| Tyrannosaurinae | |
|---|---|
 | |
| Skull ofAlioramus. | |
_2_(15157270200).jpg) | |
| Skull ofTyrannosaurus. | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Superfamily: | †Tyrannosauroidea |
| Family: | †Tyrannosauridae |
| Subfamily: | †Tyrannosaurinae Osborn, 1906 |
| Type genus | |
| †Tyrannosaurus Osborn, 1905 | |
| Subgroups[4] | |
Tyrannosaurinae (ortyrannosaurines) is one of the two extinct subfamilies ofTyrannosauridae, afamily ofcoelurosauriantheropods that consists of at least three tribes and severalgenera. All fossils of these genera have been found in theLate Cretaceous deposits of westernNorth America and eastAsia. Compared to the related subfamilyAlbertosaurinae, tyrannosaurines overall are more robust and larger though the alioramins were gracile by comparison. This subfamily also includesLythronax, one of the oldest known tyrannosaurid genera, as well as the youngest and most famous member of the group,Tyrannosaurus rex.
The first remains of tyrannosaurids were uncovered during expeditions led by theGeological Survey of Canada, which located numerous scattered teeth. These distinctive dinosaur teeth were given the nameDeinodon ("terrible tooth") byJoseph Leidy in 1856. In 1892Edward Drinker Cope described more tyrannosaur material in the form of isolated vertebrae, and gave this animal the nameManospondylus 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.[5] Later in 1905Henry Fairfield Osborn described two tyrannosaur specimens that had been collected inMontana andWyoming during a 1902 expedition of theAmerican Museum of Natural History, led byBarnum Brown. Initially, Osborn considered these to be distinct species. The first, he namedDynamosaurus 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 thatDynamosaurus had been found first, the nameTyrannosaurus had appeared one page earlier in his original article describing both specimens. Therefore, according to theInternational Code of Zoological Nomenclature (ICZN), the nameTyrannosaurus was used.[6]
The second described representative of the tyrannosaurines,Tarbosaurus (originally described as an Asiatic representative ofTyrannosaurus) was in 1955 after a large skull was recovered in a jointSoviet-Mongolian expedition to theGobi Desert in the MongolianÖmnögovi Province in 1946. Theholotype was named asTyrannosaurus bataar byEvgeny Maleev asTyrannosaurus bataar.[7] The genusTarbosaurus 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 asTarbosaurus efremovi.[8] It was only in 1965 thatTy. bataar andTa. efremovi were the same species, the latter being a younger animal, and distinct fromTyrannosaurus recognized byA.K. Rozhdestvensky who recombined the species asTarbosaurus bataar.[9]
In the 1970s saw the description of two genera. In 1970 saw the publication ofDaspletosaurus, with the holotypeCMN 8506 consisting of a partial skeleton including the skull, the shoulder, a forelimb, thepelvis, a femur and all of thevertebrae from the neck, torso and hip, as well as the first eleven tail vertebrae. It was discovered in 1921 nearSteveville, Alberta, byCharles Mortram Sternberg, who thought it was a new species ofGorgosaurus, but was found to be a new genus byDale Russell using the aforementioned CMN 8506.[10] The second,Alioramus, described in 1976 bySergei Kurzanov which the holotype (PIN 3141/1) is a partial skull associated with threemetatarsals 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 ofBayankhongor,Nemegt Formation.[11]
From 1977 to 2009 saw the publications of several genera. In Asia they includeShanshanosaurus (1977),[12]Maleevosaurus (1992),[13] andRaptorex (2009),[14] while in North America sawNanotyrannus (1988),[15]Dinotyrannus andStygivenator (1995).[16] These genera, however are controversial as the remains of these animals are immature or juvenile individuals. With the exception ofNanotyrannus (now recovered as an eutyrannosaurian outside Tyrannosauridae) and possiblyRaptorex,[17][18] it is widely assumed that the Asian specimens are early growth stages ofTarbosaurus,[19][20][21] whereas the North American specimens are those ofTyrannosaurus.[22][23]
