The Genus Question — Impact of New Archosaurian Binomina

So, what exactly would happen if — as I suggested both here and mentioned in the comments here — we went down that slippery slope, and distinguished all species as their own unique, equivalent taxa? How many new “genus”-like names would we coin (calling them “praenomina”) so as to consider all species equivalent?

If we started with something popular and “near and dear,” we can do this with Dinosauria, and even extend that outwards to Pterosauria and fossil Crurotarsi. The number of species which are not actual type species (under the Linnaean System) in Dinosauria alone is not high. I combed through a few resources (Paleobiology Database, Wikipedia, and my own records) in order to evaluate valid non-type species for three Archosaurian subgroups — Crurotarsi (Pseudosuchia), Pterosauria, and Dinosauria — with the intention of finding out a gross, by-the-numbers perspective on the impact of treating all non-type species referred to various “genera” as binomina themselves (or, in Linnaean-speak, by raising each of these species to “genus” rank, thus coining a new “genus” for each one).

Taxa not considered synonymous with another species, but which aren’t type species:

Crurotarsi (excluding eusuchians)
Paleorhinus ehlersi
Paleorhinus neukami [Ebrachosuchus]
Paleorhinus sawini
Paleorhinus arenaceus
Palaeoctonus aulacodus
Palaeoctonus dumblianus
Palaeoctonus orthodon
Smilosuchus adamanensis
Smilosuchus lithodendrorum
?Machaeroprosopus jablonskae
?Machaeroprosopus lottorum
?Machaeroprosopus maccauleyi
?Machaeroprosopus pristinus
?Machaeroprosopus reseri
?Machaeroprosopus rineharti
?Angistorhinus talainti
Phytosaurus cubicodon
Phytosaurus doughtyi
Phytosaurus scolopax
Leptosuchus imperfecta
Leptosuchus studeri
Aetosaurus arcuatus
Aetosaurus crassicauda
Stagonolepis olenkae
Typothorax antiquum
Desmatosuchus haplocerus
Desmatosuchus smalli
Postosuchus allisonae
Popsaurus langstoni [Lythrosuchus]
Protosuchus haughtoni [Lesothosuchus]
Protosuchus micmac
Shantungosuchus hangjinensis
Shantungosuchus brachycephalus
Sichuanosuchus shuhanensis
Nominosuchus arcanus
Hsisosuchus chowi
Hsisosuchus dashanpuensis
Steneosaurus bollensis
Steneosaurus leedsi
Steneosaurus edwardsi
Steneosaurus obtusidens
Metriorhynchus hastifer
Metriorhynchus superciliosus
Gracilineustes acutus
Cricosaurus suevicus
Cricosaurus saltillense
Cricosaurus vignaudi
Cricosaurus gracilis
Cricosaurus araucanensis
Cricosaurus schroederi
Cricosaurus macrospondylus
Suchodus brachyrhynchus
Purranisaurus casamiquelai
Geosaurus grandis
Geosaurus lapparenti
Dakosaurus andiniensis

Campylognathoides indicus
Campylognathoides liasicus
Dimorphodon weintraubi
Istiodactylus sinensis
Ctenochasma elegans
Ctenochasma tacqueti
Germanodactylus rhamphastinus [n1]
Nyctosaurus nanus
?Nyctosaurus bonneri
Pteranodon sternbergi [Geosternbergia]
Anhanguera blittersdorffi
Anhanguera fittoni
?Cearadactylus ligabuei
Coloborhynchus piscator
Ornithocheirus mesembrinus [Tropeognathus]
?Ornithocheirus bunzeli
Tupandactylus navigans [n2]
Sinopterus jii [Huaxiapterus]
Tupuxuara leonardii
Tupuxuara deliradamus

Psittacosaurus sinensis
Psittacosaurus meleyingensis
Psittacosaurus xinjiangensis
Psittacosaurus neimongoliensis
Psittacosaurus ordosensis
Psittacosaurus mazongshanensis
Psittacosaurus sibiricus
Psittacosaurus lujiatunensis [n3]
Psittacosaurus major
Psittacosaurus gobiensis
?Psittacosaurus sattayaraki [n4]
Thescelosaurus garbanii
Thescelosaurus assiniboiensis
Tenontosaurus dossi
Rhabdodon septimanicus
Zalmoxes shqiperorum
Dryosaurus lettowvorbecki [Dysalotosaurus]
?Probactrosaurus mazongshanensis
Gryposaurus monumentensis
Gryposaurus latidens
Brachylophosaurus goodwini [n5]
Saurolophus angustirostris
Prosaurolophus blackfeetensis
Parasaurolophus tubicen
Parasaurolophus cyrtocristatus
Hypacrosaurus stebingeri
Corythosaurus intermedius
Lambeosaurus magnicristatus
Lambeosaurus paucidens
?Stegoceras brevis
?Stegoceras edmontonensis
Sphaerotholus buchholtzae
Protoceratops hellenikorhinus
Centrosaurus brinkmani [n6]
Monoclonius ?lowei
Chasmosaurus russelli
Chasmosaurus ?kaiseni [n7]
Anchiceratops longirostris [n8]
?Torosaurus utahensis
Triceratops prorsus
?Lexovisaurus vetustus
Stegosaurus stenops
Stegosaurus sulcatus
Stegosaurus longispinus
Pinacosaurus mephistocephalus

Massospondylus kaalae
?Lufengosaurus magnus
?Yunnanosaurus robustus
?Cetiosaurus mogrebensis
Omeisaurus jungshiensis
Omeisaurus changshouensis
Omeisaurus fuxiensis
Omeisaurus tienfuensis
Omeisaurus luoquanensis
Omeisaurus maoianus
Omeisaurus jiaoi [n9]
Mamenchisaurus hochuanensis
Mamenchisaurus sinocanadorum
Mamenchisaurus youngi
Mamenchisaurus anyuensis
Mamenchisaurus jingyanensis [n10]
Rebbachisaurus tamesnensis
Dicraeosaurus sattleri
Apatosaurus excelsus [Brontosaurus] [n11]
Apatosaurus parvus [Elosaurus]
Apatosaurus louisae
?Apatosaurus minimus [n12]
Diplodocus carnegii
Diplodocus hayi
Diplodocus hallorum [Seismosaurus] [n13]
Camarasaurus grandis
Camarasaurus lentus [Morosaurus]
Camarasaurus lewisi [Cathetosaurus]
Brachiosaurus brancai [oh, wait, that’s Giraffatitan…] [n14]
Huanghetitan liujiaxiaensis
Pleurocoelus altus
Haplocanthosaurus delfsi
Neuquensaurus robustus

