Alioramini

Alioramins; Temporal range: Late Cretaceous, ; ~70–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Holotype skull of Alioramus altai
	Qianzhousaurus holotype skull
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Tyrannosauridae
Subfamily:	†Tyrannosaurinae
Clade:	†Alioramini; Olshevsky, 1995
Type species
	Alioramus remotus; Kurzanov 1976
Genera
	†Alioramus; †Qianzhousaurus; †Dryptosaurus?;

Alioramini is a clade of long-snouted tyrannosaurine tyrannosaurids from the Late Cretaceous epoch. It includes the tyrannosaurid genera Alioramus and Qianzhousaurus. Although tyrannosaurids are known from a variety of places around the globe, alioramins are currently restricted to Asia in mostly Maastrichtian strata.^[1] Many of the fossils attributed to Alioramini are not from fully developed individuals.^[2]

Description

Alioramins are medium-sized tyrannosaurids, reaching around 5–7 m (16–23 ft) in length. They have a more gracile body plan as compared to most other tyrannosaurines.^[3]^[4] Alioramins have rather shallow snouts, a trait that is rather rare among tyrannosaurs but can be found in the early tyrannosauroid, Xiongguanlong.^[5] Alioramins are unique when compared to contemporary tyrannosaurs from the same time, such as Tarbosaurus and Tyrannosaurus, because most of the longer snouted tyrannosauroids, such as Xiongguanlong, were found in deposits dating to earlier times during the Cretaceous. Members of the alioramins also have an elongated maxillary fenestra. Besides their elongated snouts, perhaps another major trait that makes alioramins stand out is their nasal ridges. While most other tyrannosaurids have nasal ridges, the nasal ridges in alioramins are pronounced and discrete. They form well developed bumps on the surface of the nasal bones, forming their nasal crest. Within the dentary bone, alioramins have 18 or more teeth. ^[6]^[1]

Classification

The name Alioramini was first coined in 1995 by George Olshevsky only to contain the at-the-time uncertain Alioramus. Olshevsky classified Alioramini within the base of Tyrannosaurinae and considered it to be a tribe or a "paratribe" (a name for a paraphyletic tribe, emphasizing Olshevsky's view that the hypothetical common ancestor of tyrannosaurids could be classified as an alioramin).^[7] Alioramini were first described as a clade by Junchang Lü and colleagues in 2014, who defined it as a branch-based clade containing all tyrannosaurids more related to Alioramus than to Albertosaurus, Proceratosaurus, and Tyrannosaurus. Hence, the clade Alioramini consists of three species, namely Alioramus altai, Alioramus remotus, and Qianzhousaurus sinensis.^[1]

Some researchers have tried to synonymize Qianzhousaurus with Alioramus,^[8] but many others maintain that they are separate genera. Alioramini is usually considered to be a part of the Tyrannosaurinae subfamily within the Tyrannosauridae family; however, some phylogenetic studies find them to be outside the Tyrannosauridae. Alioramini is a part of Tyrannosaurinae, based on several features. These features include a maxillary process of the premaxilla that points upwards; the deep joint surface in the maxilla conceals certain features related to tooth roots; the particular shape of the lacrimal, mostly hidden from view; and an ectopterygoid with a pneumatic recess that possesses a distinctive round or triangular shape.^[9] Dryptosaurus, usually placed as a basal eutyrannosaur is found to be a member of Alioramini under a Bayesian analysis in 2016 Carr and Brusatte paper, but this is the only time in the 2016 paper an analysis yields such a result with the rest of the paper placing Dryptosaurus in its usual position.^[10]

Below is a cladogram showing the placement of Alioramini within the Tyrannosaurinae, according to Brusatte & Carr (2016).^[10]

Tyrannosauridae

Albertosaurinae

	Gorgosaurus libratus

	Albertosaurus sarcophagus

Tyrannosaurinae

Alioramini

Qianzhousaurus sinensis

	Alioramus altai

	Alioramus remotus

	Nanuqsaurus hoglundi

	Teratophoneus curriei

Lythronax argestes

	Daspletosaurus horneri

	Daspletosaurus torosus

Zhuchengtyrannus magnus

	Tarbosaurus bataar

	Tyrannosaurus rex

Another cladogram showing the relationships of Alioramini by Loewen et al. (2013) places Alioramini outside of the Tyrannosauridae.^[11]

Tyrannosauroidea

Proceratosauridae

	Proceratosaurus bradleyi

	Kileskus aristotocus

	Guanlong wucaii

Sinotyrannus kazuoensis

	Juratyrant langhami

	Stokesosaurus clevelandi

Dilong paradoxus

Eotyrannus lengi

Bagaraatan ostromi

Raptorex kriegsteini

Dryptosaurus aquilunguis

	Alectrosaurus olseni

	Xiongguanlong baimoensis

Appalachiosaurus montgomeriensis

	Alioramus altai

	Alioramus remotus

Tyrannosauridae

Paleobiology

Alioramins, due to their relatively gracile build and long snouts, were likely specialized in hunting small-sized prey with quick turns. Such feeding strategies may have avoided direct competition with other tyrannosaurids. In contrast to robust tyrannosaurids, whose juveniles underwent drastic changes in their skull, the characteristic elongated snout morphology of alioramins was likely maintained throughout their ontogeny (growth).^[12]^[13]

Studies on the morphology of tyrannosauroid skulls published in August, 2024 suggest that alioramins experienced lower amounts of stress in their skulls when biting and feeding. The same study indicates that these theropods likely did not utilize puncture-and-pull feeding like larger tyrannosaur genera such as Tyrannosaurus and Daspletosaurus.^[14]