Saturday, May 11, 2013

The Validity of Lambeosaurus - Anybody Know A Good Lawyer?

Reconstruction of Didanodon altidens specimen ROM 794 (aka Lambeosaurus lambei,
aka Procheneosaurus praeceps) by Matt Martyniuk, all rights reserved.
I've talked a lot on this blog about my personal justifications for using "old fashioned" names for many groups or species of stem-birds. In many cases, names which were in common use during the 19th and early 20th centuries were replaced later by one or two influential scientists for reasons which don't really hold up when you look at the codes that govern naming in biology. For example, Manospondylus gigas may currently be the correct name for the theropod we know and love as Tyrannosaurus rex, but this possibility has almost never been discussed because everybody assumes it's a nomen oblitum - a name out of use for so long that it becomes automatically invalid under the International Code of Zoological Nomenclature (ICZN). Note the word "assume"--as I've written before, most people, even working scientists, don't really know what criteria must be met to classify a name as obsolete.

The name of one very well-known dinosaur is in such a sorry state that it's like the Manosponylus / Tyrannosaurus debacle squared. The genus Lambeosaurus, a well-known hadrosaurid with a distinctive squared-off crest with a backward-pointed prong, was named twice prior getting its popular moniker, and neither of those names can be considered obsolete, since they were both coined during the 20th century.

The first name given to fossil material (in this case a jaw) now universally attributed to Lambeosaurus was Didanodon. In a 2006 review of hadrosaurs, Lund and Gates stated (without discussion) that the genus and its type species, Didanodon altidens, were nomina nuda, or "naked names" lacking the proper description necessary to establish them. But is this really the case?

The problem is that Didanodon was given its name in two parts, by different scientists in the same journal volume. Lawrence Lambe (the paleontologist who would later be honored in the name Lambeosaurus lambei) and Henry Fairfield Osborne co-edited a two-paper 1902 volume of the journal Contributions to Canadian Paleontology (part II), the entirety of which is public domain and can be downloaded as a pdf.

In his contribution, Lambe named and described a number of dinosaur species from what is now called the Dinosaur Park Formation of Alberta. One of these was a new species of hadrosaur which he classified in the genus Trachodon, as Trachodon altidens, based on a distinctive lower jaw. The description (on page 76 of the volume, see pdf) was fairly thorough, especially for the time, and nobody, not even nomenclatural sticklers, could possibly argue that T. altidens was not properly coined. In other words, there is no possible way to consider the name a nomen nudum as Lund and Gates did--it's too bad they did not provide any explanation for doing so.
Reconstructed Lambeosaurus
growth series by Nobu Tamuralicensed.

It's possible that Lund and Gates really intended to describe the genus Didanodon (not the species D. altidens) as a nomen nudum, but here's where things get sticky. Lambe, in his own paper, never considered T. altidens to be anything but a new species of Trachodon of the subgenus Pteropelyx. Osborne, on the other hand, suggested in his own section of the volume (page 19) that altidens could represent a new genus or subgenus, for which he proposed Didanodon. And that's the only mention I can find of the name Didanodon in the literature until 2006 (admittedly using a cursory Google Scholar search). It seems as though Osborne's name was either forgotten, completely overlooked, or dismissed as merely a non-binding suggestion.

Here's where the nomenclatural lawyering comes in. As typically interpreted, the ICZN mandates that a genus must be given a diagnosis and a type species to become "available" (official). However, for older papers, more leeway is given. Bear in mind that plenty of genus names that are accepted today went years without a clear type species (like Ornithocheirus, type species still a matter of dispute today!) or with no type species at all (like Pterodactylus). It is always possible to assign a type species to a genus at a later date without changing the status of the genus name as "available".

Furthermore, the ICZN provides that for any genus name coined before 1960, if only one species was included (i.e. the genus was monotypic when named), that species automatically becomes the type--a situation that would seem to apply to Didanodon altidens.

But can a genus named as basically an off-hand comment like that really be valid? This is controversial with other names, like Aviremigia, which was coined as a "suggestion" to be used if such a name is later deemed necessary. That name falls outside the purview of the ICZN, though, where anarchy will continue to rule until the establishment of the PhyloCode. Aviremigia is valid if you want it to be, and nobody can challenge you because there are no rules to do so by.