?Megapnosaurus kayentakatae
?Dilophosaurus sinensis [n15] (=? Sinosaurus triassicus)
?Ornithomimoides barasimlensis
?Megalosaurus cambrensis
Sinraptor hepingensis
Yangchuanosaurus zigongensis
Carcharodontosaurus iguidensis
?Allosaurus europaeus
Alioramus altai
?Dryptosaurus macropus
?Archaeornithomimus bissektensis
?Ornithomimus sedens
?Ornithomimus grandis
Dromeciomimus samueli
Nothronychus graffami
?Chilantaisaurus zhiziangensis [n16]
?Nanshiungosaurus bohlini
Caenagnathus sternbergi [n17]
Elmisaurus elegans [n17]
Unenlagia paynemili
Sinornithosaurus haoiana [n18]
Microraptor gui [n18]
Saurornitholestes robustus
Velociraptor osmolskae

Considering this list, 178 non-type species (excluding Avialae and Eusuchia) would require “praenomina,” of which 12 have already available names that can be coopted for use (although these taxa are not, like Brontosaurus excelsus, considered “valid” as equivalent to another “genus-species couplet,” like Apatosaurus ajax). This means, for 166 taxa, a new name would need to be coined. Now, mind, this excludes fossil birds, extant birds and crocs, fossil near-extant crocs (including mostly forms that resemble modern crocodilians). 97 of these are dinosaurs (and of those 7 which have names, 6 are sauropods), which means 54% of the noted taxa are dinosaurs. This implies that the bulk of taxa are dinosaurian, which already bear a significant upswing in modern taxonomy for getting a full binomen upon description, rather than being described as a new species to an already-established “genus.” These species represent significantly less than half of the total species described for the groups I’ve combed them from, implying that they will, while inflating the taxon list in accordance with other binomina, not change the actual diversity of species one whit. You end up only getting less species being described under the umbrella of some other taxon (“genus,” followed by type species, then discussion of other species).

As a further consideration, I have also excluded several species which are based solely upon teeth (which in Dinosauria total about 100 different taxa, and of those about 30% are non-type species — I’m estimating, as I must reconstruct my tooth-based taxon database). Tooth-based taxa are excluded largely because it is more or less impossible to evaluate them in comparison with regard to complete-dentition sets, heterodonty, etc.

Of the remaining taxa, the lion’s share belong to parasuchian and aetosaurian stem crocodilians. These taxa are largely used as index species for Triassic biostratigraphy, and as such removing some of these forms may upset various index zones in which their species are found. One must ask, then, whether naming these non-type species as new “genera” will effect the established usefulness of these “paleofaunas,” or if their use is actually all that, well … useful?

The number of taxa noted here (105 for dinosaurs, out of potentially 1000 non-avialaean dinosaurs), represents only 10% of the taxa presented, meaning that the impact of these forms is limited, whether they are “elevated” to “generic” level — or, in this consideration, are established as equivalent, producing a potential 10% increase in equivalent species. The additional benefits also include being able to treat each taxon as equivalent, thus permitting more access to various species rather than conflating additional species into their parent “genera” when only considering the type species. Each species would merely be the name listed on the analysis, rather than having to make inferences on which precise combination of species would be used.

I caution that this process should be restricted to fossil taxa of high profile groups. It is further useful to extent this philosophical approach to taxonomy and nomenclature by treating all fossil taxa this way, and then even further by treating all living taxa this way. The latter point would be far more radical, for rather than inflating by 5-10% of the “equivalent” taxa, it would likely inflate the number by 5000% (or more), considering the number of multi-specific “genera” within taxon groups such as Coleoptera, Bacteria, and the little issue of what to do with “subspecies.”

One hurdle at a time.

Update:  Turner et al. (2012) have just published an extensive reanalysis of Dromaeosauridae, and general systematics of Paraves in connection to this. In this analysis, they recognize fewer members of Dromaeosauridae (including Unenlagiidae, as “Unenlagiinae” — see here; Microraptoria, as “Microraptorinae” — see here; and Eudromaeosauria, which includes Velociraptorinae and Dromaeosaurinae), by recognizing that NGMC 91, “Dave“, is a juvenile of Sinornithosaurus millennii, and that Sinornithosaurus haoiana (Liu et al., 2004) is a junior synonym; similarly, Microraptor gui was sunk into Microraptor zhaoianus, on the basis of lack of consistency of putative autapomorphies: some specimens have it, some don’t, and some specimens of zhaoianus could also have it, or it varies among species. These names will be struck out above.

