Tyrannosaurinae

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Tyrannosaurinae
Temporal range:
Ma
Skull of Alioramus.
Skull of Tyrannosaurus.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Tyrannosauridae
Subfamily: †Tyrannosaurinae
Osborn, 1906
Type genus
†Tyrannosaurus
Osborn, 1905
Subgroups[2]

Tyrannosaurinae (sometimes referred to as tyrannosaurines) is one of the two extinct subfamilies of

Tyrannosaurus rex
. There were at least 30 different species of tyrannosaurines.

History of discovery

Deinodon teeth, the earliest known tyrannosaurid remains

The first remains of tyrannosaurids were uncovered during expeditions led by the

Manospondylus gigas. This discovery was mostly overlooked for over a century, and caused controversy in the early 2000s when it was discovered that this material actually belonged to, and had name priority over, Tyrannosaurus rex.[3] Later in 1905 Henry Fairfield Osborn described two tyrannosaur specimens that had been collected in Montana and Wyoming during a 1902 expedition of the American Museum of Natural History, led by Barnum Brown. Initially, Osborn considered these to be distinct species. The first, he named Dynamosaurus imperiosus ("emperor power lizard"), and the second, Tyrannosaurus rex ("king tyrant lizard"). A year later, Osborn recognized that these two specimens actually came from the same species. Despite the fact that Dynamosaurus had been found first, the name Tyrannosaurus had appeared one page earlier in his original article describing both specimens. Therefore, according to the International Code of Zoological Nomenclature (ICZN), the name Tyrannosaurus was used.[4]

The second described representative of the tyrannosaurines,

Soviet-Mongolian expedition to the Gobi Desert in the Mongolian Ömnögovi Province in 1946. The holotype was named as Tyrannosaurus bataar by Evgeny Maleev as Tyrannosaurus bataar.[5] The genus Tarbosaurus was also described in the same year based on PIN 551–2, a specimen with a skull and skeletal remains discovered by the same expedition in 1948 and 1949 as Tarbosaurus efremovi.[6] It was only in 1965 that Ty. bataar and Ta. efremovi were the same species, the latter being a younger animal, and distinct from Tyrannosaurus recognized by A.K. Rozhdestvensky who recombined the species as Tarbosaurus bataar.[7]

In the 1970s saw the description of two genera. In 1970 saw the publication of

metatarsals found by a joint Soviet-Mongolian expedition to the Gobi Desert in the early 1970s found these remains at a locality known as Nogon-Tsav in the Mongolian province of Bayankhongor, Nemegt Formation.[9]

From 1977 to 2009 saw the publications of several genera. In Asia they include Shanshanosaurus (1977),[10] Maleevosaurus (1992),[11] and Raptorex (2009),[12] while in North America saw Nanotyrannus (1988),[13] Dinotyrannus and Stygivenator (1995).[14] These genera, however are controversial as the remains of these animals are immature or juvenile individuals. As of 2021 it is widely understood that the Asian specimens are early growth stages of Tarbosaurus,[15][16][17] while the North American specimens are those of Tyrannosaurus.[18][19]

Skeletal reconstruction of two tyrannosaurs superimposed over each other, with known bones highlighted in yellow; photographs of various fossils appear below
Skeletal diagrams showing holotype remains of Lythronax (A) and a Teratophoneus specimen (B). N–P show selected bones of the former

Valid genera would not be named until the 2010s, where in 2011 announced the publication of

metatarsals III and IV.[24] Lythronax, the oldest known member of Tyrannosauridae, was described in 2013 by Mark A. Loewen and colleagues from a nearly complete specimen that was uncovered in 2009 in the Wahweap Formation of the Grand Staircase–Escalante National Monument.[25]

Natural history

Description

Size of A. remotus compared with a human
The specimens "Sue", AMNH 5027, "Stan", and "Jane", to scale with a human.

In comparison to the albertosaurines, tyrannosaurines were more heavily built and larger. The alioramin genera of Qianzhousaurus and Alioramus, however, were the exception, as they were more comparable in built to albertosaurines and have longirostrine snouts.[24] Like albertosaurines, tyrannosaurines also had heterodont dentition, large heads design to catch and kill their prey, and short didactyl arms. Based on the growth stages of Tyrannosaurus (and possibly Tarbosaurus[17]), tyrannosaurines undergone ontogenetic changes from gracile or slender, semi-longirostrine immatures to robust, heavy-headed adults. This implies that these animals occupy different ecological niches as they developed.[19] While there is fossil evidence of earlier tyrannosauroids having feathers,[26][27] the evidence of such structures in tyrannosaurids is controversial as a study in 2017 from Bell and colleagues found no support in feathered integument in tyrannosaurids.[28] The study used skin impressions which are small, found widely dispersed across the post-cranium at different regions of the body with a pattern similar to crocodiles. Further the croc analogy Thomas Carr and colleagues in 2017 by studying the snout of Daspletosaurus suggested they have large scales with sensory sensory neuron pits under the skin.[29] This notion has been challenged from other authors who suggested a more lip-covering of the teeth.[30]

