In defense of Megapnosaurus

The coelophysid theropod Megapnosaurus rhodesiensis has had a complex nomenclatural history over its 50 years of existence. It was originally named Syntarsus rhodesiensis by Raath (1969), but this generic name was found to be preoccupied by the beetle Syntarsus asperulus. Ivie et al. (2001) subsequently erected Megapnosaurus as a replacement. This renaming proved to be controversial among paleontologists for three main reasons, as documented in a long thread on the Dinosaur Mailing List. First is that the authors are entomologists and the paper was published in an entomological journal. Second is that the etymology of the name (“big dead reptile”) was intended as a joke. Third is that it was alleged the authors neglected to contact Raath to get his input.

I find the first two complaints to be completely unwarranted. It is appropriate that Ivie et al., who discovered the homonymy and had previously published on the beetle Syntarsus, should get to choose the replacement name. The venue is likewise appropriate since it is a peer-reviewed journal focused on insect taxonomy, to which the preoccupation of Syntarsus is a relevant issue. Humorous names are not uncommon in zoological nomenclature nor are they usually considered problematic. As for the third complaint, Ivie clarified in a post on the DML that he had attempted to contact Raath but was unsuccessful. There were not any ethical violations in the naming of Megapnosaurus, and it conforms to the rules of the ICZN, so it is an available genus.

There is an alternate taxonomic scheme which instead considers rhodesiensis as a species of Coelophysis. Greg Paul was the first to lump Megapnosaurus into Coelophysis (Paul, 1988) and he continues to support this synonymy (Paul, 2016). Of course, Paul has become infamous for lumping genera without solid reasoning or consistency. This synonymy has been been advocated by Raath and others mainly to avoid using Megapnosaurus, which they consider to be unethically named (e.g. Bristowe & Raath, 2004). Even the Wikipedia page for rhodesiensis places it in Coelophysis [it has since been changed to Megapnosaurus]. However, there is a fair amount of evidence that Megapnosaurus is a distinct genus and not synonymous with Coelophysis.

Coelophysis hand 2

Manus of C. bauri (AMNH FARB 30631) in dorsal view, with the fifth metacarpal magnified. Modified from Barta et al. (2018).

Recent studies have clarified the anatomical characters that differ between Coelophysis and Megapnosaurus. One of the notable characters that distinguishes M. rhodesiensis is the lack of a vestigial fifth metacarpal, which is present in C. bauri (Barta et al. 2018). Other basal theropods like Eodromaeus and Dilophosaurus retain the fifth metacarpal, suggesting that M. rhodesiensis lost it independently of more derived theropods. Griffin (2018) identified four other characters unique to M. rhodesiensis: scar on the humerus for the origin of the m. triceps brachii caput mediale, shallow groove on the proximal surface of the femur, depression on the anterolateral face of the proximal portion of the femur, and anterolateral edge of the proximal surface of the femur extending anterolaterally. While these are ontogenetically variable in M. rhodesiensis, they are not found in any individuals of C. bauri regardless of age.

Coelophysidae phylogeny

Phylogenetic tree of the Coelophysidae after Ezcurra (2017), with Lucianovenator added after Martínez & Apaldetti (2017).

Aside from these characters, current phylogenetic analyses also support the separation of Megapnosaurus. The analysis of Ezcurra (2017) recovers M. rhodesiensis in a clade with Segisaurus and Camposaurus, while C. bauri is the sister taxon to Lepidus. Martínez & Apaldetti (2017) also place Lucianovenator in the clade with M. rhodesiensis. The oldest available name for this clade is Segisaurinae (Camp, 1936). Following this phylogeny, including only bauri and rhodesiensis in Coelophysis results in a polyphyletic genus. In order to have a monophyletic Coelophysis containing both bauri and rhodesiensis, Lepidus, Lucianovenator, Segisaurus, and Camposaurus would all have to be lumped into the genus. A genus spanning around 50 million years and distributed across three continents is not considered optimal in dinosaur taxonomy.