[n1] The name “Daitingopterus” has been mentioned in connection to this species, but only as an undefined term in Maisch et al. (2004), where it is a nomen nudum.
[n2] Ingridia was a name that was applied to a series of species formerly within Tapejara, imperator and navigans. However, when originally used by Unwin & Martill (2007), they designated the type species as imperator. Kellner & Campos (2007) had, earlier, also used imperator as the type species to Tupandactylus, and by the margin of time, theirs is the used name, and Ingridia (as useful it might be now for, say, navigans) is subsumed.
[n3] Recently, Hedrick & Dodson revised the taxonomy of the Lujiatun psittacosaurids and concluded that Psittacosaurus lujiatunensis, major, and Hongshanosaurus hui represented the same, ontogenetically variable species. Problematically, Hedrick & Dodson referred to these species as “Psittacosaurus lujiatunensis,” subsuming the earlier-named hui into lujiatunensis, which in the ICZN’s view is a no-no. The correct nomenclature, taking their referral for granted, would be Psittacosaurus hui for all three. However, this raises the additional specter of a new potential praenomen availble for “hui/lujiatunensis,” and so these names cannot be struck from the list as yet.
[n4] Named as a distinct, basal, and small form of Psittacosaurus by Buffetaut & Suteethorn (1992), it has recently been doubted to actually belong to Psittacosaurus, especially by Sereno (2010). It is, apparently, a ceratopsian of low maturity, and thus may not be diagnostic (Sereno, 2010), although age alone does not appear a consistent delimiter of diagnostic value.
[n5] Horner named Brachylophosaurus goodwini in 1988, but has since designated this species as a synonym of Brachylophosaurus canadensis (Horner et al., 2004).
[n6] While designating a new ceratopsian, Xenoceratops foremostensis, Ryan et al. (2012) has designated brinkmani to its own “genus,” Coronosaurus.
[n7] Determined by Longrich (2010) to be nondiagnostic with respect to either Chasmosaurus or Pentaceratops, while also remarking that various features of the frill place this form close to Pentaceratops sternbergi (rather than within Chasmosaurus); he further considered that the material is also consistent with his new taxon, Mojoceratops perifania, along with Eoceratops canadensis, but refrained for synonymizing them. There are difficulties with this, including designation of “nomina dubia” runs into problems when you can also determine it is synonymous with another species, but further than these two taxa have names older than Mojoceratops perifania, in which case priority would seem to designate Eoceratops canadensis as the correct name, designated by Lambe in 1914 (as Chasmosaurus canadensis) and 1915 (as Eoceratops canadensis).
[n8] Mallon et al. (2011) has argued, through extensive sampling, that Anchiceratops longirostris represents variation in Anchiceratops ornatus.
[n9-10] The entire complex of species referred to Omeisaurus and Mamenchisaurus represent, for the most part, single skeletons. No systematic analysis analyzing variation among the skeletons has yet been produced in sorting out what species, or specimens, belong to each of these containers. It is possible they represent a broad grade (or several grades) and may even represent individual variation of smaller sets of species.
[n11] Yeah, that’s right.
[n12] Currently in the process of being redescribed by Drs. Mike Taylor and Matt Wedel (of SV-POW!). A new “genus” may be designated for this.
[n13] Lovelace et al. (2007) differentiated Seimosaurus hallorum from Supersaurus vivianae, but determined that the variation appears to fall into variation between specimens referred (generally) to Diplodocus. While it seems that the complex of Diplodocus includes hallorum, Lovelace et al. (2007) also suggested hallorum could be referred to longus, but did not qualify this.
[n14] Yeah, that’s also right. Arguably, this is the argument I wish Mike Taylor had made in designating Paul’s (1988) “genus” valid, but c’est la vie.
[n15] This one has been in the works so long, it’s not funny anymore. sinensis has been more or less clearly distinguished from Dilophosaurus wetherilli (and in fact, most “coelophysoid” grade theropods) for the greater part of three decades, but systematic evaluation has languished.
Edit: As an additional note, this species has now been synonymized into Sinosaurus triassicus. I am reluctant to agree with this as the basis for the referral is the supposed similarity of a small fragement of bone and teeth.
[n16] The type species of Chilantaisaurus is tashuikouensis (Hu, 1964), and was redescribed by Benson & Xu (2008), then later as a “megaraptoran” (Benson et al., 2010); Hu also described Chilantaisaurus maortuensis, and this was later described as Shaochilong maortuensis as a carcharodontosaurid (Brusatte et al., 2009). “Chilantaisauruszheziangensis (Dong, 1974) has yet to be definitely assigned, but it appears to be a therizinosauroid (Barsbold & Maryańska, 1990) and thus quite, quite distinct from other species of Chilantaisaurus.
[n17] These species were assumed to be synonymous with each other by Varricchio (2001), but also in more convoluted arrangements, where Currie & Russell (1988) referred sternbergi to Chirostenotes pergracilis, and elegans as Chirostenotes elegans (while maintaining distinction with Elmisaurus rarus). I maintain (as I do here and here, and following Currie, 1990) that while probable, it is not currently possible to determine wether these two species represent the same form, especially given geographical and stratigraphic separation. Moreover, as Cracraft (1970) argues, sternbergi represents a distinctly different form from that of Caenagnathus collinsi, so if collinsi and pergracilis are synonymous, it represents a wholly distinct taxon, and this may be true for elegans as well, which differs from all pes morphologies referred to Chirostenotes pergracilis to date, and even to rarus.
[n18] referred by Turner et al. (2012) to their type species as variations on a theme.

