Bagaraatan

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title: "Bagaraatan" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["tyrannosauroidea", "dinosaur-genera", "maastrichtian-dinosaurs", "nemegt-formation", "fossil-taxa-described-in-1996", "taxa-named-by-halszka-osmólska", "dinosaurs-of-mongolia"] description: "Extinct genus of theropod dinosaurs" topic_path: "general/tyrannosauroidea" source: "https://en.wikipedia.org/wiki/Bagaraatan" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Extinct genus of theropod dinosaurs ::

| fossil_range = Late Cretaceous, | image = Bagaraatan jaw.png | image_caption = Lower jaw bones | taxon = Bagaraatan | authority = Osmólska, 1996 | type_species = Bagaraatan ostromi | type_species_authority = Osmólska, 1996 Bagaraatan (/'ba-ɣa-raa-tan/ meaning 'small' baɣa + 'carnivorous animal, beast of prey' araatan in Mongolian) is a genus of theropod dinosaur from the Late Cretaceous period of what is now the Nemegt Formation of Mongolia. It may have been a small predatory dinosaur measuring around 3 to 4 m in length.

History

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/70/Bagaraatan_outline.jpg" caption="1996 skeletal diagram showing holotype and assigned elements that are now known to belong to a different species"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/9/91/Bagaraatan.jpg" caption="Partial mandible"] ::

The type species, B. ostromi, was described by Halszka Osmólska in 1996. Initially, the post-cranial (ZPAL MgD-I/108) skeleton had been described as "bird-like", while the skull was noted to exhibit features of several different theropod groups.

The material that warranted this conclusion was later found to be a chimaera of two non-avian dinosaurs, with some of the post-crania (hand bones, left femur, tibiotarsus, and rib) being referred to an indeterminate caenagnathid, possibly Elmisaurus. The material that is considered the holotype, which includes the mandible, axial skeleton, pelvis, and one pedal phalanx, likely indicates that Bagaraatan is an indeterminate tyrannosaurid. Similarities between the material and young specimens of Tyrannosaurus and Tarbosaurus indicate that the holotype represents a juvenile tyrannosaurid, one of the smallest currently known.

Classification

::figure[src="https://upload.wikimedia.org/wikipedia/commons/9/9e/Bagaraatan_size_diagram.png" caption="Size compared to a human"] ::

Holtz classified Bagaraatan as a basal tyrannosauroid, Coria identified it as a troodontid, and Rauhut placed it in Maniraptora. Mark Loewen et al. placed it in basal Tyrannosauroidea, agreeing with the placement by Holtz.

Below is the cladogram by Loewen et al. in 2013.

In their 2024 reassessment of Bagaraatan, Słowiak, Brusatte & Szczygielski determined that the initial material referred to Bagaraatan is chimaeric. They suggested that the material recognized as the holotype can more confidently be identified as a member of the Tyrannosauridae or a closely related tyrannosauroid. When tested in a phylogenetic analysis, Bagaraatan was recovered in a polytomy with derived tyrannosauroids within the Tyrannosauridae. However, they caution that its exact phylogenetic position remains uncertain since juvenile specimens tend to be recovered in more basal positions than adults of the same species. Their results are shown in the cladogram below:

|{{clade |1=Sinotyrannus [[File:Sinotyrannus TD.png|85px]] |2=Yutyrannus [[File:Yutyrannus TD.png|85px]] |3=Proceratosaurus |4=Guanlong [[File:Guanlong wucaii by durbed.jpg|80px]] |5=Kileskus [[File:Kileskus.png|85px]] |6={{clade |1=Suskityrannus |2={{clade |1=Timurlengia [[File:Timurlengia.jpg|80px]] |2={{clade |1=Xiongguanlong [[File:Xiongguanlong_baimoensis.png|80px]] |2={{clade |1=Dryptosaurus [[File:Dryptosaurus TD.png|85px]] |2={{clade |1=Raptorex |label2=Tyrannosauridae |2={{clade |1=Bagaraatan |2=Bistahieversor |3=Qianzhousaurus [[File:Qianzhousaurus sinensis by PaleoGeek.png|85px]] |4=Alioramus altai [[File:Alioramus altai.jpg|75px]] |5=Alioramus remotus [[File:Alioramus Life Restoration.jpg|85px]] |6=Appalachiosaurus [[File:Appalachiosaurus montgomeriensis.jpg|85px]] |7=Albertosaurinae [[File:Gorgosaurus.png|85px]] |8=Tyrannosaurinae [[File:Tyrannosaurus-rex-Profile-steveoc86 (coloured).png|85px]]

References

Sources

• Osmolska, H. (1996). "An unusual theropod dinosaur from the Late Cretaceous Nemegt Formation of Mongolia". Acta Palaeontologica Polonica 41; 1-38 https://www.app.pan.pl/article/item/app41-001.html

References

1. (2024-02-16). "Reassessment of the enigmatic Late Cretaceous theropod dinosaur, ''Bagaraatan ostromi''". [[Zoological Journal of the Linnean Society]].
2. O. W. M. Rauhut (2003). The interrelationships and evolution of basal theropod dinosaurs. ''Special Papers in Palaeontology'' '''69''': 1-213.
3. (2013). "Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans". [[PLoS ONE]].

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::