November 18, 2010
Why a Pterosaur is Not a Dinosaur
A restoration of Pteranodon taking off by Mark Witton, lead author of the new PLoS One paper. Image from Mark Witton's Flickr page.
Earlier this week paleontologists Mark Witton and Michael Habib published a new study in PLoS One on how pterosaurs—particularly large forms such as Quetzalcoatlus—took to the air. Rather than pushing off the ground with their legs, pterosaurs used their arms in a pole-vault type of motion to launch themselves skyward. Interesting stuff, but I quickly became irritated by some of the popular coverage of the new research.
Whenever a story about pterosaurs makes it into mainstream news outlets, it is almost inevitable the flying archosaurs are going to be mistakenly called “dinosaurs” by at least one source. In this case the British newspaper the Telegraph and the venerable BBC were two of the main offenders, each declaring that pterosaurs were dinosaurs in their headlines.
It might be easy to brush off my complaint as a case of paleo-pedantry, but word choice matters. “Dinosaur” is a word for a specific group of creatures united by shared characteristics and which had their own evolutionary history—it is not a catch-all term for anything reptilian and prehistoric. Calling a pterosaur a dinosaur is an error of the same order of magnitude as saying that our species is a marsupial, but to understand why we need to flesh out the evolutionary relationships of these animals.
A close up of the relationship between dinosaurs and pterosaurs. Pterosaurs are underlined in red, and dinosaurs are underlined in green. Image modified from Wikipedia.
Let’s start from the bottom and work our way up. The Archosauria is a diverse group of reptiles which contains two major subsections: crocodiles and their close relatives (collectively called crurotarsans or pseudosuchians) are on one side of the split, and dinosaurs, pterosaurs, and their closest relatives (called avemetatarsalians) on the other. For our purposes here, we’re concerned with the second group.
Looking at the Avemetatarsalia (see the diagram above), a major split is apparent at the base of this group. On the one side are the dinosaurs and their closest relatives, and on the other are pterosaurs and animals more closely related to them than dinosaurs. Both pterosaurs and dinosaurs are distinct groups that shared a common ancestor, and so to call a pterosaur a dinosaur is to ignore this major divergence in the evolution of both groups. A pterosaur is no more a dinosaur than a goldfish is a shark.
There is no reason for news sources to keep applying the word “dinosaur” to pterosaurs. We have known about this distinction for a long time, and I bet that your average 10-year old paleo fan would know not confuse the groups. With even just a tiny bit of an evolutionary perspective, the distinction becomes clear.
To learn more about pterosaurs, visit Pterosaur.net, which was recently created by a team of pterosaur experts including Witton and Habib.
Sign up for our free email newsletter and receive the best stories from Smithsonian.com each week.
15 Comments »
RSS feed for comments on this post. TrackBack URI
Very good! But while you’re at it, you ought to show that ichthyosaurs, mosasaurs, plesiosaurs, and pelycosaurs aren’t dinosaurs either.
What? Aren’t dinosaurs anything lived a long time ago? LOL
IDK, these stem and node names change in who (or what almagamation of characters) they encompass and we’re not going to get the BBC to call them all Avemetarsalians, jeez I have a headache just saying that.
So what does it take to move “Dinosauria” to include pterosaurs too? How many character shifts? Much of that -distance- in the tree is poorly represented right? The line “other organisms more closely related to Pterosaurs” is funny since there aren’t really any except dinosaurs and this Scleromochlus thing I wiped off the bottom of my shoe.
Maybe make Dinosauria = Ornithodira….just a thought. The general public will never really care about the difference (just scientists and their jargon), and this battle is obviously eternal.
obviously this plan wouldn’t work with other “dinosaurs” but hey, with this new definition Dinosaurs can claim the evolution of flight 2x…Ooooo or the 1st dinosaurs were volant and everything else is secondarily terrestrial. Thats! a great story.