The ICZN, though, does have rules to govern the status of families, genera, or species named as "conditional proposals" (Article 15.1), and I think a statement which boils down to "this may be a new genus, in which case it is called Didanodon" is a clear case of a conditional proposal. It states that while any conditionally-proposed names coined after 1961 are invalid, those coined before 1960 may be valid if all the other conditions for naming a genus are met (i.e. it must be stated that the intent is to name a new genus, a type species is available, it's formed correctly when in Latin, etc.).

As far as I can tell, this is the case for Didanodon, which cannot, therefore, be considered a nomen nudum, contrary to Lund and Gates.

Ok, where does all this leave Lambeosaurus? There have generally been three widely-supported species assigned to Lambeosaurus: L. lambei, L. magnicristatus, and L. paucidens. L. paucidens is known from a paucity of material (see what I did there?), and is now generally considered either dubious or a synonym of L. lambei. Since it's from the same stratigraphic level and falls within the range of ontogenetic variation seen in L. lambei, there's really no reason not to consider it a synonym, at least provisionally. L. magnicristatus is generally considered distinct, but as pointed out by Evans and Reisz (2007), both known specimens come from a higher stratigraphic level than all other lambeosaurine species in the Dinosaur Park Formation, so it either completely replaced, or is a chronspecies of, the L. lambei. All of the potential older synonyms of Lambeosaurus, therefore, would become synonyms of Lambeosaurus lambei, specifically, and can't be considered nomina dubia.
Reconstruction of juvenile Didanodon altidens specimen
AMNH 5340 (previously Procheneosaurus praeceps)
by Matt Martyniuk, all rights reserved.

The other older synonym of Lambeosaurus lambei is Procheneosaurus praeceps, based on juvenile specimens that fit nicely into the known lambeosaurine growth series. Ontogeney is responsible for much of this taxonomic confusion, as juvenile lambeosaurines were originally thought to be adults of small-crested, small-bodied species known as "cheneosaurids" (Cheneosauridae is now a junior synonym of Hadrosauridae, and Cheneosaurinae of Lambeosaurinae).

It looks like Didanodon altidens is almost certainly the correct name for Lambeosaurus lambei. Can Lambeosaurus be saved? Only by petitioning the ICZN. This would certainly help tidy up the nomenclature and preserve a very widely used name. But here's where we all may have been retroactively lawyered by a previous ICZN decision from the early 20th century, also having to do with Procheneosaurus!
You see, as George Olshevsky has explained, Procheneosaurus was itself originally named, like Didanodon, without a type species in mind (in a photo caption, no less). The same juvenile lambeosaurine skeleton was later formally made the type specimen of Tetragonosaurus. This issue was brought before the IXZN to clarify, and they ruled that Procheneosaurus was valid, Tetragonosaurus was a junior objective synonym ,and as with all ICZN decisions, they added Procheneosaurus praeceps to the list of officially endorsed valid zoological names (ICZN Opinion 193). This may present a bigger problem than the dubious validity of Didanodon for poor old Lambeosaurus. It would be easy to have the ICZN officially suppress Didanodon altidens as a nomen rejectum (rejected name). But next in the line of priority is Procheneosaurus praeceps, which as we speak sits happily in the published lists of names with the ICZN stamp of approval.

Would the ICZN switch a name from a nomen conservandum (officially conserved name) to a nomen rejectum because a slightly newer name has since become very widely used? I don't know if there is precent for this or if there are any guidelines the ICZN would use to rule either way.

In other words, the only hope for the survival of our beloved Lambeosaurus is a good lawyer.

  • Osborne, H.F. (1902). "Distinctive characters of the mid-Cretaceous fauna." Contributions to Canadian Paleontology, vol. III. Part II, On the Vertebrata of the mid-Cretaceous of the North West Territory.
  • Lambe, L. (1902). "New genera and species from the Belly River Series (mid-Cretaceous)." Contributions to Canadian Paleontology, vol. III. Part II, On the Vertebrata of the mid-Cretaceous of the North West Territory.
  • Lund, E.K. and Gates, T.A. (2006). "A historical and biogeographical examination of hadrosaurian dinosaurs." Pp. 263- in Lucas, S.G. and Sullivan, R.M. (eds.), Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35.
  • Evans, D.C., and Reisz, R.R. (2007). "Anatomy and Relationships of Lambeosaurus magnicristatus, a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta." Journal of Vertebrate Paleontology, 27(2): 373-393.


