29Bulletin of Zoological Nomenclature 77 (30 April 2020) ISSN 2057-0570 (online)
Case 3815 – Tyrannosauridae Osborn, 1906 (Dinosauria,
Theropoda): proposed conservation by reversal of precedence with
deinodonTidae Cope, 1866 and drypTosauridae Marsh, 1890
Vertebrate Paleontological Institute of Incheon, Incheon 21974, Republic of
Korea / Biological Sciences, Inha University, Incheon 22212, Republic of Korea
Abstract. The purpose of this application, under Article 23.9.3 of the Code, is to
conserve at both the family and superfamily level the widely used family-group name
Tyrannosauridae (-oidea) Osborn, 1906 (Dinosauria, Theropoda), which is threatened by
its senior subjective synonyms deinodonTidae (-oidea) Cope, 1866 and drypTosauridae
(-oidea) Marsh, 1890. Strict application of the Code would result in unnecessary confusion
in dinosaur taxonomy since the names Tyrannosauridae and Tyrannosauroidea have
been used consistently in the vertebrate paleontological literature since the 1970s with
only a very few exceptions.
Keywords. Nomenclature; taxonomy; Dinosauria; Theropoda; Tyrannosauroidea;
Tyrannosauridae; deinodonToidea; deinodonTidae; drypTosauroidea; drypTosauridae.
1. In 1855, Ferdinand Vandeveer Hayden collected several large theropod teeth
from the Upper Cretaceous Judith River Formation in Montana, and Leidy (1856: 72)
erected Deinodon horridus Leidy, 1856 based on them. Cope (1866: 279) coined the
family-level name dinodonTidae Cope, 1866 for this genus (which he incorrectly spelled
as Dinodon) and species, and Brown (1914: 377) justiably emended it (see Articles
32.5.3 and 35.4.1 of the Code) to deinodonTidae Cope, 1866. Originally, Cope (1866)
included Deinodon and Laelaps Cope, 1866 (the latter preoccupied by Laelaps Koch,
1836, currently Dryptosaurus Marsh, 1877, type species Dryptosaurus aquilunguis
(Cope, 1877)) in this family, and Matthew & Brown (1922) considered Deinodon,
Dryptosaurus, Gorgosaurus Lambe, 1914, Albertosaurus Osborn, 1905, Tyrannosaurus
Osborn, 1905 and Dynamosaurus Osborn, 1905 as deinodontids. Until the 1970s, the name
deinodonTidae was applied to the theropod dinosaurs now known as Tyrannosauridae
Osborn, 1906. The concepts are nearly identical and both names have been considered to
be subjective synonyms of each other (e.g., Russell, 1970; Holtz, 2004).
2. Today, Deinodon horridus is regarded as a nomen dubium that possibly represents
teeth shed from contemporaneous Gorgosaurus libratus Lambe, 1914 (e.g., Russell, 1970).
However, separating the isolated teeth of G. libratus from those of the contemporaneous
Bulletin of Zoological Nomenclature 77 (30 April 2020) ISSN 2057-0570 (online)30
tyrannosaurine Daspletosaurus torosus Russell, 1970 is nearly impossible because
they are very similar in morphology (Buckley et al., 2010) and because the denticle
density ranges of teeth of the two genera overlap (Carr & Williamson, 2000). Generally,
tyrannosaurid (= deinodontid) teeth, including the type specimens of Deinodon horridus,
are morphologically uniform in having labiolingually expanded basal parts and carinae
that are offset from the mesial and distal edges (e.g., Holtz, 2004). Although Deinodon
horridus may be referable to this family, e.g. as Tyrannosauridae incertae sedis, its
teeth have no distinctive features that allow it to be referred to either of the currently
recognized subfamilies, Tyrannosaurinae Osborn, 1906 or alberTosaurinae Currie,
Hurum & Sabath, 2003. If it were referred to either, DeinodonTinae Cope, 1866 would
become the valid name of the subfamily involved.
3. Marsh (1890: 424) erected the family-group taxon drypTosauridae Marsh, 1890
to encompass Dryptosaurus along with other North American theropods. However, the
highly fragmentary nature of the holotype of Dryptosaurus aquilunguis has made its
classication highly controversial (e.g., Carpenter et al., 1997; Brusatte et al., 2011).