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Benson R. B. J., Carrano, M. T. & Brusatte, S. L. 2010. A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic. Naturwissenschaften 97 (1): 71–78.
Benson, R. B. J. & Xu X. 2008. The anatomy and systematic position of the theropod dinosaur Chilantaisaurus tashuikouensis Hu, 1964 from the Early Cretaceous of Alanshan, People’s Republic of China. Geological Magazine 145 (6): 778-789.
Brusatte, S. L., Benson, R. B. J., Chure, D. J., Xu X., Sullivan C. & Hone, D. W. E. 2009. The first definitive carcharodontosaurid (Dinosauria: Theropod) from Asia and the delayed ascent of tyrannosaurids. Naturwissenschaften 96 (9): 1051-1058.
Buffetaut, E. & Suteethorn, V. 1992. A new species of the ornithischian dinosaur Psittacosaurus from the Early Cretaceous of Thailand. Palaeontology 35: 801-812.
Currie, P. J. 1990. The Elmisauridae. pp. 245-248 in Weishampel, Dodson & Osmolska (eds.) The Dinosauria. University of California Press (Berkeley).
Currie, P. J., Godfrey, S. J. & Nessov, L. A. 1994. New caenagnathid (Dinosauria: Theropoda) specimens from the Upper Cretaceous of North American and Asia. Canadian Journal of Earth Sciences – Revue canadienne de Sciences de la terre 30: 2255-2272.
Dong Z.-m. 1979. The Cretaceous dinosaur fossils in southern China. pp. 342-350 in (eds.) Mesozoic and Cenozoic Red Beds in Southern China. (Institue of Vertebrate Paleontology and Paleoanthropology, Nanjing Geological and Paleontological Institute of Sciences Press, Beijing.) [in Chinese]
Hedrick, B. P. & Dodson, P. 2013. Lujiatun psittacosaurids: Understanding individual and taphonomic variation using 3D geometric morphometrics. PLoS ONE 8 (8):e69265.
Horner, J. R. 1988. A new hadrosaur (Reptilia, Ornithischia) from the Upper Cretaceous Judith River Formation of Montana. Journal of Vertebrate Paleontology 8 (3): 314-321.
Horner, J. R., Weishampel, D. B. & Forster, C. A. 2004. Hadrosauridae. pp. 348-463 in Weishampel, Osmólska & Dodson (eds.) The Dinosauria (2nd edition). University of California Press (Berkeley).
Hu S.-y. 1964. Carnosaurian remains from Alashan, Inner Mongolia. Vertebrata PalAsiatica 8 (1): 42–63. [In Chinese, with English summary]
Kellner, A. W. A. & Campos, D. A. 2007. Short note on the ingroup relationships of the Tapejaridae (Pterosauria, Pterodactyloidea. Boletim do Museu Nacional 75: 1-14.
Lambe, L. 1914. On Gryposaurus notabilis, a new genus and species of trachodont dinosaur from the Belly River Formation of Alberta, with a description of the skull of Chasmosaurus belli. The Ottawa Naturalist 27 (11): 145-155.
Lambe, L. 1915. On Eoceratops canadensis, gen. nov., with remarks on other genera of Cretaceous horned dinosaurs. Canada Geological Survey, Museum Bulletin 12: 1-49.
Liu J.-y., Ji S.-‘a., Tang F. & Gao C.-l. 2004. A new species of dromaeosaurids from the Yixian Formation of western Liaoning. Geological Bulletin of China 23 (8): 778-789.
Longrich, N. R. 2010. Mojoceratops perifania, a new chasmosaurine ceratopsid from the Late Campanian of western Canada. Journal of Paleontology 84(4): 681-694.
Lovelace, D. M., Hartman, S. A. & Wahl, W. R. 2007. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu, Rio de Janeiro 65 (4): 527-544.
Maisch, M. W., Matzke, A. T. & Ge S. 2004. A new dsungaripteroid pterosaur from the Lower Cretaceous of the southern Junggar Basin, north-west China. Cretaceous Research 25 (5): 625-634.
Mallon, J. C., Holmes, R., Eberth, D. A., Ryan, M. J. & Anderson, J. S. 2011. Variation in the skull of Anchiceratops (Dinosauria, Ceratopsidae) from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta. Journal of Vertebrate Paleontology 31 (5): 1047-1071.
Paul, G. S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2: 1-14.
Ryan, M. J., Evans, D. C. & Shepherd, K. M. 2012. A new ceratopsid from the Foremost Formation (middle Campanian) of Alberta. Canadian Journal of Earth Sciences — Revue canadienne de sciences de la Terre 49 (4): 1251-1262.
Sereno, P. C. 2010. Taxonomy, cranial morphology, and relationships of parrot-beaked dinosaurs (Ceratopsia:Psittacosaurus). pp. 21-58 in Ryan, Chinnery-Allgeier & Eberth (eds.) New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Indiana University Press (Bloomington & Indianapolis).
Taylor, M. P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrate Paleontology 29 (3): 787-806.
Turner, A. H., Makovicky, P. M. & Norell, M. A. 2012. A review of dromaeosaurid systematics and paravian phylogeny. Bulletin of the American Museum of Natural History 371: 1-206. [PDF available directly here, but it is large.]
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Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42-57 in Tanke, Carpenter & Skrepnick (eds.) Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana University Press (Bloomington & Indianapolis).

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15 Responses to The Genus Question — Impact of New Archosaurian Binomina

  1. Vahe Demirjian says:

    Dacentrurus phillippsi and D. vetustus are new combinations for Omosaurus phillippsi Seeley, 1893 and O. vetustus von Huene, 1910, both of which are now considered Dinosauria indet. (Maidment et. al. 2008), Additionally, “Stegoceras” brevis is described as a new genus in the Ph.D thesis of Schott (2011), while “Stegoceras” edmontonense is treated as a nomen dubium referrable to cf. Sphaerotholus sp. by Williamson and Carr (2002). Lambeosaurus paucidens is a nomen dubium referrable to Lambeosaurinae indet. (Prieto-Marquez et. al. 2006), and Phytosaurus scolopax is a new combination for Belodon scolopax, a nomen dubium in Phytosauria (Ballew 1989).

    BALLEW, K. L. 1989. A phylogenetic analysis of Phytosauria from the Late Triassic of the western United States. 309–339. In LUCAS, S.G. and HUNT, A. P. (eds). Dawn of the age of dinosaurs in
    the American Southwest. New Mexico Museum of Natural History, Albuquerque, 414 pp.

    Prieto−Márquez, A., Weishampel D.B., and Horner J.R. 2006. The dinosaur Hadrosaurus foulkii, from the Campanian of the East Coast of North America, with a reevaluation of the genus. Acta Palaeontologica Polonica 51 (1): 77–98.

    Maidment, S. C. R., D. B. Norman, P. M. Barrett, and P. Upchurch. 2008. Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). Journal of Systematic Palaeontology 6:367–

    R.K. Schott, 2011. Ontogeny, diversity, and systematics of pachycephalosaur dinosaurs from the Belly River Group of Alberta. M.Sci. thesis, University of Toronto, 173 pp.

