Notable synonyms

[Sim]

The synonymy of Miragaia with Dacentrurus has got me thinking about something I think about sometimes: which animals should be synonyms?  I'll share my thoughts on below, feel free to add any you think of!

Albertosaurus: I can't tell Albertosaurus and Gorgosaurus apart.  I would like to keep them in separate genera, but they are so similar that I find it hard to justify.  Dan LoRusso told me that if the Battat Boston museum of science line had kept going, the fourth set would have included "Albertosaurus libratus"...  Gorgosaurus being considered a species of Albertosaurus has been happening for a long time.

Alioramus: The authors of Alioramus altai have accepted it is the same species as Alioramus remotus, which makes sense.  Qianzhousaurus has been suggested to be a species of Alioramus, perhaps even the adult of Alioramus remotus, but it isn't clear to me that this should be accepted.

Allosaurus: I find it suspicious that Saurophaganax is only known from the largest allosaurid skeletons found.  I suspect that Saurophaganax specimens are actually the oldest individuals of Allosaurus.  If they're not I believe they are insufficiently different to Allosaurus to be in a different genus.  I've seen Allosaurus jimmadseni and europaeus be synonymised with Allosaurus fragilis, but I believe that is over-lumping and that differences between them can be clearly seen.  Additionally, there is an upcoming paper that will describe postcranial difference between A. fragilis and A. jimmadseni.

Anchiornis: A study suggested that Aurornis is a junior synonym of Anchiornis, but Andrea Cau has shown that the two have very different pelvic structures.

Baryonyx: Considering Suchomimus as a species of Baryonyx hasn't been supported in the end.

Centrosaurus: The species "Coronosaurus brinkmani" and "Spinops sternbergorum" are repeatedly found to be the closest relatives of Centrosaurus apertus.  brinkmani was originally named as an additional Centrosaurus species and sternbergorum only differs from apertus in having longer hooks at the top of its frill.  I think it's ridiculous that these were given their own genus when they so closely resemble Centrosaurus apertus.  I'm following Gregory Paul on this, where these two are considered additional species of Centrosaurus.

Ceratosuchops: Sereno et al. considered Riparovenator a synonym of Ceratosuchops pointing out that there is similar difference between them as there is in Allosaurus fragilis specimens.  I prefer the name Riparovenator and would prefer that one being used instead of Ceratosuchops, for the record...

Chasmosaurus: There has recently been thought of splitting up Chasmosaurus, which I don't agree with.  I follow Gregory Paul's taxonomy for Chasmosaurus partially, I believe there are three species: the type C. belli, C. russelli and the long-horned C. perifania (aka Mojoceratops).  perifania is almost identical to russelli, I think it's absurd to put it into a different genus to russelli.  I don't agree with Vagaceratops being a species of Chasmosaurus, it looks quite different to belli, russelli and perifania and is sometimes recovered as closer to Kosmoceratops.

Cristatusaurus: Although I don't like it, it has been pointed out this species could be the senior synonym of Suchomimus tenerensis... by only a few months.

Coelophysis: The insulting name Megapnosaurus was given to a species, "Syntarsus" rhodesiensis, that looks almost identical to Coelophysis bauri.  Some have suggested Megapnosaurus should be used for rhodesiensis.  However as mentioned, it looks almost identical to C. bauri and keeping it in a different genus appears to be over-splitting to me.  If it means synonymising other genera with Coelophysis too, I see no problem with it, they all look very similar and no-one has a problem with Psittacosaurus having lots of species.  In contrast, the species "Syntarsus" kayentakatae is very different to bauri and rhodesiensis and as shown by phylogenetic analyses, it needs to be in a different genus.

Diabloceratops: Machairoceratops looks almost identical to Diabloceratops and is probably its descendant.  I think Machairoceratops could be made into an additional species of Diabloceratops.  I remember reading palaeontologist Michael Ryan suggesting that Machairoceratops is a synonym of Diabloceratops.

