Dentary groove morphology does not distinguish ‘Nanotyrannus’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988”

  title={Dentary groove morphology does not distinguish ‘Nanotyrannus’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988”},
  author={Stephen Louis Brusatte and Thomas D. Carr and Thomas E. Williamson and Thomas Richard Holtz and David W. E. Hone and Scott A. Williams},
  journal={Cretaceous Research},
Growing up Tyrannosaurus rex: Osteohistology refutes the pygmy “Nanotyrannus” and supports ontogenetic niche partitioning in juvenile Tyrannosaurus
Together, the results support the synonomization of “Nanotyrannus” into Tyrannosaurus and fail to support the hypothesized presence of a sympatric tyrannosaurid species of markedly smaller adult body size, but suggest that this species singularly exploited mid- to large-sized theropod niches at the end of the Cretaceous.
Corrections and comments on the taxonomic value of anatomical features of tyrannosaurid theropods
  • Chan-Gyu Yun
  • Environmental Science, Biology
    Anatomical record
  • 2020
Whether some of the characters that were used for the identification of the articulated tyrannosaurid skeleton with controversial identity are taxonomically meaningful or not is discussed.
A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system
A new species of Tyrannosaurid from the upper Two Medicine Formation of Montana supports the presence of a Laramidian anagenetic (ancestor-descendant) lineage of Late Cretaceous tyrannosaurids, suggesting that anagenesis could have been a widespread mechanism generating species diversity amongst dinosaurs, and perhaps beyond.
The Cranial Osteology of Buitreraptor gonzalezorum Makovicky, Apesteguía, and Agnolín, 2005 (Theropoda, Dromaeosauridae), from the Late Cretaceous of Patagonia, Argentina
A phylogenetic analysis was performed, recovering Buitreraptor as an unenlagiine dromaeosaurid, in agreement with previous works, including characters not previously considered for this taxon, such as the presence of the mylohyoid foramen.
Baby tyrannosaurid bones and teeth from the Late Cretaceous of western North America
Tyrannosaurids were the apex predators of Late Cretaceous Laurasia and their status as dominant carnivores has garnered considerable interest since their discovery, both in the popular and scientific
The role of ontogeny on character polarization in early dinosaurs: a new specimen from the Late Triassic of southern Brazil and its implications
Light is shed on the morphologic pathways seen during dinosauromorph ontogenetic development, which is crucial to more reliably assess phylogenetic reconstructions and macroevolutionary patterns of this widespread and successful group.
Assessing ontogenetic maturity in extinct saurian reptiles
The various methods that have been used to assess maturity in every major saurian group are described, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method‐specific pitfalls, best practices, and fruitful directions for future research.
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.
Size-driven preservational and macroecological biases in the latest Maastrichtian terrestrial vertebrate assemblages of North America
Abstract. The end-Cretaceous (K/Pg) mass extinction event is the most recent and well-understood of the “big five” and triggered establishment of modern terrestrial ecosystem structure. Despite the
The influence of juvenile dinosaurs on community structure and diversity
It is demonstrated that juvenile megatheropods likely filled the mesocarnivore niche, resulting in reduced overall taxonomic diversity, and suggests that ontogenetic niche shift was an important factor in generating dinosaur community structure and diversity.


Nanotyrannus, a new genus of pygmy tyrannosaur, from the Latest Cretaceous of Montana
Nanotyrannus, type species Gorgosaurus lancensis, is the smallest known tyrannosaurid dinosaur and represents, with Tyrannosaurus rex, the last and most advanced members of the Family Tyran­
Bistahieversor sealeyi, gen. et sp. nov., a New Tyrannosauroid from New Mexico and the Origin of Deep Snouts in Tyrannosauroidea
Skeletal remains of Late Cretaceous (Campanian and Maastrichtian) tyrannosauroids are rare in southwestern North America (Carr and Williamson, 2000). Historically, the identity and diversity of
Cranial Osteology of a Juvenile Specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia
This juvenile specimen suggests that T. bataar would have changed its dietary niches during ontogeny, and the numbers of alveoli in the maxilla and dentary are the same as those in adults, suggesting that they do not change onto genetically in T. Bataar and thus are not consistent with the hypothesis that the number ofAlveoli decreases ontogenetically in tyrannosaurids.
Cladistic analysis indicates the new taxon is a basal tyrannosauroid and its presence in eastern North America suggests that the recent common ancestor of Tyrannosauridae probably evolved following the transgression of the Western Interior Seaway.
Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America
The tooth taxon Aublysodon mirandus was reinstated following the collection of nondenticulate tyrannosaurid premaxillary teeth from late Maastrichtian deposits in western North America, but is a nomen dubium because of the small size of Aublysdon crowns and evidence that some denticles develop late in growth in theropods.
The Osteology of Alioramus, A Gracile and Long-Snouted Tyrannosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Mongolia
Anatomical comparisons indicate that the long skull of Alioramus is an autapomorphic feature that is proportionally longer than in any other known tyrannosaurid specimen, including juveniles, and that AlIORamus is morphologically distinctive relative to similarly sized individuals of the contemporary and sympatric Tarbosaurus.
Reanalysis of “Raptorex kriegsteini”: A Juvenile Tyrannosaurid Dinosaur from Mongolia
It is suggested that there is currently no evidence to support the conclusion that tyrannosaurid skeletal design first evolved in the Early Cretaceous at small body size, and the probable juvenile status of LH PV18 makes its use as a holotype unreliable.
Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria)
An increase in tooth width, accompanied by loss of tooth positions, and a global shift from an immature gracile to a mature robust morphotype in the craniofacial skeleton typifies the ontogenetic changes in T. rex.
Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada
  • P. Currie
  • Environmental Science, Geography
  • 2003
It is concluded that the most parsimonious interpretation of relationships leads to the separation of the two species of Albertosaurus into Gorgosaurus libratus from the Campanian Dinosaur Park Formation and Albertosaurus sarcophagus from the upper Campanian/lower Maastrichtian Horseshoe Canyon Formation.