I recommend that the Paulian practice of lumping Megapnosaurus into Coelophysis be abandoned. There is sufficient anatomical and phylogenetic evidence that the two should be regarded as distinct genera in separate subfamilies. Synonymizing them would involve gratuitously lumping a number of other genera. Claims of Megapnosaurus being improperly or unethically named are misguided and there is no reason to suppress this name.

Addendum (8/2/2022)

McDavid & Bugos (2022) have just published their opinions on this matter. They support the use of Megapnosaurus for rhodesiensis instead of Coelophysis.

References

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7 thoughts on “In defense of Megapnosaurus

  1. As for the third complaint, Ivie clarified in a post on the DML that he had attempted to contact Raath but was unsuccessful.

    As I replied at the time, they had sent one letter to a white man in Zimbabwe during the late 1990s, when Mugabe was on his infamous roll. That was not a serious attempt to contact Raath in the sense of parts 2, 3 and 6 of the ICZN Code of Ethics. It was unethical incompetence on the part of the authors, the reviewers and (!) the editors.

    (It has even turned out that Raath was aware of the problem and was planning to publish a replacement name. He’s been scooped.)

    But as parts 1 and 7 make clear, and as I also mentioned at the time, none of this matters. The Code of Ethics is just a Recommendation, not an Article; whether a name conforms to it has no bearing on whether it is available. The genus name Megapnosaurus is thus available, end of story.

    Whether it’s also valid is a taxonomic, not a nomenclatural, decision. In other words, it’s a matter of splitting vs. lumping. There cannot be such a thing as “a fair amount of evidence that Megapnosaurus is a distinct genus and not synonymous with Coelophysis” as long as people don’t agree on a definition of “genus”; they don’t, and the ICZN doesn’t try to enforce any – it grants what is often called “taxonomic freedom” in Principle 1, up to and including not taking any stance on whether named taxa should even be monophyletic.

    “big dead reptile”

    “Big dead lizard”, rather. The Ancient Greeks didn’t have a concept of “reptile”.

    One of the notable characters that distinguishes M. rhodesiensis is the lack of a vestigial fifth metacarpal, which is present in C. bauri (Barta et al. 2018).

    I thought this was individual variation in C. bauri? If not, is it taphonomic variation?

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    1. As I replied at the time, they had sent one letter to a white man in Zimbabwe during the late 1990s, when Mugabe was on his infamous roll. That was not a serious attempt to contact Raath in the sense of parts 2, 3 and 6 of the ICZN Code of Ethics. It was unethical incompetence on the part of the authors, the reviewers and (!) the editors.

      Is it possible that Ivie et al. were not aware of the political situation in Zimbabwe at the time and thus unaware of the difficulty in contacting Raath via mail?

      (It has even turned out that Raath was aware of the problem and was planning to publish a replacement name. He’s been scooped.)

      What took him so long then? Proposing a replacement name requires little writing (less even than this blog post) and shouldn’t take very long to finish and submit. I think the original authors are responsible for the scooping problem when they are aware of their homonymy but fail to take action (see also the situation with Barsbold and “Ingenia“).

      Whether it’s also valid is a taxonomic, not a nomenclatural, decision. In other words, it’s a matter of splitting vs. lumping. There cannot be such a thing as “a fair amount of evidence that Megapnosaurus is a distinct genus and not synonymous with Coelophysis” as long as people don’t agree on a definition of “genus”; they don’t, and the ICZN doesn’t try to enforce any – it grants what is often called “taxonomic freedom” in Principle 1, up to and including not taking any stance on whether named taxa should even be monophyletic.

      I concede your point on the”taxonomic vs. nomenclatural” issue, but I think the majority of dinosaur workers (besides Paul) can agree that lumping six genera that span three continents and over 50 million years is excessive. I also think the different characters highlighted here would be enough for most to consider generic separation.

