Talk:Rubeosaurus

Specimens

Copied from the Brachyceratops talk page: The way I read the new PLOS article is that only one of the juvenile specimens previously referred to Brachyceratops can safely be referred to Rubeosaurus, and it is not the holotype, USNM 7951, which figured in this article previously. About the holotype:

"As thoroughly explicated by Sampson et al. [29], the holotype (USNM 7951) and other specimens from the type quarry of Brachyceratops are juvenile centrosaurines. USNM 7951 exhibits an unfused nasal horncore, a feature concordant with juvenile status (Fig. 3A). Furthermore, the two well preserved partial parietals from the Brachyceratops quarry (USNM 7951 and 7950; Fig. 3B, C) are missing most of their caudal bars and do not display features that could be classified as incipient versions of the diagnostic epiparietal morphologies in the frills of adult Rubeosaurus, Einiosaurus, or Achelousaurus. Finally, no elements from the Brachyceratops quarry exhibit autapomorphies or a unique combination of characters by which the taxon could be diagnosed. Brachyceratops montanensis should therefore be considered a nomen dubium."

It appears that the only specimen of Brachyceratops that has been referred to Rubeosaurus in that paper is USNM 14765. Another specimen, MOR 492, is also referred to Rubeosaurus, but it does not seem to ever have been included in Brachyceratops. FunkMonk (talk) 20:07, 12 August 2011 (UTC)

I would agree with you. Perhaps it's also useful to point out that the referral of USNM 14765 to Rubeosaurus is based on the flimsiest of evidence: a new interpretation, contra that of the original describer Gilmore, of the heavily damaged right side of the frill which would imply that the frill of the specimen is asymmetrical with the much better preserved left side showing an abnormal condition as it lacks the single autapomorphy of Rubeosaurus, the inward pointing P3 spike! It is more parsimonious to conclude that the left side represents the real morphology, the right side is ambiguous due to damage and the specimen does not represent Rubeosaurus.--MWAK (talk) 05:04, 13 August 2011 (UTC)

• Now that Stellasaurus has been named, are our restorations of Rubeosaurus now chimaeras, or just Stellasaurus? FunkMonk (talk) 13:34, 29 April 2020 (UTC)

Chimeras, the parietal anatomy is that of ovatus. Related, should we consider a merge into Stryacosaurus? A recent paper considered it a synonym of albertensis, and this new paper retained it as a distinct species but within Styracosaurus. Lusotitan (Talk | Contributions) 00:02, 30 April 2020 (UTC)

I think a merge is in order, though wasn't one of the papers only in press? Though I wonder whether McDonald and Horner will have a response. FunkMonk (talk) 06:59, 30 April 2020 (UTC)

The NT drawing doesn't appear to have the Stellasaurus nasal horn, so if Rubeosaurus is ever considered valid (if other parts are assigned to it that show it to be more distinct), it could maybe be used to illustrate that... It seems bit wonky, though. FunkMonk (talk) 09:59, 30 April 2020 (UTC)

While not strictly a published response, McDonald has responded on Twitter[1] saying that he agrees with sinking ovatus back into Styracosaurus and restricting it to its holotype, for what it's worth DrawingDinosaurs (talk | contribs) 15:52, 30 April 2020 (UTC)

In that case, I think we could go right ahead with merging the info here into Styracosaurus and Stellasaurus... FunkMonk (talk) 16:07, 30 April 2020 (UTC)

I feel that this is a bit premature. Remember that there is no commonly accepted operational definition of the concept "genus". This means that it is in principle impossible to prove that a species is part of a genus. The authors state that Rubeosaurus "should" be referred to as S. ovatus because it is the sister species of S. albertensis. However, no such rule exists in the ICZN. Phylogenetic analyses find genera to be sister species all the time without it being argued that the junior names should no longer be used. The real motive of course is that MOR 492 was in 2010 referred to Rubeosaurus and that the authors want to emphasize the new status of the specimen as genoholotype of Stellasaurus, and the incorrectness of the referral, by again demoting Rubeosaurus to a species of another genus. However, the nomenclatural validity of Rubeosaurus is in no way dependent on the referral and creating a separate genus name would have been justified even without the existence of MOR 492, as it is a simple matter of choice.