  1. This is an excellent write up, and I agree with everything except the part where you imply that it matters - nomenclature exists to make science communication better, not to play gotcha with historical accidents. There is nothing but pedantry to support the idea of reversing a name that is almost as old and is the only one in common use, and if the ICZN won't make a ruling as such then frankly it should be ignored.

    Sorry, but science > lawyering.

    1. Although I should note that the ICZN has been pretty good about ruling in favor of names that are in current use (i.e. "doing its job"), so this probably ought to be dealt with formally in a petition.

    2. I've said it before, and I'll say it again, what if we just abandon the code? I just don't think there would be a problem with it - if a naming decision gets questioned in peer review, you justify it, or change it. Names work like our terminology for everything else. I believe this would err very much on the side of conservatism, which is what we want.

  2. Remember: we do not serve the Code; the Code serves us.

  3. I'm cool with Lambeosaurus being named for Lambe. He is one of the science's most under represented heroes for that era otherwise.

    I think the whole way we name organisms is outdated and stupid, and is part of why we're losing the science communication battle with the public. I'm a Dinosaur nut, and I can't pronounce many of the new age Dino names, and honestly it makes me care way less about these name animals. The name of something is powerful in public conscience. We should be looking at not only trying to capture people's interest with names, but using the powerful tools and research of marketing to capture people's interest (or at least understanding).

    For example I love how most Ceratopsians have a tops at the end of their name. I find they are overall easier to talk about with people, as they can get their head around the names.

    When Teratophoneus was announced some of my lay person coworkers (teachers) all noted what a stupid name it was (I didn't disagree for the record), and they immediately approached the whole thing with a negative attitude due to that reaction to the name. Palaeo hardcores might lift their nose to such ignorance (which I'm admit it is after a fashion, it is being intellectually lazy), but it is a warning sign. Sure people shouldn't judge a book by the cover (in this case the mere title), but we need to deal with the fact that they DO.

    I'd love to see a new nomenclature where there are fixed a part of the name that immediately told you what family or group an organism is in. Example tops at the end= ceratopsian. Something like a yrannus for Tyrannosaurs (Tyrannus Rex, Albertoyrannus, Tarboyrannus etc.)... same for everything from plants through beetle (oh how this would help everyone but entomologists!!! no more double naming anything with a pre-existing beetle's name)

    Is this madness? Definitely. Do I expect anyone to listen to me? No. However I can dare to dream. I can dare to dream.

    1. Hmm... it would work in an ideal world where taxonomist are almighty gods and know perfectly the systematic position of a fossil and fix it for the eternity... What if you name a new "-tyrannus" believing it was a tyrannosaurid and then a revision of its affinities show it belongs to another dinosaur group? It's a possible event, given how pervasive convergence is among dinosaurs.

    2. Tyrannus is preoccupied by an extant passerine bird.

    3. In fact, I would love Tyrannoraptora to be defined as the "Tyrannus + Tyrannosaurus" node.

    4. As long as we leave Raptor (a crustacean!) out of it.

  4. Scott and Tom expressed perfectly my thoughts.

  5. Thanks for the comments! For the record, I completely agree that the system should work for us, which is exactly why I'm against simply ignoring that system and letting nomenclatural gunk build up. There's no reason to simply pretend this situation doesn't exist, when it could be resolved by an iczn petition. Of course I'm also not advocating hadrosaur workers devote limited time and resources to this. That's why we used to have taxonomists, though that unfortunately seems to be a dying breed.

  6. There is no evidence that Didanodon altidens belongs to the same animal as Lambeosaurus. Both editions of the Dinosauria list Didanodon as a synonym of Lambeosaurus, but tabulate T. altidens as dubious. I had discussed the status of Didanodon with hadrosaur guru Alberto Prieto-Marquez and he says it's an indeterminate hadrosaurid (as is Trachodon selwyni).

    As a side note, the ICZN decision which suppressed Tetragonosaurus in favor of Procheneosaurus mistakenly assumed that Parks never designated a type species for Tetragonosaurus and failed to take into account the fact that the name Procheneosaurus was not accompanied by a description or the label "gen. nov." despite the fact that AMNH 5340 is accompanied by the label Procheneosaurus. So even if AMNH 5340 is Lambeosaurus, then it would make sense to list Procheneosaurus as a nomen nudum rather than a nomen oblitum because it was never accompanied by a description.