The name drypTosauridae was last used by Carpenter et al. (1997) as those authors
were uncertain about the evolutionary relationships of Dryptosaurus with other theropods
and treated the family as monotypic. Otherwise, a close afnity of Dryptosaurus with
deinodontids (= tyrannosaurids) has been accepted since the late 1800s (e.g., Cope, 1866;
Brown, 1914; Matthew & Brown, 1922). Most recent phylogenetic studies, as well as a
redescription of the holotype of the type species Dryptosaurus aquilunguis, have placed
Dryptosaurus as a basal coelurosaurian theropod nested deep within Tyrannosauroidea
Osborn, 1906 (e.g., Holtz, 2004; Carr et al., 2005; Carr & Williamson, 2010; Brusatte
et al., 2010; Loewen et al., 2013; Brusatte & Carr, 2016; Carr et al., 2017), and none of
these works has used the family name drypTosauridae as taxonomically valid.
4. Osborn (1906: 283) coined the family name Tyrannosauridae Osborn, 1906 for
Tyrannosaurus Osborn, 1905, and this name is now used to encompass large, basal,
hypercarnivorous coelurosaurs such as Gorgosaurus libratus, Albertosaurus sarcophagus
Osborn, 1905 and Tyrannosaurus rex Osborn, 1905. Walker (1964) proposed to use a
superfamily Tyrannosauroidea to group Tyrannosauridae with several pseudosuchians
and spinosauridae Stromer, 1915, but this treatment was not supported by subsequent
authors. Although Tyrannosauroidea and its subgroup Tyrannosauridae were considered
as carnosaurs for many decades (e.g., Osborn, 1906; Walker, 1964; Russell, 1970), they
are now treated as either the basal-most coelurosaurs or as being grouped among other
basal coelurosaurs at a level more derived than CompsognaThidae Cope, 1871 (e.g., Holtz,
2004; Loewen et al., 2013; Brusatte & Carr, 2016; Yun, 2016). While many works before
the 1970s used deinodonTidae instead of Tyrannosauridae (e.g., Brown, 1914; Matthew
& Brown, 1922; Gilmore, 1946; Maleev, 1955), most modern authors (e.g., Olshevsky,
1991; Carpenter, 1992; Holtz, 1994, 1996, 2000, 2001, 2004, 2012; Carpenter et al.,
1997; Padian et al., 1999; Sereno, 1999; Carr & Williamson, 2000, 2010; Currie, 2003;
Currie et al., 2003; Carr et al., 2005, 2017; Sereno et al., 2005, 2009; Sereno & Brusatte,
2009; Brusatte et al., 2010, 2011, 2012, 2014, 2016; Buckley et al., 2010; Brusatte &
Benson, 2013; Loewen et al., 2013; Hendrickx et al., 2015; Brusatte & Carr, 2016; Yun,
2016, 2017; Cau, 2018; Nesbitt et al., 2019) have followed Russell (1970) in preferring
Tyrannosauridae on the grounds that Deinodon horridus is a nomen dubium with type
specimens that are not referable to any genus- or species-group taxon.
5. Nothing in the current Code (ICZN, 1999) implies the invalidation of a family-
31Bulletin of Zoological Nomenclature 77 (30 April 2020) ISSN 2057-0570 (online)
group name when the taxonomic validity of its type genus is dubious. Olshevsky (1991)
rst recognized this, but he preferred to use Tyrannosauridae because deinodonTidae had
rst appeared as an emendation of dinodonTidae in Brown (1914) and thus seemed to him
to be junior to Tyrannosauridae proposed in 1906. He was incorrect, as Article 32.2.2 of
the Code requires a justied emendation to take the authorship and date of the original
publication, i.e. Cope, 1866. Additionally, according to Article 36, “a name established
for a taxon at any rank in the family group is deemed to have been simultaneously
established for nominal taxa at all other ranks in the family group”. Therefore, just as
deinodonTidae has priority over Tyrannosauridae, so do deinodonToidea Cope, 1866
and drypTosauroidea Marsh, 1890 have priority over Tyrannosauroidea Osborn, 1906.
6. Both deinodonTidae and drypTosauridae were proposed before 1899, but they
were commonly used in pre-1970s literature and even more recently (e.g., Carpenter et
al., 1997; Martyniuk, 2012). The present case cannot be resolved by invoking prevailing
usage under Art. 23.9.1 because the requirements of Art. 22.214.171.124 are not met. Insisting
on a reversion of Tyrannosauridae to deinodonTidae (or drypTosauridae) would create
unnecessary confusion in taxonomy since Tyrannosauridae has been used in the vast
majority of theropod phylogenetic and taxonomic studies during the past half-century.