Dromiceiomimus: The species brevitertius and samueli, sometimes considered species of Ornithomimus, both have priority over the younger name edmontonicus, thus are the correct names to use over the latter.  These species are not closely related to the type species of Ornithomimus, O. velox, so placing them in Dromiceiomimus is appropriate.  The "Ornithomimus" specimens with feathers preserved are actually all Dromiceiomimus individuals as is described here: http://theropoddatabase.blogspot.com/2012/10/did-dromiceiomimus-really-have-long.html

Giganotosaurus: Tyrannotitan, Giganotosaurus, Meraxes and Mapusaurus all lived in the same area, one after the other.  They look basically identical, with Mapusaurus even being suggested to possibly represent the same species as Giganotosaurus carolinii.  I think all four of these could be considered species within the same genus, Giganotosaurus being the oldest and correct name for them in that case.  The presence of a sickle claw in Meraxes and possibly not in Tyrannotitan could be a reason to keep them separate, but it's presently unclear if this is a real difference L @Leyster has explained.

Herrerasaurus: Gnathovorax looks like a miniature Herrerasaurus, so I wonder why it was given its own genus?

Mantellisaurus: Dollodon which is considered a synonym of Mantellisaurus by a number of palaeontologists, is seen as a separate species by its namer, Gregory Paul.  Dollodon has different proportions to Mantellisaurus, but whether those are due to being different species I'm not sure anyone knows yet.

Nanosaurus: It is now agreed that there is only one very small Morrison ornithischian, Nanosaurus, with its syonyms including a number of names honouring the two Bone Wars rivals: Drinker, Othnielosaurus, Othnielia.

Ornithomimus: The silliest thing I've ever seen in palaeontology involves Ornithomimus, specifically the species "Ornithomimus edmontonicus".  People have been using it as the senior synonym of the species brevitertius, but as Mickey Mortimer of The Theropod Database has pointed out, brevitertius is the older name!  This has been recognised in a paper since.  However, use of "Ornithomimus edmontonicus" is still rampant.  It doesn't exist, people!  I will add that as Mortimer has pointed out, brevitertius is not closely related to the type species of Ornithomimus, O. velox, so placing it in the genus Dromiceiomimus is correct.  If you still want to place it in Ornithomimus, there's no getting around that brevitertius is an older name than edmontonicus, so using edmontonicus is objectively incorrect.  The species samueli is closely related to brevitertius, considering both different species of Dromiceiomimus is appropriate.

Pachycephalosaurus: The synonymy of Dracorex and Stygimoloch with Pachycephalosaurus has been accepted, and there are transitional forms to support the first two as forms of Pachycephalosaurus.

Pentaceratops: "Titanoceratops" fits into known ceratopsid growth stages as an old specimen of Pentaceratops.

Prenocephale: It was thought that all flat-headed pachycephalosaurians were juveniles of dome-headed adults, and that in the case of Prenocephale the flat-headed Homalocephale was most likely its junvenile.  However a juvenile Prenocephale has been found and it posesses a dome, showing that Homalocephale is not the juvenile form of Prenocephale.

Pteranodon: I read some editors on Wikipedia expressing regret about having created a page for Geosternbergia and that propelling that name into usage, as only Kellner used it and other pterosaur palaeontologists have kept using Pteranodon sternbergi.

Saichania: I used to think Tianzhenosaurus was a synonym of Saichania, but having seen a comparison of their skulls, I no longer think so.  They are almost the same size, with major differences.

Saurornithoides: Zanabazar, as cool as its name is, was originally named as a second species of Saurornithoides.  It tends to be recovered as the closest relative of Saurornithoides mongoliensis, so why not make it a species of that genus again?  Its skull looks basically identical to that of S. mongoliensis...

Sinraptor: Sinraptor hepingensis has been suggested to belong to a different genus to the nearly identical Sinraptor dongi, only due to some fragmentary species that don't make Sinraptor monophyletic.  I think it's unnecessary to split hepingensis from Sinraptor in this situation, it's clearly very closely related to dongi and fragmentary species can create some weird, probably artificial, results.

Spinosaurus: It's frustratingly unclear what the remains assigned to Spinosaurus represent, specifically if there's more than one species or genus involved.  I know there's more than one mouth and neck form in the Spinosaurus remains, but it's not yet clear which species which remains belong to...

Stegosaurus: Stegosaurus ungulatus has been said to be a synonym of Stegosaurus stenops by some, but I think that's unscientific as there are clear differences between the two which aren't known to be due to age or gender.  At the opposite extreme S. ungulatus has been split as a new genus by Gregory Paul.  I don't believe that is warranted and share the traditional opinion which is that S. ungulatus is an additional species of Stegosaurus.

Stenonychosaurus: It has been found that the giant troodontid Latenivenatrix is indistinguishable from Stenonychosaurus and is consequently a junior synonym of Stenonychosaurus.  This increases the known size of Stenonychosaurus.