  7. Poor poor Matthew, you misunderstand how taxonomy works now days. Didanodon is fragmentary, so obviously it's a nomen dubium. And nomen nudum and nomen vanum are just the same thing- they mean we can ignore the name. Otherwise we'd have to do science to determine what Didanodon actually is, and that sounds hard. Much easier to only accept names based on relatively complete specimens, or make more complete neotypes for taxa we're used to that are based on fragmentary specimens.

    In all seriousness, this was a very interesting post. I didn't know about how the validity of conditionally proposed names changed through history. I wondered if this affected the most famous conditional dinosaur naming- Altispinax. This was done by Huene in 1926, so would be at a time when conditional proposals were allowed, contra Olshevsky . But looking over the details, Huene (1923) unconditionally proposed Altispinax as the genus for dunkeri years before the disputed conditional proposal, so the latter doesn't matter anyway.

    I do have to disagree with Scott, Tom and Andrea to say these things do matter. There seems to be an attitude these days that taxonomy is mere book-keeping that's below more organism-centric aspects such as ecology, ontogeny, behavior, etc.. But each is important in its own right. Sure taxonomy and law involve the application of human-created rules instead of the discovery of naturally occuring reality, but they both have real world implications. Just ask the Aetogate victims, or... anyone ever affected by laws. The ICZN was designed so that by serving it, it will serve us.

    1. "Much easier to only accept names based on relatively complete specimens"

      This is what really bugs me about the entire concept of nomina dubia. What qualifies as relatively complete? Presumably, things like Didanodon and Trachodon etc. are considered dubious because hadrosaurid teeth are not diagnostic to the generic or subfamilial level (I say presumably, are there any actual studies testing this?). But that's *now*, after we have good skeletons rather than just teeth. Many sauropods are diagnosed mainly based on vertebral characters. So as soon as we, inevitably, find that several biological species probably had verts identical to, say, Xenoposeidon, that name gets thrown out. What if we discover that different species or subspecies of Edmontosaurus can be diagnosed based on scalation pattern or distinct dorsal ridges? The type specimens which do not preserve skin get thrown out, and literally all saurolophines that lack scale impressions are suddenly "not complete enough", and we get new names for them all, which lasts just long enough for us to figure out what color they were. I predict Anchiornis huxleyi will be considered a nomen dubium within 10 years.

      This situation is why the idea of neotypes were invented. Nomina dubia should not exist. Deinodon horridus can no longer be diagnosed based on teeth alone because we've got these shiny complete skeletons with the same teeth but also all these more interesting characters? *Make that the neotype of Deinodon horridus*!

      Of course it's too late for all that now, and I like pointing these things out based on the slim chance it might motivate people to attempt suppression of the names and remove taxonomic clutter. It seems very likely that Anchiornis will be rendered potentially non-diagnostic based on soft tissue characters once somebody monographs a few of the hundreds of known specimens, since the holotype is fairly incomplete and lacks good feather preservation, let alone melanosomes. I hope that when that is done, the monographer will simultaneously petition the ICZN to make one of the better-known specimens a neotype. But I suspect they'll simply use the opportunity to coin a new name.

    2. I don't think there are any studies testing hadrosaur tooth variation. But this brings up an issue with your neotype solution.

      Iguanodon was originally based on teeth (I. anglicus), but Charig and Chapman (1998) asserted "the several known species of Iguanodon have no known features of the teeth by which they might be distinguished" and petitioned the ICZN to make I. bernissartensis the new type of the genus. This was at a time when (to quote Barrett from his comment to the ICZN) "An abundance of material has been referred to the genus Iguanodon, and the vast majority of this material clearly belongs to the same genus of iguanodontid ornithopod." But now we know what was thought of as Iguanodon is actually a polyphyletic array of taxa and that diagnostic ones like Hypselospinus and Barilium from the same sediments as I. anglicus aren't particularly close to I. bernissartensis. So Iguanodon has been stabilized as something different from what it was named for. Sues was prescient enough to foresee this in his ICZN comment, but was overruled- .

