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Re: [dinosaur] Procheneosaurus



So after looking into this situation a bit, it's interesting but I think the ICZN made the correct decision. 

It has nothing at all to do with Lambeosaurus, as back in the 1920s-1940s cheneosaurs were seen as a valid group of small hadrosaurids with low crests (like aublysodontids vs. tyrannosaurs in the 1980s-1990s).  So in 1920, Procheneosaurus is named by Matthew based on those two sentences and without a species, but that was allowed before 1931, so it would be hypocritical to criticize Procheneosaurus for this and not a thousand other genera now viewed as valid (and an explicit type specimen and indication the author intended to create a new name weren't needed until 2000, so those are highly irrelevant).   In 1931, Tetragonosaurus preaceps was named by Parks based on what is even now (Evans, 2007) recognized as the same genus along with T. erectofrons.  In 1935 Lull was presumably writing what would be the highly influential Lull and Wright (1942) hadrosaurid monograph and asked the ICZN for a solution (as opposed to now where petitioners always have a stated desired outcome).  In 1936, the ICZN voted and decided that Procheneosaurus was valid, but hadn't dealt with Tetragonosaurus or species yet.

It's now 1942, Lull and Wright's monograph is published, and in it they state the ICZN's conclusion that "Procheneosaurus is, therefore, a perfectly definable genus and in no sense a nomen nudum."  What they do is make praeceps the type species of Procheneosaurus.  The ICZN writes Lull in 1943 and weirdly uses the monograph as evidence preaceps should be the type species of Procheneosaurus, while also using Article 13.3 ("every new genus-group name published after 1930 ... must, in addition to satisfying the provisions of Article 13.1, be accompanied by the fixation of a type species in the original publication [Art. 68] or be expressly proposed as a new replacement name (nomen novum) [Art. 67.8]") to declare Tetragonosaurus invalid.  This is all published by Hemming (1947) in BZN as Opinion 193.

So in a way Lull created the solution to his own problem, but I think it's the correct one for what was thought to be known at the time.  Jay's right that the original specimens of Procheneosaurus and praeceps are different, but they were viewed as conspecific at the time.  So if Lull would have given the 1920 Procheneosaurus based on AMNH 5340 a new species name, it would have immediately been sunk into praeceps and thus been both useless and defying Article 11.5 ("To be available, a name must be used as valid for a taxon when proposed").  This effectively gave Procheneosaurus a new type specimen, which I'm not a fan of but happens in Dinosauria (e.g. Stegosaurus, Coelophysis, Majungasaurus, Archaeopteryx).  And it is weird that there is no way AFAIK to designate a type species for a genus named after 1930 after the fact (but you can for genera named earlier), so this does invalidate Tetragonosaurus.  How do preaceps and erectofrons survive as valid then?  Well, for a species name "the generic name need not be valid or even available" (Article 11.9.3.1).  So the decision followed all the rules, didn't produce additional names, and got to honor both Matthew and Parks.

Of course now based on Evans' 2007 thesis and resulting publications, we assign both original Procheneosaurus AMNH 5340 and the praeceps type to Lambeosaurus sp. and the erectofrons type to Corythosaurus sp..  I've been in favor of indeterminate species within a genus, so hypothetically this would lead to Procheneosaurus praeceps (type, indet.), P. lambei, P. magnicristatus and P. indet. (AMNH 5340; former type of Procheneosaurus).  Dimirjian's petition was to "request to set aside Opinion 193 and remove Procheneosaurus Official List of Generic Names in Zoology, and Tetragonosaurus from the Official Index of Rejected and Invalid Generic Names in Zoology", which seems unnecessary.  Tetragonosaurus can remain invalid, and all that needs to happen is for Lambeosaurus to gain priority over Procheneosaurus.  The ICZN (2019) stated "Following discussion with the author, the Case is now closed", so I wonder what happened. 

Mickey Mortimer


From: dinosaur-l-request@mymaillists.usc.edu <dinosaur-l-request@mymaillists.usc.edu> on behalf of Justin Tweet <thescelosaurus@gmail.com>
Sent: Thursday, September 17, 2020 10:23 AM
To: dinosaur-l@usc.edu <dinosaur-l@usc.edu>
Subject: Re: [dinosaur] Procheneosaurus
 
Ah, yes, Procheneosaurus, based on two sentences, no type species, a type specimen by implication, and no indication that the author intended to create a new name. If this were 2020 instead of 1920, it would be another name in a museum exhibition guidebook, another "Xinghesaurus", but it was "named" before 1931, under much laxer rules, so it got by. The fact that the rules for pre-1931 names permitted it to be accepted is not an argument for Procheneosaurus, but an argument against the rules.-Justin

On Thu, Sep 17, 2020 at 11:24 AM Tyler Greenfield <tgreenfield999@gmail.com> wrote:
Procheneosaurus is certainly not a nomen nudum since it was conserved by ICZN Opinion 193. The type species of P. praeceps was fixed by that Opinion as well.

On Thu, Sep 17, 2020 at 7:19 AM jayp.nair@yahoo.com <jayp.nair@yahoo.com> wrote:
This would have been true, if Procheneosaurus Matthew 1920 was not a nomen nudum. This paper, a lay article on Canadian dinosaurs, lacks an adequate enough definition of what Procheneosaurus is, among other inadequacies. He literally only states: "(5) Procheneosaurus, – a small kind with a little bill and short round head. A fine skeleton is on exhibition in the American Musuem.". This appears inadequate as any diagnosis would go, and the text should not be taken as a diagnosis just to tick off on a taxonomic checkbox.

Also, it should be noted that the holotype of Tetragonosaurus praeceps Parks is a ROM specimen, and not that same specimen that Matthew was referring to in his article. A perusal of Parks' paper reveals no reference made to Matthew's 'Procheneosaurus' or to the American Museum specimen, so Tetragonosaurus shouldn't even be considered a replacement name for Procheneosaurus.

Given this second point, Procheneosaurus should be considered an invalid genus name, given it lacks a fixed type species (ICZN Art. 67.1).


On Thursday, 17 September 2020, 8:07:55 am AEST, Tyler Greenfield <tgreenfield999@gmail.com> wrote:


The conserved genus Procheneosaurus Matthew, 1920 has priority over Lambeosaurus Parks, 1923 if the two genera are considered synonymous. However, the subsequently designated type species of Procheneosaurus, Tetragonosaurus praeceps Parks, 1931, does not have priority over the type species of Lambeosaurus, Lambeosaurus lambei Parks, 1923. If the two species are considered synonymous, the correct combination would be Procheneosaurus lambei (Parks, 1923).

On Wed, Sep 16, 2020 at 4:33 PM Stephen Poropat <stephenfporopat@gmail.com> wrote:
Presumably because the type species of Procheneosaurus (Tetragonosaurus praeceps) was not named until eight years after Lambeosaurus lambei.

On Thu, 17 Sep 2020 at 07:09, Ethan Schoales <ethan.schoales@gmail.com> wrote:
It's an officially conserved name and it's older than Lambeosaurus, so why isn't it used?


--
Dr Stephen F. Poropat

Postdoctoral Researcher (Palaeontology)
Faculty of Science, Engineering and Technology
Swinburne University of Technology
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Hawthorn, Victoria
Australia 3122
Phone: +61 3 9214 5152
Alternate email: sporopat@swin.edu.au

Research Associate
Australian Age of Dinosaurs Museum of Natural History
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Winton, Queensland
Australia 4735


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Justin Tweet
Equatorial Minnesota, home of The Compact Thescelosaurus