| Timurlengia | |
|---|---|
 | |
| Cast ofholotype braincase,National Museum of Natural History | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Superfamily: | †Tyrannosauroidea |
| Clade: | †Pantyrannosauria |
| Genus: | †Timurlengia Brusatte et al.,2016 |
| Species: | †T. euotica |
| Binomial name | |
| †Timurlengia euotica Brusatte et al., 2016 | |
Timurlengia is an extinctgenus oftyrannosauroid dinosaurs known from the earlyLate Cretaceous (Turonian age)Bissekty Formation of theKyzylkum Desert in Uzbekistan. The genus contains asingle species,Timurlengia euotica, named in 2016 based on a braincase and numerous single bones of many individuals.
Timurlengia is part of a grade of early-diverging tyrannosauroids preceding the later and largertyrannosaurids such asTyrannosaurus. As such, it helps elucidate the early evolution of the anatomy of these animals. In particular, it shows that these species developed their large heads and sophisticated hearing abilities before their large bodies, which only happened in the last 20 million years of the clade's evolution.Timurlengia was likely a pursuit hunter that could hear low-frequency sounds based on the shape of itsear canal.
From 1944 onwards, tyrannosauroid fossil material consisting of single bones has been described from theBissekty Formation by Soviet or Russian researchers.[1] In 2004 an international team discovered abraincase. The braincase was housed at the Zoological Institute of the Russian Academy of Sciences, where tyrannosaur expertStephen L. Brusatte, identified it as a new species in 2014.[2]
In 2016, Stephen L. Brusatte, Alexander Averianov,Hans-Dieter Sues, Amy Muir, and Ian B. Butler named and described the type speciesTimurlengia euotica. The genus is named afterTimurlenk, founder of theTimurid Empire in Central Asia. Thespecific nameeuotica is Greek for "well-eared",[1] because detailedCT scans show thatTimurlengia had a well-developed inner ear for hearing low-frequency sounds.[2]
The species was based on theholotype specimen, ZIN PH 1146/16, an isolated braincase. Other bones described in 2012 that do not belong to a single individual were referred to the species.[3] These include the specimens ZIN PH 854/16: the right half of a braincase; ZIN PH 676/16: a rightmaxilla; ZIN PH 2330/16: a left frontal bone; ZIN PH 2296/16: a left quadrate; ZIN PH 15/16: a piece of a right dentary; ZIN PH 1239/16: a right articular with angular; ZIN PH 671/16: an anterior cervical vertebra; USNM 538131: a posterior cervical vertebra; USNM 538132: theneural arch of anterior dorsal vertebra; CCMGE 432/12457: a mid-dorsal vertebra; ZIN PH 951/16: an anterior tail vertebra; ZIN PH 120/16: a mid-caudal vertebra; ZIN PH 507/16: a posterior caudal vertebra; ZINPH 619/16: a hand claw; and USNM 538167: a toe claw. These fossils were referred to a single tyrannosauroidtaxon because no other tyrannosauroid is known from the Bissekty Formation.[1] However, specimen ZIN PH 2330/16 was suggested to be a dromaeosaurid instead by Voris et al. (2025).[4]
The holotype specimen belongs to a subadult about 3–4 m (9.8–13.1 ft) long and weighing around 170–270 kg (370–600 lb).[1][5] ZIN PH 1239/16 represents a larger, adult individual.[1]
In 2016, several distinguishing traits were established, all relating to the holotype braincase. Thesupraoccipital bone has a diamond-shaped process pointing below and not reaching the upper rim of theforamen magnum. The basioccipital has very short basal tubers, only attaining a third of the height of theoccipital condyle. Theoval window and the ear vestibule form a funnel-shaped recess and has a wide exit on the side wall of the braincase. Theinner ear is large with prominentsemicircular canals.[1]
Timurlengia was placed in theTyrannosauroidea, in a basal position, as a possiblesister species ofXiongguanlong. Together they may represent aclade of long-snouted forms that might have been thesister group of theTyrannosauridae.[1]
The genus is important in showing how earlier small tyrannosauroids evolved into the large Tyrannosauridae likeTyrannosaurus, typical of theLate Cretaceous period of Asia and North America. The species is not believed to be a direct ancestor ofTyrannosaurus.[6]Timurlengia lived ninety million years ago, in the middle-lateTuronian age of the early Late Cretaceous, right before the rise of the advanced tyrannosaurids. There had been a twenty million year "tyrannosaur gap" in the fossil records of the tyrannosauroid timeline, between the small "marginal hunters" and the "apex predators" of the tyrannosaurid group. The discovery ofTimurlengia has filled that gap.[1]Timurlengia reveals that tyrannosaurs had yet to achieve huge size at this time but had already evolved key brain and sensory features of the gigantic latest Cretaceous species. These features were originally thought to be unique to big tyrannosaurs, as they evolved into large animals.[7] Tyrannosaurs apparently developed huge size rapidly during the late Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses which first evolved at a smaller body size.[8]Timurlengia's small size indicates that tyrannosaurs only evolved their large size in the last twenty million years of their evolution.[9] It is unknown what precisely triggered the size increase.[1]
The braincase ofTimurlengia shows that tyrannosaurs likely developed their advancedhead first, as hypothesised by Hans-Dieter Sues, one of the fossil's describers.Timurlengia’sskull, though much smaller than that ofTyrannosaurus, shows a sophisticatedbrain that would have led to keeneyesight,smell andhearing. At the time tyrannosaurs were developing acute senses andcognitive abilities, other large meat-eating dinosaurs such as theCarnosauria were disappearing from the environment or dying out, creating a vacant niche, allowing tyrannosaurs to become apex predators.[6][10] The head ofTimurlengia is far lesspneumatised than that of the larger tyrannosaurids; the increased airspaces with the later forms might have been an adaptation to lighten the skull or to increase hearing ability.[1]
Below is acladogram based on the results of aphylogenetic analysis by Wolfe et al. (2019), illustrating on the placement ofTimurlengia.[11]
Based on the known material,Timurlengia was likely a pursuit hunter with blade-like teeth for slicing through meat.[6] The robustness of the semicircular inner ear canals might be related to greater agility.Timurlengia has a longcochlear duct, with the same height as thelabyrinth, an adaptation to hearing low-frequency sounds. This might be an indication that the animal used low calls to communicate within the species.[1]
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