The same applies to Tyrannosauroidea. In the interest of nomenclatural stability, it
seems necessary to invoke Article 23.9.3 of the Code and ask the Commission to use its
plenary power to conserve the widely used family name Tyrannosauridae Osborn, 1906
by reversal of precedence with deinodonTidae Cope, 1866 and drypTosauridae Marsh,
7. The International Commission on Zoological Nomenclature is accordingly asked:
(1) to use its plenary power to rule:
(a) that the family-group name Tyrannosauridae Osborn, 1906 is to be
given precedence over deinodonTidae Cope, 1866 whenever the two are
considered to be synonyms;
(b) that the family-group name Tyrannosauridae Osborn, 1906 is to be
given precedence over drypTosauridae Marsh, 1890 whenever the two
are considered to be synonyms;
(2) to place on the Ofcial List of Family-Group Names in Zoology the following
(a) Tyrannosauridae Osborn, 1906, type genus: Tyrannosaurus Osborn,
1905 (Theropoda) with the endorsement that it is to be given precedence
over deinodonTidae Cope, 1866 and drypTosauridae Marsh, 1890,
whenever the rst is considered to be a synonym of either of the last
two, as ruled in (1) above;
(b) deinodonTidae Cope, 1866, type genus: Deinodon Leidy, 1856
(Theropoda) with the endorsement that it is not to be given priority over
Tyrannosauridae Osborn, 1906 whenever the two are considered to be
synonyms, as ruled in (1)(a) above; and
(c) drypTosauridae Marsh, 1890, type genus: Dryptosaurus Marsh 1877
(Theropoda) with the endorsement that it is not to be given priority over
Tyrannosauridae Osborn, 1906 whenever the two are considered to be
synonyms, as ruled in (1)(b) above.
Bulletin of Zoological Nomenclature 77 (30 April 2020) ISSN 2057-0570 (online)32
The author thanks the ICZN secretary Gwynne Lim, the Editor Neal L. Evenhuis, and
two anonymous reviewers for their comments and valuable discussions. Special thanks
go to Yeon-Woo Lee, Bong-Hwan Ji, Dong-Yoon Lee, Dong-Geun Lee, Ha-Jun Lee,
Hyo-Jin Ji, Yeon-Sung Kim and Ga-Hee Kim for their support and care.
Brown B (1914) Cretaceous Eocene correlations in New Mexico, Wyoming, Montana. Bulletin of
the Geological Society of America 25: 355–380.
Brusatte SL, Benson RBJ (2013) The systematics of Late Jurassic tyrannosauroids (Dinosauria:
Theropoda) from Europe and North America. Acta Palaeontologica Polonica 58: 47–54.
Brusatte SL, Averianov A, Sues H-D, Muir A, Butler IB (2016) New tyrannosaur from the mid-
Cretaceous of Uzbekistan claries evolution of giant body sizes and advanced senses in tyrant
dinosaurs. Proceedings of the National Academy of Sciences 113: 3447–3452.
Brusatte SL, Benson RBJ, Norell MA (2011) The anatomy of Dryptosaurus aquilunguis (Dinosauria:
Theropoda) and a review of its tyrannosauroid afnities. American Museum Novitates 3717:
Brusatte SL, Carr TD (2016) The phylogeny and evolutionary history of tyrannosauroid dinosaurs.
Scientic Reports 6: 20252. [8 pp.]
Brusatte, SL, Carr TD, Norell MA (2012) The osteology of Alioramus, a gracile and long-snouted
tyrannosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Mongolia. Bulletin of the
American Museum of Natural History 366: 1–197.
Brusatte SL, Norell MA, Carr TD, Erickson GM, Hutchinson JR, Balanoff AM, Bever GS,
Choiniere JN, Makovicky PJ, Xu X (2010) Tyrannosaur paleobiology: new research on ancient
exemplar organisms. Science 329: 1481–1485.
Brusatte SL, Lloyd GT, Wang SC, Norell MA (2014) Gradual assembly of avian body plan
culminated in rapid rates of evolution across the dinosaur-bird transition. Current Biology 24:
Buckley LG, Larson DW, Reichel M, Samman T (2010) Quantifying tooth variation within a single
population of Albertosaurus sarcophagus (Theropoda: Tyrannosauridae) and implications for
identifying isolated teeth of tyrannosaurids. Canadian Journal of Earth Sciences 47: 1227–1251.
