This is Pterodactylus. Well, it was. It’s now called Scaphognathus and for those who know, it’s really not even very close to Pterodactylus as pterosaurs go (for a start, it’s a non-pterodactyloid) with a positive hatful of characters that clearly separate the two.

Of course taxonomic revisions are a constant theme of palaeontology, but this would seem to be a rather extreme case. Part of this of course is down to the age of the original specimen (the photo above is of a cast), consistent taxonomy is hardly at a peak now, so back in the early 1830s, dramatic lumping of this kind can hardly be considered a huge sin in hindsight. However, this is also a good demonstration of a far more common issue in biology as a whole: the more data you have, the harder it can be to sort out your taxonomy as previously distinctive characters can turn out to be less useful that originally thought.

Consider the pterosaurs. When the original Pterodactylus specimen turned up, it was obviously completely different to anything else then known. You could instantly distinguish it from any other vertebrate by the wing finger alone, let alone anything else in the skeleton. It was then perhaps not a surprise that the next few pterosaurs to appear, like Scaphognathus, despite some obvious differences, were put into Pterodactylus based on their even more obvious similarities  – these were, after all, obviously pterosaurs. However, once it became clear that there were some important differences, as well and the similarities, then thinks like Dimorphodon and Scaphognathus were separated out into their own genera. This is an extreme example, but the principle is the same and constantly resurfaces.

Even the best taxonomic work and definitions can eventually crumble under the weight of new data, and if the original was also based on rather poor material or what turned out to have little going for it apart from characters that are no longer unique, then still more problems will inevitably arise. Thus what this ultimately boils down to is the fact that taxonomy is always going to be an ongoing process. Not only does every new taxon need to be described and diagnosed, but a large part of the time, this has a knock-on effect meaning that other things now also need to be revised or redefined as a result of the new information. As I have lamented before, taxonomy as a field, both in biology and palaeontology seems to be every dwindling as money is funnelled into for ‘sexy’ subjects, despite basic taxonomy being the absolute foundation of all biological research and this underappreciated field can only cause problems if this trend continues.

8 Responses to “‘Pterodactylus’”

  1. 1 Mark Robinson 02/01/2011 at 4:56 pm

    Dave, other morphological differences notwithstanding, isn’t the type specimen missing its tail, which would therefore make its initial classification as a pterodactyloid perhaps not so egregious?

    • 2 David Hone 02/01/2011 at 5:22 pm

      Well it’s not there in that one (which is the Scaphognathus holotype) no. But still, it is incredibly different, almost all the other pterodactyloid characters are obviously not there (no NAOF, no big skull, no long neck, no big metacarpal, no big pteroid, the cervical ribs are still there etc.) and the head and tooth shape alone should do it.

      I still understand how it happened, but come on Dimoprhodon and Rhamphorhynhcus used to be in Pterodactylus. Even by the standards of early 1800s taxonomy, that seems rather excessively lump-y.

  2. 3 Matt Martyniuk 02/01/2011 at 8:05 pm

    Good post, but I wonder if in this case it’s more an issue of different taxonomic philosophies than new data. After all this as never referred to as the species Pterodactylus antiquus, just the genus Pterodactylus. Genera are totally arbitrary, so it wasn’t “incorrect” to place it there. As more an more morphological diversity was found in Pterosauria, people started to break up the increasingly large genus Pterodactylus, but really, it wouldn’t necessarily be incorrect to place ALL pterosaurs in Pterodactylus either.

    In fact, I wonder if something like PhyloCode had been around back then, and Pterodactylus was formally defined by its unique (at the time) characters, whether we would now be REQUIRED to refer to all pterosaurs as Pterodactylus.

    • 4 David Hone 02/01/2011 at 9:11 pm

      Well yeah, all low level taxonomy is arbitrary. But I don’t think *anyone* would put all pterosaurs into a single genus. Of course you can have low level lumping and splitting (is Tarbosaurus separate from Tyrannosaurus) but that’s pretty minor. I think actually many of them were in P. antiquus originally. But this is merely an extreme example, the general issue of changing definitions is a real one. Imagine we find something effectively identical to say Archaeopteryx except with twice as many teeth. You really do need to then modify the definition to include this (“different to all other theropods based on X, Y and Z *except* Newtaxon wich is identical except in tooth count”). The validity of the taxa don’t change but quite how you define them does.

  3. 5 Thomas R. Holtz, Jr. 03/01/2011 at 3:11 am

    Another specimen of “Pterodactylus” that turned out to be even further removed phylogenetically is P. crassipes (aka Archaeopteryx lithographica).

    • 6 David Hone 03/01/2011 at 9:11 am

      I’ve never found out exactly how that happened. While I’ve only seen low fidelity casts of the Haarlem specimen, it does seem to have feather impressions.Even by the standards of taxonomy then, it seems odd that it was considered a pterosaur.

      • 7 vasha7 08/01/2011 at 9:20 pm

        I was just reading Switek’s Written in Stone and he talks about how Basilosaurus got its name. Richard Harlan of the American Philosophical Society examined its bones in 1834 and thought it was a giant reptile, even though he was surprised by its mammalian teeth: Switek suggests that he was influenced by the fact that at that time, “many geologists thought that there was a temporal dividing line between the ‘Age of Reptiles’… and the subsequent ‘Age of Mammals.’ Mammals could not have survived among the marauding reptiles, it was thought, and instead represented the next progressive step in the succeeding era.” (And Harlan didn’t know the exact age of Basilosaurus, just that it was old.) Perhaps the mind of the person who named Pterodactylus crassipes was running in a similar way: ancient = primitive = reptile ergo like previously-named flying reptile?

      • 8 David Hone 09/01/2011 at 7:01 pm

        Well I’m not commenting on the name, but the taxonomy. Nothing wrong with the name Pterodactylus, quite a bit wrong, (despite, i think, the hindsight) with assuming every pterosaur, no matter how different from the first, went into just one genus.

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