Also, the authors' position is wholly incoherent. They argue that there is a anagenetic line from S. albertensis over Stellasaurus and Eniosaurus towards Achelousaurus. All these forms are then closer related to S. albertensis than to S. ovatus, making Styracosaurus paraphyletic unless they are all subsumed under Styracosaurus — or unless Rubeosaurus is kept separate!

As the majority position holds that Styracosaurus albertensis is a separate taxon from S. ovatus/Rubeosaurus, it is more or less mandatory under Summary Style that we also have separate articles. So a merge is uncalled for. Unless over the course of many years it should transpire that the name Rubeosaurus has completely fallen into disuse within the paleontological community, it is much more convenient, and less confusing for the reader, if the article is titled Rubeosaurus. This also prevents an incessant cycle of creation and destruction, activated whenever some analysis happens to find S. albertensis and S. ovatus to be sister species or not.--MWAK (talk) 10:13, 3 May 2020 (UTC)

Maybe premature now, but since McDonald agreed to the synonymy, and one study went as far as considering S. ovatus a synonym of S. albertensis[2] (which would make the anagenesis sequence more clear cut), it would seem to be inevitable down the line? FunkMonk (talk) 10:26, 3 May 2020 (UTC)

I think you are letting your personal opinions get in the way, MWAK. What matters is what the literature says on the issue, and it is saying that it should not be treated as a distinct genus. It does not matter if a genus is a solidified concept, it matters that it is being called Styracosaurus. As far as my opinion goes, I see no issue with a paraphyletic Styracosaurus - what use is there for monophyly when they are all chronospecies anyways? Works for Australopithecus. If it were up to me Stellasaurus and Einiosaurus would be subsumed into the genus. Anyways, maybe we could keep a separate article but have it under the name Styracosaurus ovatus, as a compromise? Similar to the Edmontosaurus annectens or Dimetrodon borealis situations.Lusotitan (Talk | Contributions) 22:01, 3 May 2020 (UTC)

Depends on whether even ovatus survives synonymy, though. That study I linked apparently considers it to fall within he variation within Styracosaurus albertensis, as far as I could gather (we don't know whether this will become consensus, of course). And it's a pretty interesting study, hasn't gotten much attention, but it shows that it may be pointless basing genera on tiny differences in frill morphology, since single specimens can show asymmetry in the frills that would be enough to declare each half of the frill a distinct species if not found together. FunkMonk (talk) 22:12, 3 May 2020 (UTC)

Right, that complication slipped my mind. I rescind the idea. Lusotitan (Talk | Contributions) 22:19, 3 May 2020 (UTC)

Well, "the" literature does not reject the name Rubeosaurus: one scientific article does. This does not meet the criteria for WP:Common name. That very article sees monophyly as a decisive argument for sinking Rubeosaurus into Styracosaurus — but then is inconsistent by implicitly accepting a paraphyletic Styracosaurus. As it is conceivable that such gross logical errors will be noticed by other scientists, a future acceptance of the sinking should not be assumed.

Of course, if S. ovatus would be generally considered to be a junior synonym of S. albertensis, the articles should be merged. But this is indeed not the present consensus. The 2020 article rejects a synonymy at the species level.

So presently, we cannot safely predict whether the two taxa will be proven to be identical or whether Rubeosaurus will remain the more "common" name in (popular) science. It could well be that for many years, far more people will search for the meaning of Rubeosaurus than of S. ovatus. The present situation implies that under the Wikipedia policy there should be two articles, one of them named Rubeosaurus.--MWAK (talk) 10:33, 4 May 2020 (UTC)

It could be nice to see how this plays out either way. In any case, the Styracosaurus article needs to be updated as well... FunkMonk (talk) 18:37, 4 May 2020 (UTC)

Two scientific articles, actually. The two most relevant articles in recent memory about the given taxa, I may note. Not to mention the guy who coined Rubeosaurus said he concurs with the sinking proposed. I would say this is sufficient grounds to follow for now. Lusotitan (Talk | Contributions) 06:10, 5 May 2020 (UTC)

But those two articles do not defend the same position. Attempting to show, empirically, that Rubeosaurus is a junior synonym is fundamentally different from rejecting the name because of an adherence to a protoscientific genus concept :o). Of course, it might well be that McDonald's authority will sway others, but again, that should not be assumed but reacted on if it happens.--MWAK (talk) 15:26, 5 May 2020 (UTC)