Valid genera would not be named until the 2010s, where in 2011 announced the publication ofTeratophoneus by Thomas D. Carr and colleagues. The fossils were first found in theKaiparowits Formation of southern Utah. Later, fossils from the same formation were discovered and identified as the genus.Argon-argon radiometric dating indicates that the Kaiparowits Formation was deposited between 76.1 and 74.0 million years ago, during theCampanian stage of theLate Cretaceous period. This date means thatTeratophoneus lived in the middle of the Campanian stage of the Late Cretaceous.[24] In the same yearZhuchengtyrannus was named by David W. E. Hone and colleagues based on the holotype ZCDM V0031, a nearly complete right maxilla and associated left dentary (lower jaw, both with teeth) housed at Zhucheng Dinosaur Museum.[25] In 2014 cameNanuqsaurus, the northern most tyrannosaurid found inPrince Creek Formation of theNorth Slope of Alaska, United States.[26][27] In the same year also announcedQianzhousaurus known from a partial sub-adult individual consisting of a nearly complete skull with the lower jaws missing allteeth (lost during fossilization), 9cervical vertebrae, 3dorsal vertebrae, 18 caudal vertebrae, bothscapulocoracoids, partialilia, and the left hindlimb compromising thefemur,tibia,fibula,astragalus withcalcaneum, andmetatarsals III and IV.[28]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 theWahweap Formation of theGrand Staircase–Escalante National Monument.[29]
In comparison to the albertosaurines, tyrannosaurines were more heavily built and larger. The alioramin genera ofQianzhousaurus andAlioramus, however, were the exception, as they were more comparable in built to albertosaurines and have longirostrine snouts.[28] Like albertosaurines, tyrannosaurines also hadheterodont dentition, large heads design to catch and kill their prey, and short didactyl arms. Based on the growth stages ofTyrannosaurus (and possiblyTarbosaurus[21]), 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.[23] While there is fossil evidence of earlier tyrannosauroids having feathers,[30][31] 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.[32] 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 ofDaspletosaurus suggested they have large scales with sensory sensory neuron pits under the skin.[33] This notion has been challenged from other authors who suggested a more lip-covering of the teeth.[34]
The temporal range for tyrannosaurines went from almost 80.6 million years ago in theCampanian stage of theLate Cretaceous epoch to 66 million years ago in theMaastrichtian 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 othereutyrannosaurian tyrannosauroids found in North America suggests greatly the tyrannosaurines are North American in origin.[35]
Prior to the 2010s, the relationships of the tyrannosaurines was best understood asTyrannosaurus being a sister taxon toTarbosaurus. These two genera in turn were the sister taxon toDaspletosaurus, follow byAlioramus. There was an alternative hypothesis fromPhil Currie and colleagues (2003) who suggestedDaspletosaurus to be more closely related toTarbosaurus andAlioramus than toTyrannosaurus based on cranial features.[36] This relationship, however, has not been found in more recent studies.[24][26][29][35][37] In 1988Gregory Paul considered all tyrannosaurines at the time exceptAlioramus to be species ofTyrannosaurus.[38] In the second edition ofThe Princeton Field Guide to Dinosaurs published in 2016, Paul would continue this thought as well as includingBistahieversor,Teratophoneus,Lythronax, andNanuqsaurus into the genus as well.[39] This multispeciesTyrannosaurus classification is, however, not widely accepted by most paleontologists.[37] In some phylogenetic studiesBistahieversor is nested within Tyrannosaurinae,[26][29] but it is most often recovered as the sister taxon toTyrannosauridae instead.[35][37]
Thecladogram below displays the position of the Tyrannosaurinae withinEutyrannosauria and Tyrannosauridae, based on the results ofphylogenetic analyses performed by Voriset al. (2020):[37]
As of 2023, at least three lineages of tyrannosaurines have been suggested.[37] The basalmost clade is theAlioramini. The second clade to diverge is theTeratophoneini, which comprises the American southwest taxaDynamoterror,Lythronax, andTeratophoneus. They are sister to a third clade comprisingNanuqsaurus and the clade containingDaspletosaurini, which includesDaspletosaurus andThanatotheristes, and theTyrannosaurini, which includesZhuchengtyrannus,Tarbosaurus, andTyrannosaurus.[2]
The cladogram below displays the results of the strict consensus phylogenetic analysis performed by Scherer & Voiculescu-Holvad (2023), indicating the distinct lineages of tyrannosaurines.[2]
| Tyrannosaurinae | |
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