal environments. Although it possessed a small, soft-tissue crest on its head, this feature was not nearly as prominent as those seen in its later relatives.
Pteranodon Defining Features of the Late Cretaceous Giant
The genus Pteranodon appeared millions of years later in the fossil record, soaring over the seas of the Late Cretaceous period, around 85 to 75 million years ago. Its remains are found primarily in North America, particularly in the midwestern United States, which was once covered by the vast Western Interior Seaway. Pteranodon was a true giant of the skies, with males reaching impressive wingspans of up to 7 meters (over 23 feet), though females were noticeably smaller.
The most recognizable feature of Pteranodon is its prominent, backward-sweeping cranial crest, which was significantly larger and more varied in males than in females. This bony projection may have served as a rudder for stability during flight, a counterweight for its long beak, or, most likely, as a visual display for mating and species recognition. Unlike its earlier relatives, Pteranodon possessed long, slender jaws that tapered into a toothless, pelican-like beak. This adaptation suggests a diet focused on skimming fish from the ocean surface.
Teeth, Size, and Time Distinguishing the Two
The fundamental difference between these two genera comes down to three factors: teeth, size, and time. Pterodactylus was a toothed flyer from the Jurassic period, whereas Pteranodon was a toothless giant from the Cretaceous. Pterodactylus was a comparatively small animal, with a wingspan rarely exceeding 1.5 meters. In sharp contrast, Pteranodon was one of the largest flying reptiles, with a wingspan that could be four to five times greater. The anatomical distinction regarding their jaws is the clearest trait: Pterodactylus had a skull filled with sharp teeth, while Pteranodon had a completely smooth, bony beak. The final difference is the immense span of time separating their existence, as Pteranodon appeared millions of years after Pterodactylus had become extinct. The use of the informal term “pterodactyl” persists because Pterodactylus was one of the first pterosaurs discovered, leading to its name being incorrectly applied to the entire group.