Struthiomimus: The species sedens appears to belong in this genus instead of Ornithomimus.  Ornithomimus reconstructions tend to be based on Struthiomimus sedens (e.g. the Kaiyodo "Ornithomimus") or on Dromiceiomimus...

Tianyuraptor: A large specimen of Tianyuraptor was found and described in a paper that has received very little attention, presumably due to not being widely available.  This new specimen of Tianyuraptor has features of the holotypes of Tianyuraptor and Zhenyuanlong and it has been proposed Zhenyuanlong is a junior synonym of Tianyuraptor.

Triceratops: In the end it's been shown Torosaurus latus isn't a growth stage of Triceratops.

Tsaagan: I almost hate it, but Linheraptor is probably the same animal as Tsaagan, just a later growth stage.  The holotypes of Tsaagan and Linheraptor follow the ontogenetic development seen in other dromaeosaurids, e.g. Sinornithosaurus, where the snout becomes proportionally longer as the animal gets older.

Tyrannosaurus: There has been continued back-and-forth on whether Tarbosaurus is a species of Tyrannosaurus.  I used to believe they should be in separate genera due to different skull structure, with Tarbosaurus's leading it to have less binocular vision than Tyrannosaurus, as well as a different force distribution when it bit.  However, @thebermuda303 has linked to a page which shows that Tarbosaurus's skull is actually as wide as Tyrannosaurus's, the different skull structure being based on a crushed skull.  If that is true I feel like Tarbosaurus should be considered a species of Tyrannosaurus.  Whether Nanotyrannus is a juvenile Tyrannosaurus has proven highly controversial, and even at the end of all the debating I'm unsure what to think about it...  As for Tyrannosaurus imperator and Tyrannosaurus regina, I agree with the numerous palaeontologists that don't find these species supported well enough.

Velociraptor: Although Linheraptor and Tsaagan are almost indistinguishable from Velociraptor mongoliensis, they are not always found to be close relatives of Velociraptor...  It's surprising, but they have even been sometimes recovered as dromaeosaurines rather than velociraptorines like Velociraptor.  Keeping them separate from Velociraptor is the consensus.

Yangchuanosaurus: The consensus is that Yangchuanosaurus magnus is the adult of Yangchuanosaurus shangyouensis.

I'll add more as I have time!

[DefinitelyNOTDilo]

I will say, there is quite a bit more difference between giganotosaurines than ppl tend to think, it's more like albertosaurus/gorgosaurus/daspletosaurus than the various allosaurus species. As an example, Meraxes has an enlarged "sickle claw" on its innermost toe, whereas tyrannotitan has a standard carch foot, and Meraxes has a much more prominent sacral dip than its relatives.

I agree with the rest however, especially synonymising several of the various European spinosaurids, although while saurophaganax should def be synonymous with allosaurus, I'd say it warrants its own species as it has more differences with the other species in its skull than even jimmy and frag have with each other.

[Sim]

I actually find the differences between the Allosaurus species more noticeable than those between Albertosaurus and Gorgosaurus.  That's also a clue to what I will be saying about those two tyrannosaurids.

L @Leyster has said there is doubt that what has been identified as Tyrannotitan's second toe is actually the second toe.  If it is, I agree that is a significant difference that would warrant keeping Tyrannotitan and Meraxes in separate genera.  The dip in the back vertebrae is a difference between Meraxes and Giganotosaurus, but Tyrannotitan doesn't preserve that area and I don't know if Mapusaurus does.

As far as I'm aware, this is what Saurophaganax is known from, so I don't see much difference to Allosaurus...: https://www.deviantart.com/franz-josef73/art/Saurophaganax-2002-339842267

I've updated the entry for Giganotosaurus to mention the sickle claw thing, I've updated Allosaurus's with thoughts on there being only one species of this genus, and I've updated Ceratosuchops's entry to specify that the reason for synonymising it with Riparovenator is based on difference within one Allosaurus species.

[Sim]

I've added entries for Sinraptor, Yangchuanosaurus, Albertosaurus and Tyrannosaurus.  @thebermuda303, I'm unable to access the link you provided about the true skull width of Tarbosaurus, it would be helpful if it can be viewed again.

[Sim]

I've added a bit more for Tyrannosaurus, and I've added a new entry for Alioramus.  That's it for tonight!