As a middle ground at this point, the article could always be moved to Styracosaurus ovatus, a similar situation to what we have with Coelophysis rhodesiensis and Edmontosaurus annectens in a sort of limbo state until further publications either revive it or sink it more definitively. In the meantime the article for Styracosaurus should certainly be expanded to include the new information. IJReid ^{{{T - C - D - R}}} 19:04, 5 May 2020 (UTC)

Probably the best for now, I just saw there's an abstract supporting genus synonymy but a distinct S. ovatus in the latest Canadian Society of Vertebrate Palaeontology abstracts book.[3] Since S. ovatus is just a partial frill, not much distinct can be said about it (unlike those species you linked), so I'd support a full merge into Styracosaurus down the line, with all relevant info of course added there. FunkMonk (talk) 19:12, 5 May 2020 (UTC)

That abstract is from the same three authors who said the exact same thing in their Stellasaurus paper. Lusotitan (Talk | Contributions) 19:15, 5 May 2020 (UTC)

If MWAK accepts a preliminary page move, I believe an admin would be required since the target article already exists as a redirect. IJReid ^{{{T - C - D - R}}} 22:12, 5 May 2020 (UTC)

Yes, Rubeosaurus is just a frill. But it is by their frills that centrosaurines are distinguished! UALVP 55900 is a highly interesting fossil. However, its asymmetry does not show that the phylogenetic signal of the epoccipitalia is swamped by individual variation because it is clearly pathological. The fact that the P3 of its right side is slightly curved medially, does not convincingly show that the much stronger medial direction in Rubeosaurus is not species-specific. One only has to introduce the additional trait "degree of rotation relative to the skull midline" and it is no longer true that "the proposed diagnostic characters of Rubeosaurus ovatus fall within the range of asymmetry and intraspecific anatomical variation documented for Styracosaurus albertensis". Regardless, the 2020 paper offers stratigraphic and evolutionary arguments for its being a separate taxon.

Certainly, we cannot combine the line of reasoning of the two papers. Applying the criteria of anagenesis and variation simultaneously would result in us having to merge Stellasaurus (probably not valid by Holmes' standards anyway), Einiosaurus and Achelousaurus into Styracosaurus as well. The exact title of the article is not all that relevant but I strongly advise not to merge.--MWAK (talk) 21:51, 7 May 2020 (UTC)

Speaking of the anagenesis hypothesis, I guess the "taxon A" of Horner is now actually Stellasaurus, not R./S. ovatus (as we wrote in the Achelousaurus article)? FunkMonk (talk) 22:00, 7 May 2020 (UTC)

This is more or less true.--MWAK (talk) 06:01, 8 May 2020 (UTC)

• Yikes, here's yet another paper questioning whether S. ovatus is diagnostic:[4] What's with all the Styracosaurus papers lately? It concludes: "This supports the argument (Holmes et al. 2020) that Styracosaurus ovatus simply represents an extreme morph of S. albertensis, and is not a distinct taxon. At the very least, the diagnosis of S.ovatus is problematic and cannot rely solely on P3 processes that project posteromedially". A merge is probably still premature, but if there is no dissenting papers coming out, I guess it will be in order. FunkMonk (talk) 23:11, 11 May 2020 (UTC)

I think a merge is definitely in order at this point. Lusotitan (Talk | Contributions) 23:01, 12 May 2020 (UTC)

I wonder why they didn't just consider it a nomen dubium? Its frill isn't that different from that of Stellasaurus either? FunkMonk (talk) 12:42, 15 June 2020 (UTC)

The diagnosis for Stellasauurs includes "partially elongate P4 processes (spikes) less than half as long as P3", which is clearly not the case in the ovatus holotype. Lusotitan (Talk | Contributions) 18:13, 15 June 2020 (UTC)

Yeah, but since they vary a lot in Styracosaurus and within other genera, I'm sure they would vary in Stellasaurus too. Anyhow, many more specimens would be needed to test this. FunkMonk (talk) 18:15, 15 June 2020 (UTC)

Though the parietal anatomy varies a lot, the proportional length of the p3 and p4 does not vary to this extreme extent. It's the main distinguishing trait between Styracosaurus and Stellasaurus. Lusotitan (Talk | Contributions) 18:52, 15 June 2020 (UTC)

Merger discussion

Please see the formal merger discussion at the target source page. Discuss and agree to "merge" or "no merge" at that page. Thanks. GenQuest ^"scribble" 23:13, 8 February 2021 (UTC)