Alioramini

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

Description

Alioramins are medium-sized tyrannosaurids, reaching around in length. They have a more gracile body plan as compared to most other tyrannosaurines. Alioramins have rather shallow snouts, a trait that is rather rare among tyrannosaurs but can be found in the early tyrannosauroid, '' Xiongguanlong''. 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.

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). 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''.

Dinosaur researcher Gregory S. Paul has proposed a potential synonymy between '' Qianzhousaurus'' and '' Alioramus'', though others maintain them as separate genera. Alioramini is usually considered to be a part of the Tyrannosaurinae subfamily within the Tyrannosauridae family. This is supported by several features, including 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.
Below is a cladogram showing a basal placement of Alioramini within the Tyrannosaurinae, according to Brusatte & Carr (2016).

In their 2025 description of the non-tyrannosaurid tyrannosauroid '' Khankhuuluu'', Voris et al. (2025) proposed a novel arrangement of tyrannosaurine clades; suggesting that alioramins were a late-diverging clade more closely related to the similarly-aged Tyrannosaurini (''Zhuchengtyrannus'', '' Tarbosaurus'', and ''Tyrannosaurus'') than previously recognized. The authors reasoned that previous analyses had over-scored anatomical characters related to shallow skull morphology (a trait more common in non-tyrannosaurids and juvenile tyrannosaurids), which resulted in more basal positions for these species. They recognized seven cranial features that alioramins share with tyrannosaurins to the exclusion of other tyrannosaurines. They further argued that the juvenile-like proportions of alioramins were the result of paedomorphosis, rather than immaturity or being indicative of a basal phylogenetic position. These results are displayed in the cladogram below:

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).

Studies on the morphology of tyrannosauroid skulls suggest that alioramins experienced lower amounts of stress in their skulls when biting and feeding and that they likely did not utilize puncture-and-pull feeding like larger tyrannosaurines such as ''Tyrannosaurus'' and '' Daspletosaurus''.

See also

* Timeline of tyrannosaur research

References

External links

*

Skeletal reconstructions of ''Alioramus'' and ''Qianzhousaurus''
at Twitter

{{Taxonbar, from=Q17620750

Tyrannosauridae
Dinosaur tribes
Maastrichtian dinosaurs
Dinosaurs of Asia