Cetiosaurus nomenclature, redux — comments from Paul Barrett and Pete Galton

July 6, 2009

For those of you who care about such things, the new issue 66(2) of the Bulletin of Zoological Nomenclature contains two comments on our petition to the ICZN to fix Cetiosaurus oxoniensis as the type species of the historically important genus Cetiosaurus (Upchurch et al. 2009) — both of them supporting the proposal  (Barrett 2009 and Galton 2009).

Cetiosaurus oxoniensis dorsal vertebra in anterior, right lateral and posterior views.  From Upchurch and Martin (2002:fig 5)

Cetiosaurus oxoniensis dorsal vertebra in anterior, right lateral and posterior views. From Upchurch and Martin (2002:fig 5)

Paul Barrett wrote (in part):

Cetiosaurus was the first sauropod dinosaur to be scientifically described (Owen, 1841) and one of the earliest dinosaurs to be recognised: the taxon is clearly of historical importance and stabilising its taxonomy would represent an important contribution to dinosaur studies.
Cetiosaurus is not only a historically important taxon, but also one that has been used to specify other groups within Dinosauria, including Cetiosauridae. In addition, Ornithischia, one of the major dinosaur sub-groups, has been defined as all dinosaurs that are more closely related to Iguanodon than they are to Cetiosaurus (Norman et al., 2004).

(I’d completely missed that use of Cetiosaurus as an external specifier for Ornithischia, which I suppose just goes to show that I should pay more attention to the ornithischian literature.)

Pete Galton wrote (in part):

It should be noted that the “Monograph of the genus Cetiosaurus” by Owen (1875) is based almost entirely on the Bletchington Station material of C. oxoniensis (Owen even used Phillips’ figures!). Also, as noted by Galton & Knoll (2006), the family CETIOSAURIDAE Lydekker, 1888 is based on C. oxoniensis Phillips, 1871 because Lydekker (1888, p. 137) indicated it as being the type species of Cetiosaurus Owen.

More good arguments there for the conservation of prevalent usage by formally recognising C. oxoniensis.

Anyone else who has strong feelings on this subject, either way, should get them in writing to the Executive Secretary, ICZN., c/o Natural History Museum, Cromwell Road, London SW7 5BD, U.K. (e-mail: iczn@nhm.ac.uk).



7 Responses to “Cetiosaurus nomenclature, redux — comments from Paul Barrett and Pete Galton”

  1. Really the presence of Cetiosaurus as an external specifier for Ornithischia shouldn’t matter in the medius vs. oxoniensis issue. After all, medius is a saurischian too, so the definition would still hold. The same goes for any Saurischia, Sauropodomorpha or Sauropoda definitions based on medius. Cetiosauridae is a different story, of course.

  2. Mike Taylor Says:

    Surely you agree that it’s good for important clades to be anchored on adequate material? Check out this figure again: are you even 100% certain that it’s a saurischian?

  3. Vertebrat Says:

    Does it matter? We all know what Ornithischia means, and if the external anchor turned out to be, say, an ornithopod, I doubt many palaeontologists would declare Stegosaurus not to be ornithischian any more. They’d just fix the definition.

    Formal definitions usually follow existing informal ones: you don’t define Ornithischia unless you’ve already identified a bunch of material that you think forms a natural group. The formal definition is useful because it clarifies the boundaries of the informal one, but if it doesn’t match, the problem is not in the informal definition. Definitions can’t be wrong per se, but they can be inconsistent with their users’ intent, which is pretty much equivalent.

    (Wow, Safari’s built-in spellchecker knows “ornithopod”.)

  4. Paul Barrett Says:

    You’re missing the point – I am saying that as Cetiosaurus -has been- used as a specifier the stability of the genus as a whole is important in this respect (as well as in many others – this was just a small part of my response).

  5. Mike, I’m sure we agree clades should be anchored on adequate material, it’s just the definition of adequate we could disagree on. In the case of a specifier for Sauropoda, Sauropodomorpha/Theropoda or Saurischia/Ornithischia, all we have to do is be able to say the material is a member of the larger clade. Doesn’t matter if it’s Sauropoda indet., it would still get the job done. Am I 100% certain C. medius’ type series is a saurischian? Well, no since I don’t study most of the other clades a large Mesozoic reptilian vertebra could derive from.

    It’s certainly not an ornithopod, as it differs from Iguanodon as described by Norman (1980) in various ways, most obviously only the first one or two caudals of Iguanodon are wider than tall, and have more dorsally placed transverse processes than OUMNH J13693.

    As for other large ornithishians, ankylosaurs and stegosaurs don’t ever elongate their distal caudals as much as OUMNH J13702 as far as I know.

    So this leaves marine reptiles like plesiosaurs, mosasaurs and ichthyosaurs. Plesiosaurs and ichthyosaurs have shorter disk-like centra unlike the elongated mid caudal vertebrae of C. medius, right? And mosasaurs have procoelous vertebrae, correct?

    Don’t get me wrong, I agree Cetiosaurus should be changed to have oxoniensis as its type species instead, and that one of the reasons that is important is for stability of Cetiosauridae. I’m just saying it doesn’t matter as far as the definitions of those larger clades (Sauropoda, etc.) are concerned.

  6. […] noted this long ago, but back in July 2009 (more than a year ago!) Paul Barrett and Pete Galton both published comments in the BZN that were supportive of our petition. Posted by Mike Taylor Filed in Cetiosaurus, […]

  7. […] that petition to the Bulletin of Zoological Nomenclature; a few months after its publication, positive comments from Paul Barrett and Pete Galton […]

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