    • Thanks for the notes! The “genus” labels for the species included in the list are, for the most part, either the original, or latest, referrals to which I found data for on my casual search. I did not make a point of allocating these names to their “current” standards following explicit research, especially as I did not want to cite theses, unpublished manuscripts, or conference abstracts. The relevant portion — to me — is the species name, rather than the “genus” referral. I am, for the most part, ignoring subjective “nomen dubium” arguments as these tend to be judgement calls (e.g., Dyoplosaurus acutosquameus was an n.d. for most of its existence, but lately appears to be diagnostic; and how some works tend to be more prone to assign n.d. status because they chose some highly restrictive criteria for which a species may be “diagnostic”).

  2. “These taxa are largely used as index species for Triassic biostratigraphy, and as such removing some of these forms may upset various index zones in which their species are found. One must ask, then, whether naming these non-type species as new “genera” will effect the established usefulness of these “paleofaunas,” or if their use is actually all that, well … useful?”

    No. This is the one of the big reasons I support monospecific genera. If a paleofauna is based on a multi-species genus, knowing that genera are fake, it follows that the paleofauna is also fake (unless some additional studies are provided that show all the species in the genus are actually chonspecies or something; in fact, I’d support using the genus or a genus-like concept to encompass chronspecific lineages which can’t really be reflected well as clades).

    Yes, it’s perfectly reasonable to work around this issue by simply never using genera by themselves in this type of study. But in practice nobody does that, so it’s time to just force them to. Look at “Toroceratops” for example. A lot of the vagueness of that hypothesis would have had to be dealt with prominently upfront in the literature if only Triceratops prorsus and Torosaurus utahensis had been assigned to their own “genera” from the get-go.

  3. Of the theropods…
    kayentakatae probably needs its own genus, as it is not necessarily closer to rhodesiensis than to Segisaurus (Tykoski, 2005).
    rhodesiensis has it’s own genus- Megapnosaurus.
    barasimlensis is indeterminate and not necessarily Ornithomimoides, so you could have also listed all the non-Megalosaurus species and ~40 others too.
    hepingensis probably also needs its own genus, as it is seemingly not closest to dongi (Carrano et al., 2012).
    I’m increasingly thinking Allosaurus “jimmadsensi” is just fragilis and that the Zhou et al. (2000) Caudipteryx specimens are just C. zoui.
    As the Daspletosaurus species have not been named or even defended in the published literature, it seems premature to include them.
    Alioramus altai is probably a junior synonym of A. remotus, as Brusatte et al. (2012) all but admit.
    Dromiceiomimus samueli has a basically stratigraphic separation from D. brevitertius, with only three Dromiceiomimus specimens’ ulnohumeral ratios being a valid morphological difference (Database).
    sedens is probably not Ornithomimus but is valid, so you’d need to include Nanshiungosaurus? bohlini, “Chilantaisaurus” zheziangensis, “Archaeornithomimus” bissektensis, “Dryosaurus” grandis, “Labrosaurus” stechowi, “Dilophosaurus” sinensis and “Megalosaurus” cambrensis too. But as those already need new genus names, they don’t fit the point of your list.
    graffami may need its own genus, as only one of the proposed Nothronychus synapomorphies is valid (Database).
    I think it most probable Caenagnathus sternbergi is Elmisaurus elegans, though that is itself an example compared to E. rarus.
    paynemili may be synonymous with Neuquenraptor and/or Unenlagia comahuensis.
    Since we now know Microraptor has antorbital fossa pitting, haoiana may not be Sinornithosaurus after all. More work is needed.
    M. gui is near certainly just M. zhaoianus (Database).
    Saurornitholestes robustus is probably a case similar to barasimlensis (Turner, 2008).
    The grouping of osmolskae with mongoliensis has never been tested.

    To your list I would add…
    Possibly Ceratosaurus dentisulcatus and/or magnicornis.
    Yanchuanosaurus zigongensis (Carrano et al., 2012).
    Possibly Dryptosaurus macropus and Troodon bakkeri.
    And I’m assuming you skipped pygostylians.

    So for well supported examples- zigongensis, iguidiensis?, europeus?, elegans.
    Need further study to see if they count- dentisulcatus, magnicornis, macropus, bakkeri, haoiana, osmolskae.
    Poorly supported examples- samueli, graffami, paynemili.

    13 species.

    • Emended with some of these factors (haoiana was already on the list). Consider that I am excluding 1) tooth-based taxa, 2) following general arguments for referral (dentisulcatus and magnicornis = nasicornis), 3) ignoring arguments about most “nomina dubia.” As there is no explicit criterion for “3,” I am generally using a broad qualification: It gets included. This does have the caveat that many of these taxa should be analyzed in phylogenetic analysis, and their material evaluation for diagnostic criteria (in broad or strict senses). I am not making that judgement beforehand. I am also going to wait for systematic analyses before following the Theropod Database judgements, as we’ve discussed in some cases. Similarly, I will not presume synonymy without explicit overlap of material + morphology (as explained here).

    • Anonymous says:

      I was going to say pretty much the same thing, but Mickey beat me to it. The fact that “Dilophosaurus” sinensis needs a new genus is probably one of the worst-kept secrets in theropod paleontology, as I have yet to see a single analysis that assigns “D.” sinensis to Dilophosaurus without scare-quotes. I’ve seen some suggestion that Allosaurus europaeus is synonymous with fragilis, but I personally wouldn’t know enough to say for sure. Having seen the two purported species side-by-side, I do doubt the idea that “jimmadensi” and fragilis are synonymous based on some of their proportions, though the point is relatively moot until someone actually describes the specimens of the former and compares them to the latter. I think most people currently regard Haplocanthosaurus delfsi as a synonym of H. priscus, though I am unaware of any study formally synonymizing the two taxa. “Apatosaurus” minimus is currently being redescribed by the SV-POW guys, who are apparently coining a new genus for it, so that point will be relatively moot once that paper comes out.