      “Big dead lizard”, rather. The Ancient Greeks didn’t have a concept of “reptile”.

      Maybe I’m mistaken, but I thought the Greek concept of a saurian included turtles and crocodiles as well as true lizards, which would mean it refers to reptiles.

      I thought this was individual variation in C. bauri? If not, is it taphonomic variation?

      It seems to be individual variation within Coelophysis, as some articulated manus have them and some don’t. In Megapnosaurus none of the articulated manus have the fifth metacarpal. Given the large sample size I think it’s safe to say that this is a distinguishing feature between the two.

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  2. Sorry, but I completely disagree that the rejection of the name Megapnosaurus by theropod workers is unwarranted!

    I don’t care about it being published in an entomological journal and by entomologists, but on the other two counts I hold Ivie et al accountable. I remember when this whole discussion went on after the publication of the Ivie et al paper, and was in direct contact with Mike Raath about the issue. Ivie et al violated two articles of the ICZN Code of Ethics in claiming the name (see https://www.iczn.org/the-code/the-international-code-of-zoological-nomenclature/the-code-online/), and their posterior excuses are simply non-credible.

    Article 3 of the Code of Ethics states:
    “A zoologist should not publish a new replacement name (a nomen novum) or other substitute name for a junior homonym when the author of the latter is alive; that author should be informed of the homonymy and be allowed a reasonable time (at least a year) in which to establish a substitute name.”

    Mike Rate was very much alive in 2001 (to the best of my knowledge he still is), and he was actually made aware of the synonymy by another entomologist some time before the Ivie et al paper was published; indeed, he told me that he already had a short note in preparation proposing a replacement name (together with the other entomologist, whose name I forgot) when the Ivie et al paper came out. That Ivie claimed to have contacted Raath on the DML is clearly a poor excuse – Mike was well known in the community, basically every theropod worker could have given him the email, and he was still active, working at the same institution he had been for more than 30 years. It shouldn’t have been difficult finding and contacting him if you really wanted.

    Article 4 of the Code of Ethics states:
    “No author should propose a name that, to his or her knowledge or reasonable belief, would be likely to give offence on any grounds.”

    Two comments on this: You are right that humorous names are not uncommon in biology, but, not being from the field of research, the authors should at the very least have checked with somebody who is active in the field if the humorous name they proposed might be offensive to specialists. As you have seen in the reactions, it most certainly is – so this is a violation of the article 4. Second, from communications with colleagues at the time, I remember having heard that Ivie et al in private conversations admitted to have chosen this name to show their contempt for palaeontology, specifically vertebrate palaeontology, which I find deeply offensive.

    Thus, I for one will refuse to use the name Megapnosaurus, even if it means to accept a generic synonymy that I don’t really believe in – I am with you on that point.

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    1. Two comments on this: You are right that humorous names are not uncommon in biology, but, not being from the field of research, the authors should at the very least have checked with somebody who is active in the field if the humorous name they proposed might be offensive to specialists. As you have seen in the reactions, it most certainly is – so this is a violation of the article 4. Second, from communications with colleagues at the time, I remember having heard that Ivie et al in private conversations admitted to have chosen this name to show their contempt for palaeontology, specifically vertebrate palaeontology, which I find deeply offensive.

      Thus, I for one will refuse to use the name Megapnosaurus, even if it means to accept a generic synonymy that I don’t really believe in – I am with you on that point.

      I’ll be blunt here – I think letting personal feelings get in the way of taxonomy is petty. “Big dead reptile” is not obscene and it doesn’t target a specific individual, so I don’t find it offensive. I frankly think those that do should grow a thicker skin. Even if the anecdote is true that Ivie et al. intended it to be derisive (which I doubt), then you’ve given them exactly the reaction they wanted.

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    2. I think, taxonomic and phylogenetic accuracy is more important than personal feelings. For sharp issues there is the ICZN. Has anyone brought the Megapnosaurus-issue to the ICZN to find a binding decision? If not – why not?

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