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Case 3815 – Tyrannosauridae Osborn, 1906 (Dinosauria, Theropoda): proposed conservation by reversal of precedence with Deinodontidae Cope, 1866 and Dryptosauridae Marsh, 1890

Authors:

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.
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
Chan-gyu Yun
Vertebrate Paleontological Institute of Incheon, Incheon 21974, Republic of
Korea / Biological Sciences, Inha University, Incheon 22212, Republic of Korea
(changyu1015@naver.com)
http://zoobank.org/urn:lsid:zoobank.org:pub:CF7C9063-757B-447E-B892-4F951D8C4E2F
http://dx.doi.org/10.21805/bzn.v77.a008
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) justiably 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
classication 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 afnity 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 justied 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. 23.9.1.1 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,
1890.
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 Ofcial List of Family-Group Names in Zoology the following
names:
(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
Acknowledgements
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.
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It is an undoubtable fact that Tyrannosaurus rex is the most iconic dinosaur species of all time. However, it is currently debatable whether this species has a North American origin or Asian origin. In this paper, I test these two hypotheses based on current fossil records and former phylogenetic analyses. Phylogenetic and fossil evidence, such as derived tyrannosaurine fossils of Asia, suggests that the hypothesis of an Asian origin of Tyrannosaurus rex is the most plausible one, but this is yet to be certain due to the scarcity of fossil records.
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The theropod family Tyrannosauridae (Dinosauria) is composed of four genera and seven species. All taxa are known from nearly complete skeletons and/ or skulls, thus making it one of the best documented large theropod families. The stratigraphic and palaeobiogeographic distribution of the Tyrannosauridae extends from the lower Campanian to upper Maastrichtian of North America, and to the Campanian-Maastrichtian of Asia.
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Tyrannosauroids—the group of carnivores including Tyrannosaurs rex—are some of the most familiar dinosaurs of all. A surge of recent discoveries has helped clarify some aspects of their evolution, but competing phylogenetic hypotheses raise questions about their relationships, biogeography, and fossil record quality. We present a new phylogenetic dataset, which merges published datasets and incorporates recently discovered taxa. We analyze it with parsimony and, for the first time for a tyrannosauroid dataset, Bayesian techniques. The parsimony and Bayesian results are highly congruent, and provide a framework for interpreting the biogeography and evolutionary history of tyrannosauroids. Our phylogenies illustrate that the body plan of the colossal species evolved piecemeal, imply no clear division between northern and southern species in western North America as had been argued, and suggest that T. rex may have been an Asian migrant to North America. Over-reliance on cranial shape characters may explain why published parsimony studies have diverged and filling three major gaps in the fossil record holds the most promise for future work.