What Is a Pterodactyl? A Word That Means Less Than People Think

Pterodactylus is a genus named in 1809 from specimens in the Solnhofen limestone of Germany, and its members were small, with wingspans generally under a metre and a half, with long jaws bearing small teeth and a modest head crest in some specimens. It is one genus within the pterodactyloid group, which is itself one of the two main branches of pterosaurs. The creature most people picture when using the word, with a long backward-pointing head crest and a toothless beak, is Pteranodon, named in 1876 from North American chalk, which is a different genus, considerably larger, from a different continent and around eighty million years later. The word pterodactyl entered English as an anglicisation and spread as a general term for any flying prehistoric reptile, which is not how the naming works, since pterosaurs include well over a hundred named genera spanning more than one hundred and fifty million years and differing enormously in size, diet and appearance.

Several reinforcing factors keep an obsolete usage alive:

• •The name was among the first applied to the group and predates most of the others, so it entered general vocabulary before the diversity was known
• •It is easier to say and to remember than the technically correct alternatives
• •Popular culture fixed the image, with illustrations, films and cartoons showing a crested toothless form under the familiar name
• •The animals are frequently grouped with dinosaurs in the same books and exhibits despite not being dinosaurs, which compounds the error
• •No convenient general term exists in common speech, since pterosaur is accurate and unfamiliar
• •Correction is socially awkward, since the word communicates successfully to most listeners even while being wrong

The group is worth knowing accurately because the range is more interesting than the single image:

• •Rhamphorhynchus and other early long-tailed forms, small with a diamond-shaped vane at the tail tip
• •Pterodactylus and its relatives, the short-tailed group that includes most later genera
• •Pteranodon, toothless with a long backward crest, from North American seaways, which is the animal most pictures actually depict
• •Quetzalcoatlus and other azhdarchids, with wingspans around ten metres and a standing height comparable to a giraffe, generally reconstructed as stalking prey on the ground
• •Filter feeders with hundreds of fine bristle-like teeth, which strained small organisms from water
• •Forms with head crests larger than the rest of the skull, whose function is display rather than anything aerodynamic

Several related misconceptions travel with the name. Pterosaurs are not dinosaurs and are not ancestral to birds, being a separate group of archosaurs that evolved flight independently and left no descendants. They did not have feathers in the avian sense, though many carried a fur-like covering whose relationship to feathers is under debate. They did not flap like bats, since the wing is supported by a single elongated finger rather than by four. They were not all large, with several species smaller than a blackbird. They did not hang upside down as a rule, and trackways show them walking competently on all fours with the wings folded. And they did not glide exclusively, since the anatomy supports powered flapping flight, though the largest species raise genuine questions about how much flapping they could sustain. Each of those errors is durable because the correct version is less striking than the picture already in circulation.

The general lesson concerns the relationship between scientific and popular naming. Scientific names are precise, unstable in usage as classifications are revised, and unfamiliar. Popular names are memorable, stable and imprecise, and they attach to whichever example was encountered first rather than to a defined group. That mismatch produces recurring problems, including velociraptor for a group of much larger animals, brontosaurus for a name that was sunk as a synonym and then partially revived, and the general use of dinosaur for anything extinct and large. Insisting on precision in casual speech is unproductive, since the purpose of the word is to communicate and it does. The useful position is to know what the word properly refers to, to recognise that the picture in most people's heads corresponds to a different animal, and to introduce the accurate terms where the distinction matters, which is generally when the diversity of the group is the interesting part.

The name belongs to one small German genus from 1809, while the crested toothless creature people picture is a different genus from a different continent eighty million years later. Pterosaurs include over a hundred genera, are not dinosaurs, are not ancestral to birds and walked competently on all fours. The word survives because it arrived first, is easy to say and communicates successfully despite being wrong.