[Primeval12]

I do hope Qianzhousaurus is its own genus... I also like Ceratosuchops as a name better personally. So how would it work for s junior synonym if the two animals were named in the same paper?

[DefinitelyNOTDilo]

As far as I'm aware, this is what Saurophaganax is known from, so I don't see much difference to Allosaurus...: https://www.deviantart.com/franz-josef73/art/Saurophaganax-2002-339842267

Here's a more updated look, you can see pretty significant differences especially around the top.

[Dinoguy2]

I would add Ingenia. Similar situation to Megapnosaurus. There was an ill-advised attempt at renaming it to Ajancingenia, but now most people consider it a synonym of Heyuannia.

[Sim]

Here's a more updated look, you can see pretty significant differences especially around the top.

I've found a skeletal that shows unknown parts too, and what is known of Saurophaganax's skull looks like that part in Allosaurus jimmadseni when comparing it to the image you posted?: https://www.deviantart.com/franoys/art/Allosaurus-Saurophaganax-maximus-skeletal-778663428

[Sim]

I do hope Qianzhousaurus is its own genus... I also like Ceratosuchops as a name better personally. So how would it work for s junior synonym if the two animals were named in the same paper?

I would prefer Qianzhousaurus being separate from Alioramus too, they look quite different and are from different formations.  If two synonymous animals are named in the same paper, I think which name gets used is up to personal preference and usually one gets chosen and other people follow in using the chosen name.  Spinosaurus maroccanus and Sigilmassasaurus are an example of this, they were named in the same paper and people have thought they are the same animal, Sigilmassasaurus being the name that's used.  If I'm remembering right, the same applies to Tyrannosaurus and Dynamosaurus, with Tyrannosaurus being the name that was chosen to be the valid one.  I think Ceratosuchops will be the name that wins, besides already being the one that was chosen by Sereno et al., the clade Ceratosuchopsini was named after it and it would be weird if it contained Riparovenator and not Ceratosuchops.

[Sim]

I've added entries for Dromiceiomimus, Ornithomimus and Struthiomimus!

[Sim]

I would add Ingenia. Similar situation to Megapnosaurus. There was an ill-advised attempt at renaming it to Ajancingenia, but now most people consider it a synonym of Heyuannia.

I'm not sure this one is notable enough..  Ajancingenia never got widespread use, unlike Megapnosaurus.  Outside of the ethical problem, this species never really receives attention.

[Sim]

I've added entries for Tianyuraptor, Tsaagan and Velociraptor!

[Sim]

I've added entries for Saurornithoides, Stenonychosaurus and Anchiornis!

[Sim]

I've added entries for Nanosaurus, Mantellisaurus, Pachycephalosaurus and Prenocephale!

[Dinoguy2]

I would add Ingenia. Similar situation to Megapnosaurus. There was an ill-advised attempt at renaming it to Ajancingenia, but now most people consider it a synonym of Heyuannia.

I'm not sure this one is notable enough..  Ajancingenia never got widespread use, unlike Megapnosaurus.  Outside of the ethical problem, this species never really receives attention.

That's true, I guess I was thinking about this topic in reverse - Ingenia was a very well-known name, which is no longer valid, so whatever it's current synonym is would be notable (as in people thinking "whatever happened to Ingenia?).

[Sim]

That's true, I guess I was thinking about this topic in reverse - Ingenia was a very well-known name, which is no longer valid, so whatever it's current synonym is would be notable (as in people thinking "whatever happened to Ingenia?).

I remember Ingenia but I never encountered it frequently, and if I'm not mistaken what it was well-known from included the holotype skull of Conchoraptor...  So it seems to me it was never notable..

[Sim]

I've added entries for Diabloceratops, Centrosaurus, Chasmosaurus, Triceratops and Pentaceratops!

[Dinoguy2]

That's true, I guess I was thinking about this topic in reverse - Ingenia was a very well-known name, which is no longer valid, so whatever it's current synonym is would be notable (as in people thinking "whatever happened to Ingenia?).

I remember Ingenia but I never encountered it frequently, and if I'm not mistaken what it was well-known from included the holotype skull of Conchoraptor...  So it seems to me it was never notable..

Maybe I'm just old, but I remember it popping up frequently in popular dinosaur books in the '90s. To the point it was treated as a pretty big deal when it was found to be preoccupied, especially with there being an entire subfamily named after it. *shrug*

[Sim]

I've added entries for Stegosaurus and Saichania!