Re: [dinosaur] Diplodocus status

There is of course a sliding scale of quality, but my point was that if you look at closely related species of theropods there are often only a few areas of the skeleton that have been proposed/demonstrated to differ. This is especially true for taxonomic splitters. So if multiple Tarbosaurus species are found to differ only postcranially, T. bataar's left in the cold. Or for Tyrannosaurus, afaik its type skull is only represented by maxilla, lacrimals, squamosal and ectopterygoid, so if species are based on differences in premaxilla, jugal, braincase, etc., or in postcrania the manus or the pes, the holotype would be specifically indeterminate. Ditto Archaeopteryx for manual characters or the external skull minus the snout tip and frontoparietal. These are all hypothetical obviously, but at least as likely as the counterfactual world Tim et al. are trying to stave off where contrary to every current expert's opinion, Diplodocus longus is found to be more closely related to Barosaurus, or outside the carnegii+lentus clade.

From: Gregory Paul <gsp1954@aol.com>
Sent: Thursday, October 15, 2020 7:00 PM
To: mickey_mortimer111@msn.com <mickey_mortimer111@msn.com>; dinosaur-l@usc.edu <dinosaur-l@usc.edu>; tijawi@gmail.com <tijawi@gmail.com>
Subject: Re: [dinosaur] Diplodocus status

The holotype of Tyrannosaurus is quite good, consisting of the majority of a skull and much of the skeleton with most of the diagnostic elements including pelvis, femur and even humerus, it being a robust from the upper Hell Creek (lacking the limb elements and its stratigraphy certain, 5027 is pretty useless and may well be a different species). It can be used to help determine whether there are multiple species of the genus in the region.

The holotype of Tarbosaurus is most of a very good and quite large adult skull, better than many if not most dinosaur type specimens.

The Archaeopteryx feather is inadequate, best the London specimen be the official type.

The Diplodocus holotype is very defective and no other specimens from the quarry help define what it was, prob would have been best to make D. carnegii the type.

GSPaul

-----Original Message-----
From: Mickey Mortimer <mickey_mortimer111@msn.com>
To: dinosaur-l@usc.edu <dinosaur-l@usc.edu>; Tim Williams <tijawi@gmail.com>
Sent: Thu, Oct 15, 2020 8:49 pm
Subject: Re: [dinosaur] Diplodocus status

As I said in my ICZN comment-

- There isn't even agreement that Diplodocus longus IS undiagnostic.
- Even IF Diplodocus longus was undiagnostic, undiagnostic species CAN be the type species of diagnostic genera. There's nothing in the ICZN arguing against that. That's a myth started by Wilson and Upchurch (2003).
- The argument about future-proofing for nomenclatural stability has zero urgency because all parties involved agree Diplodocus longus is definitely the same genus as D. carnegii, even the authors who petitioned the ICZN in the first place. Tim et al. would be arguing for an official nomenclatural change based on a case that nobody thinks is true or even likely.
- If we continue with this philosophy of designating the most complete species as the type species or the most complete specimen the neotype, there go the holotypes of Masiaksaurus, Majungasaurus, Marshosaurus, Acrocanthosaurus, Megaraptor, Albertosaurus, Tarbosaurus, Tyrannosaurus, Deinocheirus, Struthiomimus, Dromiceiomimus brevitertius and D. samueli, Suzhousaurus, Therizinosaurus, Incisivosaurus, Caudipteryx, Chirostenotes, Elmisaurus, Citipes, Avimimus, Conchoraptor, Anchiornis, Archaeopteryx, Microraptor, Saurornitholestes, Velociraptor, Deinonychus, Utahraptor, Sapeornis, Confuciusornis, Gobipteryx, Archaeorhynchus, Patagopteryx, Gansus, Ichthyornis, Baptornis and Hesperornis; and the type species of Alioramus, Tarbosaurus, Ornithomimus (as far as the lit is concerned), Archaeopteryx, Microraptor, Sapeornis, Confuciusornis and Gobipteryx (among Mesozoic theropods). It's a bad philosophy.

Mickey Mortimer

From: dinosaur-l-request@mymaillists.usc.edu <dinosaur-l-request@mymaillists.usc.edu> on behalf of Tim Williams <tijawi@gmail.com>
Sent: Thursday, October 15, 2020 4:27 PM
To: dinosaur-l@usc.edu <dinosaur-l@usc.edu>
Subject: Re: [dinosaur] Diplodocus status

I also thought _D. carnegii_ should replace _D. longus_ as the type species. So I disagreed with the ICZN decision.

Yes, I understand that, technically, a case could be made (and in fact was successfully made) that the _D. longus_ holotype is diagnostic - barely. But this is beside the point. For the sake of nomenclatural stability, and to 'future-proof' _Diplodocus_ as a valid genus, I thought the genus was infinitely better served in having _D. carnegii_ as the type species, rather than _D. longus_.

On Fri, Oct 16, 2020 at 6:28 AM Mike Taylor <sauropoda@gmail.com> wrote:
Yes, it's based on Diplodocus longus: the ICZN rejected a petition to change the type species to D. carnegii a couple of years ago. I submitted a comment in support; IIRC Mickey Mortimer submitted one against :-)

What does this mean? The petition was rejected partly on the grounds that the D. longus material was (wrongly in my opinion) considered sufficiently diagnostic, so the genus is OK. (I mean, by definition it's OK nomenclaturally, but it should be OK taxonomically.) But in practical terms, everyone who works on sauropods still means "kinda like D. carnegii" when they say "Diplodocus". No-one cares about the type material. So all that's happened is that the rejection of petition means that the nominal type species is not the same as the effective type species. If it ever turns out the D. carnegii is generically separated from D. longus, you can bet for sure that it will be carnegii that retains the name Diplodocus, whatever the ICZN may say.

-- Mike.

On Thu, 15 Oct 2020 at 20:14, Ethan Schoales <ethan.schoales@gmail.com> wrote:
What's the status of Diplodocus's type genus? Is it still D. longus, which is apparently dubious?

I hope Diplodocus doesn't end up as a dubious genus.