      There have been suggestions that Diplodocus hallorum is synonymous with D. hayi or D. carnegii (or possibly even D. longus), but again, I don’t know enough about diplodocid systematics to speak on that case. I’ve also heard rumblings that Omeisaurus and Mamenchisaurus are overlumped, but then again that’s mostly from G.S. Paul who some authors (see the review by Norman (2012) when it comes to early Cretaceous iguanodontians) consider to be a bit of an extreme splitter when it comes to iguanodonts and mamenchisaur-esque sauropods. Paul has made similar suggestions regarding Tenontosaurus dossi (though the species name should probably be T. dossorum, given that the describer apparently meant to honor the Doss family instead of one individual according to one of the books on Texas Dinosaurs), but nothing has come of it. In the case of Stegosaurus, Bakker has (or perhaps had) been trying to resurrect the name Diracodon for S. stenops, but Carpenter has noted that the holotype of “Diracodon” cannot be assigned to any of the known Stegosaurus species. Finally, in the Spinops paper the species Centrosaurus brinkmani is put in scare quotes, suggesting that the authors may try to erect a new genus for this species.

      Troodon bakkeri? Isn’t that the same thing as “Pectinodon”? I thought that got synonymized with T. formosus or something?

      • Some of these arguments I responded to in my last email, but let me get a bit more specific.

        On some examples:

        Seismosaurus hallorum: with any particular other species of Diplodocus, whose synonymy is based less on gross morphological autapomorphies shared with types and secure referred material than with general shared features and projections of extreme growth — thus raising the ontogenetic specter; moreover, Lovelace et al., who make the more specific referral, do not do so on substantive grounds:

        “Based on the extremely similar morphology of the Seismosaurus axial and pelvic morphology to specimens of Diplodocus, we refer NMMNH 3690 to Diplodocus, and most likely to D. longus.”

        “Likely” is not a secure basis of referral, even if the authors’ suggestion is correct. The phylogenetic analysis performed in the paper also lacks differentiation among the species, a problem when dealing with multi-specific taxa. As I’ve stated elsewhere on this blog, the historic nature of the “genus” forces itself to usurp the “value” taxon of choice when comparing taxa.

        I have my own things to say about Pectinodon bakkeri, referred by various authors around the Troodon complex, but for the most part, I reserve judgement due to the lack of information about variability in the tooth row. Features of troodontid teeth of the “saurornithoidid” type have large denticles, with larger lateral margin teeth, especially on the maxilla; the mesial carinae in often denticulated, and the denticles are “coarse” — that is, relatively large and often not apically angled. The type tooth of bakkeri is differentiable from the type tooth of formosus, and many other Judith-River level teeth in having finer denticulation with a more distinct apical angle, but that’s most it; this comparison implies the teeth are more similar to Sauronithoides mongoliensis and Zanabazar junior, effectively making it an Asian-form taxon in North America. This is one of the primary reasons bakkeri has stuck around.

        As should be clear, it is in many ways a lot easier to talk about species here and there when not dealing with the pretense of an “umbrella” genus, which we then use instead of the species [plural] included. Validating this with taxonomy is quite possibly the best way to resolve the problem, rather than ignore it by retaining the object, subject and baggage of “genus.”

  4. I won’t go into as much detail for the other dinosaurs, but several are thought to belong to a new genus anyway (e.g. mogrebiensis, tamesnensis, minimus), are junior synonyms of other species (e.g. altus, stenops, goodwini, lowei), or already have distinct proposed genera (e.g. kaiseni is Eoceratopsso why factor into a list of “How many new “genus”-like names would we coin”?). Most of the Asian sauropods listed have never been assigned to their genus with good arguments, or distinguished from relatives. Also Bugenasaura is indistinguishable from Thescelosaurus neglectus, while garbanii is distinguishable and based on another specimen (Boyd et al., 2009).

  5. Vahe says:

    Dakosaurus manseli is now recognized as being a distinct genus, Plesiosuchus Owen, 1884 (Young et. al. 2012). These authors also remove the two Argentine species of Purranisaurus (P. casamiquelai and P. westermanni) from that genus because they note that the type species of Purranisaurus (from Chile) is under redescription, which could affect the systematic position of P. casamiquelai and P. westermanni relative to other Metriorhynchus-like genera.

    Young, M. T.; Brusatte, S. L.; De Andrade, M. B.; Desojo, J. B.; Beatty, B. L.; Steel, L.; Fernández, M. S.; Sakamoto, M. et al. (2012). Butler, Richard J. ed. “The Cranial Osteology and Feeding Ecology of the Metriorhynchid Crocodylomorph Genera Dakosaurus and Plesiosuchus from the Late Jurassic of Europe”. PLoS ONE 7 (9): e44985. doi:10.1371/journal.pone.0044985. edit

  6. Vahe says:


    Regarding the following taxa:

    1. Paleorhinus scurriensis is now the type species of the genus Wannia Stocker, 2013.
    2. “Elmisaurus” elegans is included in the new genus Leptorhynchos by Longrich et. al. (2013), who reaffirm the synonymy of Caenagnathus sternbergi with Chirostenotes pergracilis based on the identical proportions of NMC 2367 and NMC 2690 (interestingly, Longrich et. al. do not consider L. elegans to be the same animal as C. sternbergi). Although NMC 2690 and NMC 2367 don’t overlap as they come from different parts of the skeleton, it’s clear from the paper of Longrich et. al. that multiple species of caenagnathoids existed in North America during the middle Campanian (not to mention the as-yet-undescribed Hell Creek caenagnathoid and Epichirostenotes), and that such diversity was not as low as previously thought.
    3. Rodrigues and Kellner (2013) erect the new genus Cimoliopterus for “Pterodactylus” cuvieri, while considering “Pterodactylus” fittoni a nomen dubium possibly synonymous of C. cuvieri. Rodrigues and Kellner also reaffirm the separation of Tropeognathus and Ornithocheirus based on subtle differences in the height of the premaxillary crest and do not consider Anhanguera piscator to be referrable to Coloborhynchus.
    4. Bennett (2013) has coined the genus Ardeadactylus for “Pterodactylus” longicollum.
    5. Psittacosaurus major and P. lujiatuensis have been synonymized with Psittacosaurus houi (Hedrick and Dodson 2013), validating Sereno’s (2010) suggestion that Hongshanosaurus is the same species as P. lujiatuensis.
    6. Parker et. al. (2013) note that Belodon buceros, not Machaeroprosopus validus, is the correct type species of Machaeroprosopus because Maurice Mehl coined Machaeroprosopus as a replacement name for Metarhinus Jaekel 1910 (effectively rendering Arribasuchus a junior objective synonym of Machaeroprosopus). They also refer all nominal species of Pseudopalatus to Machaeroprosopus because previous cladistic analyses find M. buceros and M. pristinus to be sister taxa, with M. jablonskiae and M. mccauleyi basal to buceros and pristinus, sinking Pseudopalatus as a synonym of Machaeroprosopus. In a related development, Hungerbuhler et. al. (2013) describe the new species Machaeroprosopus lottorum, and based on a cladistic analysis, sink Redondasaurus as a junior synonym of Machaeroprosopus. With the synonymy of Redondasaurus with Machaeroprosopus and the naming of M. lottorum, there are now seven named species of Machaeroprosopus (Stocker and Butler 2013 listed M. validus and M. andersoni as Phytosauria incertae sedis, but don’t comment on whether they might be conspecific with M. buceros or M. pristinus).
    7. Young et. al. (2012) remove Aggiosaurus from synonymy with Dakosaurus because the dental character used to synonymize Aggiosaurus with Dakosaurus is homoplastic for Geosaurini.
    8. Dilophosaurus sinensis is sunk as a junior synonym of Sinosaurus triassicus by Xing et. al. (2013).