Carpenter K (1992) Tyrannosaurids (Dinosauria) of Asia and North America [pp. 250–268]. In:
Mateer NJ, Chen PJ (Eds), Aspects of nonmarine Cretaceous geology. China Ocean Press,
Carpenter K, Russell DA, Baird D, Denton R (1997) Redescription of the holotype of Dryptosaurus
aquilunguis (Dinosauria: Theropoda) from the Upper Cretaceous of New Jersey. Journal of
Vertebrate Paleontology 17: 561–573.
Carr TD, Varricchio DJ, Sedlmayr JC, Roberts EM, Moore JR (2017) A new tyrannosaur with
evidence for anagenesis and crocodile-like facial sensory system. Scientic Reports 7: 44942.
Carr TD, Williamson TE (2000) A review of Tyrannosauridae (Dinosauria, Coelurosauria) from
New Mexico. New Mexico Museum of Natural History and Science Bulletin 17: 113–145.
Carr TD, Williamson TE (2010) Bistahieversor sealeyi, gen. et sp. nov. a new tyrannosauroid
from New Mexico and the origin of deep snouts in Tyrannosauroidea. Journal of Vertebrate
Paleontology 30: 1–16.
Carr TD, Williamson TE, Schwimmer DR (2005) A new genus and species of tyrannosauroid
from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama. Journal of
Vertebrate Paleontology 25: 119–143.
Cau A (2018) The assembly of the avian body plan: a 160 million year long process. Bollettino
della Società Paleontologica Italiana 57: 1–25.
Cope ED (1866) On the remains of a gigantic extinct dinosaur, from the Cretaceous Green Sand
33Bulletin of Zoological Nomenclature 77 (30 April 2020) ISSN 2057-0570 (online)
of New Jersey. Proceedings of the Academy of Natural Sciences of Philadelphia 18: 275–279.
Cope ED (1871) On the homologies of some of the cranial bones of the Reptilia, and on the
systematic arrangement of the class. Proceedings of the American Association for the
Advancement of Science 19: 194–247.
Currie PJ (2003) Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta,
Canada. Acta Palaeontologica Polonica 48: 191–226.
Currie PJ, Hurum JH, Sabath K (2003) Skull structure and evolution in tyrannosaurid dinosaurs.
Acta Palaeontologica Polonica 48: 227–234.
Gilmore CW (1946) A new carnivorous dinosaur from the Lance Formation of Montana.
Smithsonian Miscellaneous Collections 106: 1–19.
Hendrickx C, Hartman SA, Mateus O (2015) An overview on non-avian theropod discoveries and
classication. PalArch’s Journal of Vertebrate Palaeontology. 12: 1–73.
Holtz TR (1994) The phylogenetic position of the Tyrannosauridae: Implications for theropod
systematics. Journal of Paleontology 68: 1100–1117.
Holtz TR (1996) Phylogenetic taxonomy of the Coelurosauria (Dinosauria: Theropoda). Journal of
Paleontology 70: 536–538.
Holtz TR (2000) A new phylogeny of the carnivorous dinosaurs. Gaia 15: 5–61.
Holtz TR (2001) The phylogeny and taxonomy of the Tyrannosauridae [pp. 64–83]. In: Tanke DH,
Carpenter K (Eds). Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of
Philip J. Currie. Indiana University Press, Bloomington.
Holtz TR (2004) Tyrannosauroidea [pp. 111–136]. In: Weishampel DB, Dodson P, Osmólska H
(Eds), The Dinosauria. Second Edition. University of California Press, Berkeley.
Holtz TR (2012) Theropods [pp. 346–378]. In: Brett-Surman MK, Holtz TR, Farlow JO (Eds), The
Complete Dinosaur Second Edition. Indiana University Press, Bloomington.
ICZN (International Commission on Zoological Nomenclature) (1999) International Code of
Zoological Nomenclature. Fourth edition. International Trust for Zoological Nomenclature,
London, xxix + 306 pp.
Koch CL (1836) Deutschlands Crustaceen, Myriapoden und Arachniden. Ein Beitrag zur Deutschen
Fauna 5: 1–24.
Lambe LM (1914) On a new genus and species of carnivorous dinosaur from the Belly River
Formation of Alberta, with a description of the skull of Stephanosaurus marginatus from the
same horizon. Ottawa Naturalist 28: 13–20.
