Alioramini

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Alioramins
Temporal range: Late Cretaceous,
~70–66  Ma
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Alioramus altai skull at AMNH.jpg
Holotype skull of Alioramus altai
Qianzhousaurus holotype skull.jpg
Holotype skull of Qianzhousaurus
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Superfamily: Tyrannosauroidea
Family: Tyrannosauridae
Subfamily: Tyrannosaurinae
Tribe: Alioramini
Olshevsky, 1995
Type species
Alioramus remotus
Kurzanov, 1976
Genera

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. [1] Many of the fossils attributed to Alioramini are not from fully developed individuals. [2]

Contents

Description

Size of three alioramin species compared to a human Alioramini Scale.svg
Size of three alioramin species compared to a human

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]

Dinosaur researcher Gregory S. Paul has proposed a potential synonymy between Qianzhousaurus and Alioramus , [8] 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. [9] Below is a cladogram showing a basal placement of Alioramini within the Tyrannosaurinae, according to Brusatte & Carr (2016). [10]

Tyrannosauridae

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: [11]

Eutyrannosauria

Paleobiology

Life restoration of Alioramus with the caenagnathid Nomingia in the Nemegt Formation paleoenvironment Alioramus and Nomingia.jpg
Life restoration of Alioramus with the caenagnathid Nomingia in the Nemegt Formation paleoenvironment

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 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 . [14]

See also

References

  1. 1 2 3 Lü, J.; Yi, L.; Brusatte, S. L.; Yang, L.; Li, H.; Chen, L. (2014). "A new clade of Asian Late Cretaceous long-snouted tyrannosaurids" (PDF). Nature Communications. 5 (3788): 3788. Bibcode:2014NatCo...5.3788L. doi: 10.1038/ncomms4788 . PMID   24807588.
  2. Holtz, Thomas R. (2004). "Tyrannosauroidea". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (Second ed.). Berkeley: University of California Press. pp. 111–136. ISBN   978-0-520-24209-8.
  3. Molina-Pérez, R.; Larramendi, A. (2016). "List of Theropods". Dinosaur Facts and Figures: The Theropods and Other Dinosauriformes. Princeton: Princeton University Press. p. 266. doi:10.1515/9780691190594. ISBN   9788416641154. JSTOR   j.cdb2hnszb. S2CID   198839986.
  4. Xing, L.; Niu, K.; Lockley, M. G.; Klein, H.; Romilo, A.; Scott Persons IV, W.; Brusatte, S. L. (2022). "A probable tyrannosaurid track from the Upper Cretaceous of southern China". Science Bulletin. 64 (16): 1136−1139. Bibcode:2019SciBu..64.1136X. doi:10.1016/j.scib.2019.06.013. hdl: 20.500.11820/05d88bb3-8039-426c-88bf-cfb6f08608e7 . PMID   36659682. S2CID   197083656.
  5. Li, Daqing; Norell, Mark A.; Gao, Ke-Qin; Smith, Nathan D.; Makovicky, Peter J. (2009). "A longirostrine tyrannosauroid from the Early Cretaceous of China". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 183–190. doi:10.1098/rspb.2009.0249. PMC   2842666 . PMID   19386654.
  6. Brusatte, S. L.; Carr, T. D.; Norell, M. A. (2012). "The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria, Theropoda) from the late Cretaceous of Mongolia". American Museum Novitates (366): 1−197. doi:10.1206/770.1. hdl: 2246/6162 . S2CID   84550111.
  7. Olshevsky, G. (1995). "The origin and evolution of the tyrannosaurids, Part 2". Kyoryugaku Saizensen. 10: 75–99.
  8. Paul, Gregory S. (2016). The Princeton field guide to dinosaurs. Princeton field guides (2nd ed.). Princeton: Princeton university press. ISBN   978-0-691-16766-4.
  9. Brusatte, Stephen L.; Norell, Mark A.; Carr, Thomas D.; Erickson, Gregory M.; Hutchinson, John R.; Balanoff, Amy M.; Bever, Gabe S.; Choiniere, Jonah N.; Makovicky, Peter J.; Xu, Xing (2010-09-17). "Tyrannosaur Paleobiology: New Research on Ancient Exemplar Organisms" (PDF). Science. 329 (5998): 1481–1485. Bibcode:2010Sci...329.1481B. doi:10.1126/science.1193304. ISSN   0036-8075. PMID   20847260.
  10. Brusatte, Stephen L.; Carr, Thomas D. (2016-02-02). "The phylogeny and evolutionary history of tyrannosauroid dinosaurs". Scientific Reports. 6 (1): 20252. Bibcode:2016NatSR...620252B. doi:10.1038/srep20252. ISSN   2045-2322. PMC   4735739 . PMID   26830019.
  11. Voris, Jared T.; Zelenitsky, Darla K.; Kobayashi, Yoshitsugu; Modesto, Sean P.; Therrien, François; Tsutsumi, Hiroki; Chinzorig, Tsogtbaatar; Tsogtbaatar, Khishigjav (2025-06-11). "A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria". Nature . doi:10.1038/s41586-025-08964-6. ISSN   0028-0836. PMID   40500434.
  12. Brusatte, S. L.; Carr, T. D.; Erickson, G. M.; Bever, G. S.; Norell, M. A. (2009). "A long-snouted, multihorned tyrannosaurid from the Late Cretaceous of Mongolia". Proceedings of the National Academy of Sciences. 106 (41): 17261–17266. doi: 10.1073/pnas.0906911106 . PMC   2765207 . PMID   19805035.
  13. Foster, W.; Brusatte, S. L.; Carr, T. D.; Williamson, T. E.; Yi, L.; Lü, J. (2022). "The cranial anatomy of the long-snouted tyrannosaurid dinosaur Qianzhousaurus sinensis from the Upper Cretaceous of China". Journal of Vertebrate Paleontology. 41 (4): e1999251. doi: 10.1080/02724634.2021.1999251 . hdl: 20.500.11820/85571b5c-0e63-4caa-963a-f16a42514319 . S2CID   246799243.
  14. Rowe, Andre J.; Rayfield, Emily J. (September 2024). "Morphological evolution and functional consequences of giantism in tyrannosauroid dinosaurs". iScience. 27 (9): 110679. Bibcode:2024iSci...27k0679R. doi:10.1016/j.isci.2024.110679. ISSN   2589-0042. PMC   11387897 . PMID   39262785.