Distribution

The temporal range for tyrannosaurines went from almost 80.6 million years ago in the Campanian stage of the Late Cretaceous epoch to 66 million years ago in the Maastrichtian stage. Fossils have been found in different formations in what is now east Asia and western North America. While the Asian alioramins are the basal most group of the tyrannosaurines, the geographic placement of albertosaurines and other eutyrannosaurian tyrannosauroids found in North America suggests greatly the tyrannosaurines are North American in origin.[31]

Systematics

Prior to the 2010s, the relationships of the tyrannosaurines was best understood as Tyrannosaurus being a sister taxon to Tarbosaurus. These two genera in turn were the sister taxon to Daspletosaurus, follow by Alioramus. There was an alternative hypothesis from

Gregory Paul considered all tyrannosaurines at the time except Alioramus to be species of Tyrannosaurus.[34] In the second edition of The Princeton Field Guide to Dinosaurs published in 2016, Paul would continue this thought as well as including Bistahieversor, Teratophoneus, Lythronax, and Nanuqsaurus into the genus as well.[35] This multispecies Tyrannosaurus classification is, however, not widely accepted by most paleontologists.[33] In some phylogenetic studies Bistahieversor is nested within Tyrannosaurinae,[22][25] but it is most often recovered as the sister taxon to Tyrannosauridae instead.[31][33]

The

phylogenetic analyses performed by Voris et al. (2020):[33]

Eutyrannosauria

Dryptosaurus aquilunguis

Appalachiosaurus montgomeriensis

Bistahieversor sealeyi

Tyrannosauridae
Albertosaurinae

Gorgosaurus libratus

Albertosaurus sarcophagus

Tyrannosaurinae

As of 2023, at least three lineages of tyrannosaurines have been suggested.[33] The basalmost clade is the Alioramini. The second clade to diverge is the Teratophoneini, which comprises the American southwest taxa Dynamoterror, Lythronax, and Teratophoneus. They are sister to a third clade comprising Nanuqsaurus and the clade containing Daspletosaurini, which includes Daspletosaurus and Thanatotheristes, and the Tyrannosaurini, which includes Zhuchengtyrannus, Tarbosaurus, and Tyrannosaurus.[1]

The cladogram below displays the results of the strict consensus phylogenetic analysis performed by Scherer & Voiculescu-Holvad (2023), indicating the distinct lineages of tyrannosaurines.[1]

Tyrannosaurinae
Alioramini

Alioramus remotus

Alioramus altai

Qianzhousaurus sinensis

Teratophoneini

Dynamoterror dynastes

Teratophoneus curriei

Lythronax argestes

Nanuqsaurus hoglundi

Daspletosaurini

Thanatotheristes degrootorum

Daspletosaurus horneri

Daspletosaurus wilsoni

Daspletosaurus torosus

TMP 2001.36.1

Tyrannosaurini

Zhuchengtyrannus magnus

Tarbosaurus bataar

Tyrannosaurus rex

References

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  2. ^ Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix. Archived 2017-08-12 at the Wayback Machine
  3. ^ Breithaupt, B.H.; Southwell, E.H.; Matthews, N.A. (18 October 2005). "In Celebration of 100 years of Tyrannosaurus rex: Manospondylus gigas, Ornithomimus grandis, and Dynamosaurus imperiosus, the Earliest Discoveries of Tyrannosaurus rex in the West". Abstracts with Programs. 2005 Salt Lake City Annual Meeting. Vol. 37. Geological Society of America. p. 406. Archived from the original on 22 October 2019. Retrieved 8 October 2008.
  4. ^ Breithaup, BH; Southwell EH; Matthews NA (2006). "Dynamosaurus imperiosus and the earliest discoveries of Tyrannosaurus rex in Wyoming and the West". New Mexico Museum of Natural History and Science Bulletin. 35: 257–258.
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  8. ^ Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology. 1: 1–34.
  9. ^ Kurzanov, Sergei M. "A new carnosaur from the Late Cretaceous of Nogon-Tsav, Mongolia". The Joint Soviet-Mongolian Paleontological Expedition Transactions (in Russian). 3: 93–104.
  10. ^ Dong Zhiming (1977). "On the dinosaurian remains from Turpan, Xinjiang". Vertebrata PalAsiatica (in Chinese). 15: 59–66.
  11. ^ Carpenter, Ken. (1992). "Tyrannosaurids (Dinosauria) of Asia and North America". In Mateer, Niall J.; Peiji, Chen (eds.). Aspects of Nonmarine Cretaceous Geology. Beijing: China Ocean Press. pp. 250–268.
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  14. ^ Olshevsky, G. (1995). "The origin and evolution of the tyrannosaurids". Kyoryugaku Saizensen [Dino Frontline]. 9–10: 92–119.
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