Of course, you are right, Brian, but it is still pretty picky, or “paleo-pedantry”, and, though you might be right too in that a keen young kid interested in dinosaurs would know, these media are not for keen young “paleo fans”, but for ignorant adults for whom it is not worth adding a piece of explanation as long as this blog piece when you want to indicate what a pterosaur is. Say dinosaur and even ignorant people get the gist of what you are talking about. I suppose on a web page you could put “dinosaur” used in this inaccurate but handy way in quotation marks and hyperlink it to an explanatory page, but not in a newspaper. But, yes, you are right. Paleo-pedant!
Stem-dinosaurs. Also pan-dinosaurs.
This frustrates me epically too. And everyone always says I’m being pedantic.
While we are being pedantic, the alternative practice of pterosaurs “flying reptiles” as a distinction from “dinosaurs” seems to be only slightly less inaccurate, as “reptile” is not a monophyletic group, and based on the phylogeny there is no reason to say dinosaurs are not reptiles, if pterosaurs are.
Maybe we should just call them pterosaurs?
When I was a 10-year old paleo fan I learned to use the term Dinosaur as a collective term for all reptile-like critters before 65 myo, and there was no confusion. I see on the taxonomy that there are 3 branches with the first 8 letters being Dinosaur…, there needs to be a new collective term for “all reptile-like critters that lived before 65 myo” or nearly every non-paleo-pedantic will continue to just use ‘dinosaur’.
I cannot believe how difficult you made the search for this info and why you finally listed under Dinosaurs after claiming it was NOT a dinosaur. What an annoying waste of time–I finally located the data under Google.
Why not simply call them “ancient flying creatures?” That certainly sets them apart from the ground-based dinos.
Fascinating…but what I really want is a big illustration of the whole darn evolutionary tree here…(where do mammals fit into this?). The average mundane non-scientist might be boggled by Latin verbiage; but a picture (an illustration of how it all fits together) is worth a thousand avemariatarsiers…
You know, if you’re going to be pedantic about this maybe you should rename your blog Avemetatarsalia Tracking. Someone might read one of your other blog posts about pterosaurs and get the impression they are dinosaurs based on the name of your blog.
I’m sure many science-loving people who will be forever ignorant of the specifics of the evolutionary tree of ancient creatures do still understand that the technically correct use of the term “dinosaur” really does matter to the paleo-educated. But what can be done? It’s a toughie. Certainly the public needs a word to mean what it currently uses to describe those ancient and strange creatures that were discovered via fossils or impressions left in rock. Maybe paleontologists can find a replacement for the scientific “dinosaur” or could create a different but similar, reasonably pronounced and remembered word can that will work in place of the general public’s “dinosaur”. Avemetatarsal won’t work. The public will feel that it has some right to what it understands “dinosaur” to be. But like changing Coke’s recipe or kicking Pluto out of the planet club, perhaps such an effort, if launched correctly and in humility, could at least stir up a little public controversy and discussion about your craft and science. But if it becomes obvious that usage will not change or the whole effort simply polarizes the public and the paleontology community, keep the big picture in mind, admit defeat gracefully, and be happy that a few more of the general public know that “dinosaur” has a related but separate, scientific meaning.
I agree with those calling this paleo-pedantry. Seems to be a language use argument, between a narrow definition of “Dinosaur” as used by some scientists and the somewhat wider, inclusive use of “Dinosaur” by everyone else.
Language is alive and can’t successfully be imposed on by anyone, though it can be influenced.
For me to be convinced to call a Pterosaur an Archosaur or something else other than a type of dinosaur or dino-bird, by the wider definition, I and most people would want not arcane latin name diagrams but concrete reasons. What about a Pterosaur makes it not a dinosaur?
And BTW, on Brian Switek’s own diagram, “Dinosauromorphs” leads to “Pterosaurs” which would seem to counteract his argument, since the Latin-Greek term itself (“Dinosaurmorphs”) shows its Dinosaur relatedness; as does the “Saur” part of “Pterosaur.”
I think this a great article but I still don’t completely understand why pterosaurs aren’t dinosaurs