    Xing, L.; Bell, P. R.; Rothschild, B. M.; Ran, H.; Zhang, J.; Dong, Z.; Zhang, W.; Currie, P. J. (2013). “Tooth loss and alveolar remodeling in Sinosaurus triassicus (Dinosauria: Theropoda) from the Lower Jurassic strata of the Lufeng Basin, China”. Chinese Science Bulletin. doi:10.1007/s11434-013-5765-7. edit

    Hungerbühler, A.; Mueller, B.; Chatterjee, S.; Cunningham, D. P. (2013). “Cranial anatomy of the Late Triassic phytosaur Machaeroprosopus, with the description of a new species from West Texas”. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 103 (3–4): 269. doi:10.1017/S1755691013000364. edit

    Parker, W. G.; Hungerbühler, A.; Martz, J. W. (2013). “The taxonomic status of the phytosaurs (Archosauriformes) Machaeroprosopus and Pseudopalatus from the Late Triassic of the western United States”. Earth and Environmental Science Transactions of the Royal Society of Edinburgh: 1. doi:10.1017/S1755691013000339. edit

    Rodrigues, T.; Kellner, A. (2013). “Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England”. ZooKeys 308: 1. doi:10.3897/zookeys.308.5559. edit

    Stocker, M. R. (2013). “A new taxonomic arrangement for Paleorhinus scurriensis”. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 103 (3–4): 1.
    doi:10.1017/S1755691013000340. edit

    Longrich, N. R.; Barnes, K.; Clark, S.; Millar, L. (2013). “Caenagnathidae from the Upper Campanian Aguja Formation of West Texas, and a Revision of the Caenagnathinae”. Bulletin of the Peabody Museum of Natural History 54: 23. doi:10.3374/014.054.0102. edit

    Bennett, S. C. (2013). “New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus”. Paläontologische Zeitschrift 87 (2): 269–289. doi:10.1007/s12542-012-0159-8. edit

    Hedrick, B. P.; Dodson, P. (2013). “Lujiatun Psittacosaurids: Understanding Individual and Taphonomic Variation Using 3D Geometric Morphometrics”. In Evans, Alistair Robert. PLoS ONE 8 (8): e69265. doi:10.1371/journal.pone.0069265. edit

    • Several of these are apt, and I will alter the list accordingly. Thank you for the work, as I’d not kept aherad of the literature. On some of your points:

      2. “Leptorhynchos” is improperly formed, and not valid. Longrich et al. are working to rectify this situation, as I was told from Nick himself. Thus it must remain.

      5. The correct type species for “Psittacosaurus lujiatunensis” would be “Psittacosaurus houi.” Unfortunately, Sereno, and then in the new paper with his co-authors, determined to default synonyms to “cannot be used as valid species” status when synonymizing, and thus can apparently refer houi to lujiatunensis, when in fact the correct coarse of action is the inverse. This is complicated by the rather nuanced view that taxa based on juvenile types without confirmed corroborating adult types should not form valid species, but are fair game for synonymy. As I agree with the issue that houi being based on a juvenile specimen makes it improper as a type, this also means it shouldn’t be sunk. Otherwise, what you have is sinking lujiatunensis and major into houi, but not into Psittacosaurus, which makes Hongshanosaurus a valid generic container for these taxa.

      As for other points, especially 3. I cannot affirm nor deny “taste” based assessments of taxa. There seems to be a movement amongst taxonomy towards oversplitting as opposed to overlumping. It works for some taxa, not for others. When the taste different is that there are “subtle” variances amongst specimen groups with only two or three individuals to assess, qualifying variation becomes very hard, even when given the auspices of morphometrics and cladistics to “determine” differences are useful taxonomically. When it comes to Psittacosaurus or Ornithocheirus, the conventional wisdom has been to lump them all in, then let God sort them out. But when it comes to pterosaurs especially, specimens for a given species are so few, or individuals so few, as to make evaluating variation practically impossible. There is also the slight issue of what happens when you have one group say a character is “specific” but another says it is “generic;” and foisting a new taxon upon us for that variation, or lumping it, becomes a “taste” issue.

      • Vahe says:


        Regarding Leptorhynchos, Longrich et. al. (2013) publish a corrigendum to their paper erecting the genus Leptorhynchos acknowledging that they accidentally left the genus without a type species. They therefore designate L. gaddisi as the type species of Leptorhynchos, meaning that “Ornithomimus” elegans becom; es a referred species of Leptorhynchos. Given that TMM 45920-1 and ROM 781 represent different parts of the skeleton and the mandible referred to elegans on grounds of size (proportions consistent with those of ROM 781) by Longrich et. al. was used as the basis for referring elegans to Leptorhynchos, some workers may view the referral of “Ornithomimus” elegans to Leptorhynchos with skepticism, but there’s no denying that elegans is not congeneric with Elmisaurus or even Chirostenotes.

