Triceratops/Torosaurus - While a recent study suggests that these two dinosaurs are the same animal, these articles cannot be merged until a clear consensus exists in the scientific community. Please see WP:FRINGE and WP:UNDUE.
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Proposal to merge/redirect Tatankaceratops to Triceratops: Unlike the situation with other taxa (i.e. Torosaurus, Nedoceratops, Eotriceratops and Ojoceratops) where arguments for and against their validity have been made consistently (with all of these genera certainly being mentioned even in the 2024 study and included in various phylogenies), the validity of Tatankaceratops has not been supported by any subsequent study since it was first questioned by Longrich (2011), and not even included in any phylogenetic analysis ever since (addendum: except for one by Longrich (2014)). The genus name was last mentioned in studies published in 2017 and 2020: the former considered Tatankaceratops as an example of unwise holotype designation of immature specimens and an example of dubious or uncertain taxa, while the latter simply commented that they don't consider this genus valid in agreement with Longrich (2011). Even the 2012 study that supports the validity of Torosaurus considered Tatankaceratops uncertain, probably synonymous with Triceratops prorsus. Naish (2013) also considered this synonymy plausible, as characters are consistent with juvenile Triceratops. Overall, because no subsequent studies since Longrich (2011) ever considered this genus valid or included in any phylogenetic analysis, I propose that it is appropriate to merge/redirect Tatankaceratops to Triceratops. Junsik1223 (talk) 22:52, 26 February 2025 (UTC)[reply]
Is there consensus that Tatankaceratops can be assigned to Triceratops, or is it just an uncertain/dubious taxon? Seems that only Longrich has explicitly assigned it to Triceratops? --Jens Lallensack (talk) 23:21, 26 February 2025 (UTC)[reply]
So for the matter, we know Longrich has explicitly argued that Tatankaceratops is a juvenile Triceratops, and there hasn't been any rebuttal against this argument ever since (including the 2020 study which clearly stated that "Tatankaceratops, Ott and Larson, 2010, is not considered valid here, following Longrich, 2011."). It is more like Longrich made the argument first, and then pretty much everyone simply followed it. And Thomas Holtz did argue that he "STRONGLY suspect this is just a young Triceratops and not a distinct species." which can be considered an explicit argument. Junsik1223 (talk) 23:31, 26 February 2025 (UTC)[reply]
Also I'm pretty sure Geosternbergia was moved to Pteranodon sternbergi because of similar reasons (almost no researcher except one person continued to suggest the validity in that case) [1]; for Tatankaceratops, there was no one opposing it against Longrich (2011). Junsik1223 (talk) 23:38, 26 February 2025 (UTC)[reply]
Oppose for now, per IJReid, after a closer look. Longrich 2010 himself has only written a couple of sentences on the problem, stating that "this problem is beyond the scope of the present study", so I do not even see any formal assignment of this genus to Triceratops. Also, Naish (2013) takes an ambiguous view on this, contrary of what you state above. --Jens Lallensack (talk) 08:50, 27 February 2025 (UTC)[reply]
while I agree Darren Naish's stance wasn't really definitive, I considered it as a rough agree with potential need of revision (but I understand what you're saying); also maybe the 2015 thesis and Longrich (2014) I stated below would be a better argument? (since they at least state a reason or state that this seems likely and consistent with stratigraphy/phylogeny) Junsik1223 (talk) 12:13, 27 February 2025 (UTC)[reply]
We have to differentiate: If a taxon needs revision / is undiagnostic / is problematic, it is a Nomen dubium and must have its own article. Only if it is a synonym of a particular genus, then we should merge. So the question is "is there consensus that this is Triceratops and not something else"? Everything else (need of revision etc.) is irrelevant to this question. --Jens Lallensack (talk) 12:54, 27 February 2025 (UTC)[reply]
I think I weakly oppose by the logic of uncertainty if its diagnostic enough to refer to Triceratops. No studied other than Longrich 2011 has provided reasons for a synonymy, with most preferring an "indeterminate" designation, and even Longrich 2011 suggests that it may be a separate species and is uncertain. IJReid{{T - C - D - R}}02:57, 27 February 2025 (UTC)[reply]
For the latter argument though, it's not that Longrich (2011) considered it entirely separate, as he suggested it to be either a juvenile T. prorsus or dwarf form/species of Triceratops (which would still make it synonymous with Triceratops). Still I understand your stance. Junsik1223 (talk) 03:30, 27 February 2025 (UTC)[reply]
He doesn't take a very strong stance on its status, which is why I feel Longrich 2011 being cited as a reason for synonymy by other studies is equally not a very strong stance. IJReid{{T - C - D - R}}03:55, 27 February 2025 (UTC)[reply]
Just adding here that the 2015 thesis by John Benedetto Scannella, titled "Ontogenetic and stratigraphic cranial variation in the ceratopsid dinosaur Triceratops from the Hell Creek Formation, Montana", also supported that Tatankaceratops may represent T. prorsus based on the consistency with its stratigraphic position ("upper ( ~ 20 m below the K/Pg boundary) HCF in South Dakota"). Junsik1223 (talk) 04:18, 27 February 2025 (UTC)[reply]
And also just found that Tatankaceratops was once used in preliminary phylogenetic analysis by Longrich (2014) which showed the phylogenetic position of Tatankaceratops (along with Nedoceratops and Ojoceratops) within Triceratops spp., with Tatankaceratops recovered specifically as a sister taxon of T. prorsus (see supplementary material fig. s1); Based on these results, he stated that "The phylogenetic position of these three genera is consistent with referral to Triceratops and they were therefore excluded from further analyses." (For the record though, this proposal is just for Tatankaceratops only.) Junsik1223 (talk) 04:53, 27 February 2025 (UTC)[reply]
Oppose: Subsequent researchers suggesting that synonymity is "plausible" is insufficient to justify a merge in my opinion. Remarks like that are in papers all the time, and their presence should be included in articles, but not used to justify a merge. Furthermore, a taxon being "dubious" does not necessarily imply that it is a junior synonym. Plenty of dubious taxa do, and should, have their own articles (Dakotaraptor, Bagaraatan, Titanosaurus, etc). In the event that multiple authors publish explicit affirmative opinions that Tatankaceratops is a junior synonym of T. prorsus or Triceratops generally, then I think a case can be made for a merge. At this time, I think such a move is premature. A Cynical Idealist (talk) 01:38, 28 February 2025 (UTC)[reply]
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