      If Deinodon horridus were to have a neotype, it would have ended up being Gorgosaurus or Albertosaurus, and either (or both) of these could be wrong. Or it could actually be indeterminate.

      But I do see the issue you bring up about more complete specimens making older species indeterminate, and I think I have a better solution than designating neotypes. As all of us except Wilson and Upchurch know, the ICZN doesn't care about nomen dubium status. So genera can have indeterminate type species, as long as the species is definitely in the genus. If Anchiornis huxleyi can't be distinguished from new distinct species A and B, just call A. huxleyi indeterminate but keep the new species in the valid genus Anchiornis. Since A. huxleyi is still definitely in Anchiornis, it won't matter even if we define an Anchiornithidae, just like Titanosaurus doesn't affect Titanosauridae.

    3. Regarding hadrosaur tooth variation:

      The recent paper by Erickson et al. on hadrosaur tooth structure was able to find some differences between the teeth of different hadrosaur clades (see supplementary figure S3 for the quick version). Conceivably, more study could parse finer divisions. The drawback is you might have to sacrifice some historical specimens.

      Erickson, G. M., Krick, B. A., Hamilton, M., Bourne, G. R., Norell, M. A., Lilleodden, E., and Sawyer, W. G. 2012. Complex dental structure and wear biomechanics in hadrosaurid dinosaurs. Science 338(6103):98-101. DOI: 10.1126/science.1224495

    4. I don't agree with you on the tooth thing. It's gotta be a pretty expressive tooth to work, to show diagnostic characters to makes any value of moving types without just "having a hunch", shrugging your shoulders, or making an overly broad argument that that tooth *probably* belongs to *that* skeleton. I've gone blue in the face talking about this on my blog, and few people pay attention, but it's important to note:

      A taxon based on a specimen, and ultimately to which the name should be rooted, is only as good as that specimen. Even were we in the desire to support and retain use of names from the past, if those names are based on crap, the name should go with it into the dustbins of history. If the name is tied to a better piece of crap, or something non-crappy, then we can make cases for its retention. And if the name has popular support, then -- THEN -- we can talk about moving names.

      It's not just dinosaurs. It's lizards, crocs, and fish; especially, sharks. It's mammals and nonmammalian theropsidans, with their fun teeth; it's especially about rodents, a billion of which are named based on partial dental series, mostly molars. It goes on. Step away from the peculiar chemistry of teeth that helps them preserve and you get shitty bone fragments, pieces of phalanges. And you get stuff prone to massive changes to shape during ontogeny. Which is why almost all names based on juvenile specimens of lambeosaur hadrosauroids should be chucked out the window.

      That said, note that Virginia Arbour and colleagues have been slowly dealing with the messy ankylosaurid situation in the Upper Cretaceous. Michael Ryan, Alberto Prieto-Marquéz on many hadrosauroids, David Norman and I guess Greg Paul on iguanodontoids, etc. Let the theropods wallow in relative misery until we can gain some understanding about the relative value of a scrap of bone, a share of tooth; then, maybe then, we can talk about working towards using types of terms of values of names, like "nomen dubium," and making them useful.

      My god, I had a post on the topic of nomina dubia and it was just a drop in the bucket of the stuff I've said on it. I've written posts about the decisions to ignore past taxonomic nomenclature to erect new species, and most of you've read them, but they gain no traction. This is just a thing that is "done," and you have to fight it at the source, at the entrenched teachers and schools who teach it's okay. Cut the head, and the body dies.

      Paleontology, like progress at UU, goes by way of dead mens' pointy shoes.

  8. [Quote] I suspect they'll simply use the opportunity to coin a new name.[/Quote]

    Sigh, I agree. Way to many paleontologists are making up new names for old clades and specimens, even when that entity already has a perfectly good name that has been in use for decades or even centuries. That's why I hate the 'crown group' definition of aves, that clade already has a name and the new definition ignores 100 years of aves being Archaeopteryx + Modern birds.

    So what if Velociraptor is then technically a 'bird' we no longer classify pronghorns as bovids. It would still be a dinosaur just like the pronghorn is still an Artiodactyl.

  9. Is it 100% established that hadrosaurs lacked cheeks?

    1. No, but there is also no compelling evidence so far that they had or even needed them. Good discussion at Jaime's blog here