        The taxonomic status of Dromiceiomimus samueli remains equivocal; Longrich (2008) referred the holotype of this species to Ornithomimus sp. without giving further comment. However, samueli is probably in need of a new generic name because it is 5 million years older than the type species of Dromiceiomimus and all dinos found in the Horseshoe Canyon Formation are generically distinct from their counterparts in the Dinosaur Park Formation. For now, the generic name for Dromiceiomimus samueli should be in quotes pending a new revision of North American ornithomimosaurs.

        Longrich, 2008. A new, large ornithomimid from the Cretaceous Dinosaur Park Formation of Alberta, Canada: Implications for the study of dissociated dinosaur remains. Palaeontology. 51(4), 983-997.

        Longrich, N. R.; Barnes, K.; Clark, S.; Millar, L. (2013). Correction to “Caenagnathidae from the Upper Campanian Aguja Formation of West Texas, and a Revision of the Caenagnathinae”. Bulletin of the Peabody Museum of Natural History 54 (2): 263-264. doi:

  7. Anonymous says:

    Butler et. al. (2013) just came out with a paper resurrecting Ebrachosuchus from synonymy with Paleorhinus and recognizing Francosuchus angustifrons as a valid species of Paleorhinus. From what I’ve read, Promystriosuchus ehlersi (formerly thought to be congeneric with Paleorhinus) is listed as Phytosauria incertae sedis by Stocker and Butler (2013).

    By the way, Dysalotosaurus is treated as generically distinct from Dryosaurus instead of being referred to Dryosaurus in a number of papers on Dysalotosaurus (Hubner and Rauhut 2010; Hubner 2012).


    Tom R. Hübner and Oliver W. M. Rauhut (2010). “A juvenile skull of Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia), and implications for cranial ontogeny, phylogeny, and taxonomy in ornithopod dinosaurs”. Zoological Journal of the Linnean Society 160 (2): 366–396. doi:10.1111/j.1096-3642.2010.00620.x.

    Butler, R. J., Rauhut, O. W. M., Stocker, M. R., and R. Bronowicz. 2013. Redescription of the phytosaurs Paleorhinus (‘Francosuchus’) angustifrons and Ebrachosuchus neukami from Germany, with implications for Late Triassic biochronology. Zoological Journal of the Linnean Society Early View. DOI: 10.1111/zoj.12094

    Stocker, M. R.; Butler, R. J. (2013). “Phytosauria”. Geological Society, London, Special Publications. doi:10.1144/SP379.5. edit

    Hübner, T. R. (2012). “Bone Histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia) – Variation, Growth, and Implications”. In Laudet, Vincent. PLoS ONE 7 (1): e29958. doi:10.1371/journal.pone.0029958. PMC 3253128. PMID 22238683. edit

  8. Anonymous says:


    The following new changes should be made:

    1. Diplodocus hayi has been renamed Galeamopus. Also Brontosaurus is revalidated and Elosaurus and Eobrontosaurus synonymized with Brontosaurus rather than Apatosaurus (Tschopp et al. 2015).

    2. Campbell et al. (2016) list Chasmosaurus kaiseni as indeterminate within Chasmosaurus (along with Eoceratops), but they synonymize Mojoceratops with Chasmosaurus russelli.

    3. A new description of Purranisaurus by Herrera et al. (2015) fails to support referral of Metriorhynchus casamiquelai and M. westermanni to Purranisaurus. Therefore, M. casamiquelai and M. westermanni should be removed from the list for now, since there is a chance a new genus may be erected for those two species.

    4. Stegosaurus longispinus has been renamed Alcovasaurus (Galton and Carpenter 2016).

    5. Probactrosaurus mazongshanensis has been renamed Gongpoquansaurus (You et al. 2014).

    6. Omeisaurus jungshiensis is mistakenly included on this list, which is supposed to only include non-type species.

    7. Prosaurolophus blackfeetensis has been synonymized with P. maximus by McGarritty et al. (2013).

    Campbell, J.A., Ryan, M.J., Holmes, R.B., and Schröder-Adams, C.J. (2016). A Re-Evaluation of the chasmosaurine ceratopsid genus Chasmosaurus (Dinosauria: Ornithischia) from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Western Canada. PLoS ONE, 11(1): e0145805. doi:10.1371/journal.pone.0145805

    Galton, Peter M. & Carpenter, Kenneth, 2016, “The plated dinosaur Stegosaurus longispinus Gilmore, 1914 (Dinosauria: Ornithischia; Upper Jurassic, western USA), type species of Alcovasaurus n. gen.”, Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen 279(2): 185-208

    Y. Herrera, Z. Gasparini, and M. S. Fernández. 2015. Purranisaurus potens Rusconi, an enigmatic metriorhynchid from the Late Jurassic–Early Cretaceous of the Neuquén Basin. Journal of Vertebrate Paleontology 35(2):e904790

    McGarrity, C. T.; Campione, N. E.; Evans, D. C. (2013). “Cranial anatomy and variation in Prosaurolophus maximus (Dinosauria: Hadrosauridae)”. Zoological Journal of the Linnean Society 167 (4): 531–568. doi:10.1111/zoj.12009.

    Tschopp, E.; Mateus, O. V.; Benson, R. B. J. (2015). “A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)”. PeerJ 3: e857. doi:10.7717/peerj.857.

    You, H.-I.; Li, D.-Q.; Dodson, P. (2014). “Gongpoquansaurus mazongshanensis (Lü, 1997) comb. nov. (Ornithischia: Hadrosauroidea) from the Early Cretaceous of Gansu Province, Northwestern China”. In Eberth, David A.; Evans, David C. Hadrosaurs. Indiana University Press. pp. 73–76. ISBN 978-0-253-01390-3.

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