Leidy J (1856) Notices of the remains of extinct reptiles and shes, discovered by Dr. F.V. Hayden
in the badlands of the Judith River, Nebraska Territory. Proceedings of the Academy of Natural
Sciences of Philadelphia 8: 72–73.
Loewen MA, Irmis RB, Sertich JJW, Currie PJ, Sampson SD (2013) Tyrant dinosaur evolution
tracks the rise and fall of Late Cretaceous oceans. PLoS ONE 8 (11): e79420. [14 pp.]
Maleev EA (1955) [Giant carnivorous dinosaurs of Mongolia]. Doklady Akademii Nauk SSSR 104:
634–637. [In Russian.]
Marsh OC (1890) Additional characters of the Ceratopsidae, with notice of new Cretaceous
dinosaurs. American Journal of Science 39: 418–426.
Martyniuk M (2012) A eld guide to Mesozoic birds and other winged dinosaurs. Pan Aves,
Vernon, New Jersey, 189 pp.
Matthew WD, Brown B (1922) The family Deinodontidae, with notice of a new genus from the
Cretaceous of Alberta. Bulletin of the American Museum of Natural History 46: 367–385.
Nesbitt SJ, Denton RK, Loewen MA, Brusatte SL, Smith ND, Turner AH, Kirkland JI, McDonald
AT, Wolfe DG (2019) A mid-Cretaceous tyrannosauroid and the origin of North American end-
Cretaceous dinosaur assemblages. Nature Ecology and Evolution 3: 892–899.
Olshevsky G (1991) A revision of the parainfraclass Archosauria Cope, 1869, excluding the
advanced Crocodylia. Mesozoic Meanderings 2: 1–196.
Osborn HF (1905) Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the
American Museum of Natural History 21: 259–265.
Bulletin of Zoological Nomenclature 77 (30 April 2020) ISSN 2057-0570 (online)34
Osborn HF (1906) Tyrannosaurus, Upper Cretaceous carnivorous dinosaur (second communication).
Bulletin of the American Museum of Natural History 22: 281–296.
Padian K, Hutchinson TR, Holtz TR (1999) Phylogenetic denitions and nomenclature of the
major taxonomic categories of the carnivorous Dinosauria (Theropoda). Journal of Vertebrate
Paleontology 19: 69–80.
Russell DA (1970) Tyrannosaurs from the Late Cretaceous of western Canada. National Museum
of Natural Science Publications in Palaeontology 1: 1–34.
Sereno PC (1999) A rationale for dinosaurian taxonomy. Journal of Vertebrate Paleontology 19:
Sereno PC, McAllister S, Brusatte SL (2005) TaxonSearch: A relational database for suprageneric
taxa and phylogenetic denitions. PhyloInformatics 8: 1–25.
Sereno PC, Brusatte SL (2009) Comparative assessment of tyrannosaurid interrelationships. Journal
of Systematic Palaeontology 7: 455–470.
Sereno PC, Tan L, Brusatte SL, Kriegstein HJ, Zhao X, Cloward K (2009) Tyrannosaurid skeletal
design rst evolved at small body size. Science 326: 418–422.
Stromer E (1915) Ergebnisse der Forschungsreisen Prof. Stromers in den Wüsten Ägyptens. II
Wirbeltier-Reste der Baharîje-Stufe (unterstes Cenoman). 3. Das Original des Theropoden
Spinosaurus aegyptiacus nov. gen., nov. spec. Abhandlungen der Königlich Bayerischen
Akademie der Wissenschaften, Mathematisch–physikalische Klasse 28: 1–32.
Walker AD (1964) Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs.
Philosophical Transactions of the Royal Society of London (Series B) 248: 53–134.
Yun C (2016) A review of the basal tyrannosauroids (Saurischia: Theropoda) of the Jurassic Period.
Volumina Jurassica 14: 159–164.
Yun C (2017) Testing the hypotheses of the origin of Tyrannosaurus rex: immigrant species, or
native species? The Journal of Paleontological Sciences 7: 1–9.
Acknowledgement of receipt of this application was published in BZN 76: 166.
Comments on this case are invited for publication (subject to editing) in the Bulletin; they should
be sent to the Secretariat, International Commission on Zoological Nomenclature, c/o Lee Kong
Chian Natural History Museum, 2 Conservatory Drive, Singapore 117377, Republic of Singapore