Open Paleo

Tarchia

Maryańska, 1977 TAHRK-ee-a

From Mongolian tarkhi, "brain", combined with Latin suffix -ia — means "brainy one", referring to its presumed larger brain size compared to relatives

83.6–72.2 million years ago Campanian, Late Cretaceous
Late Cretaceous stages

Tarchia is a genus of herbivorous ankylosaurid dinosaur from the late Cretaceous of Mongolia.

Diagnosis

  1. Fenestra ovalis and cranial nerves IX-XI exit through a single external opening, with two separate exits for cranial nerve XII
  2. Accessory postorbital osteoderm fused to the skull roof
  3. Squamosal horn separated from the supraorbital boss by a postorbital fossa, with the accessory osteoderm seated within that fossa
  4. Large, deep braincase; foramen magnum taller than wide
  5. Nuchal osteoderms taller laterally than medially
  6. Occiput just visible in dorsal view and proportionally high in caudal view; postocular caputegulae absent

Species (3)

Tarchia kielanae Maryańska, 1977

Type species

Named for Professor Zofia Kielan-Jaworowska, the leader of the Polish-Mongolian expedition that discovered the holotype skull in 1970.

Holotype
ZPAL MgD-I/111 , Institute of Paleobiology, Polish Academy of Sciences
Material
Partial skull preserving most of one side of the postfrontal skull roof, including the sagittal midline and the braincase
Horizon
Baruungoyot Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Khulsan, Central Cliffs, site 6, Ömnögovi, Mongolia

Tarchia teresae Penkalski & Tumanova, 2017

Honors Teresa Maryańska, in recognition of work on Asian dinosaurs.

Holotype
PIN 3142/250 , Paleontological Institute, Russian Academy of Sciences
Material
Skull, mandibles, and postcranial material.
Horizon
Nemegt Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Hermiin Tsav I, Ömnögovi, Mongolia
Diagnosis
  1. Accessory postorbital osteoderm not fused to the skull roof (fused in T. kielanae).
  2. Quadrate and paroccipital process unfused.
  3. Skull roof over the postfrontal region deeply sculptured.
  4. Large, bifurcated opening for cranial nerves IX-XII.

Tarchia tumanovae Park et al., 2021

Honors Tatiana Tumanova, for contributions to understanding Mongolian ankylosaurs.

Holotype
MPC-D 100/1353 , Paleontological Center, Mongolian Academy of Sciences
Material
Well-preserved skull; dorsal, sacral, and caudal vertebrae; sixteen dorsal ribs; ilia; a partial ischium; free osteoderms; and a tail club.
Horizon
Nemegt Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Hermiin Tsav, Ömnögovi, Mongolia
Diagnosis
  1. Single, relatively bulbous internarial caputegulum that does not reach the rostral tip of the beak.
  2. Basioccipital foramen moderate-sized (unlike T. kielanae and T. teresae).
  3. Quadrate-quadratojugal region situated anteriorly (unlike T. teresae).
  4. Quadrate unfused to the exoccipital (fused in T. kielanae).
  5. Interpterygoid vacuity visible in occipital view (not visible in T. teresae).

References

  1. Maryańska, T. (1977). Ankylosauridae (Dinosauria) from Mongolia. Palaeontologia Polonica 37: 85-151. maryańska1977a
  2. Penkalski, P.; Tumanova, T. (2017). The cranial morphology and taxonomic status of Tarchia (Dinosauria: Ankylosauridae) from the Upper Cretaceous of Mongolia. Cretaceous Research 70: 117-127. Elsevier BV. doi:10.1016/j.cretres.2016.10.004

    Redescribes the holotype skull of Tarchia kielanae with a revised cranial diagnosis, holds it distinct from Saichania and Minotaurasaurus, and erects T. teresae on PIN 3142/250.

    penkalski2017a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026a
  4. Park, J. Y.; Lee, Y. N.; Kobayashi, Y.; Jacobs, L. L.; Barsbold, R.; Lee, H. J.; Kim, N.; Song, K. Y.; Polcyn, M. J. (2021). A new ankylosaurid from the Upper Cretaceous Nemegt Formation of Mongolia and implications for paleoecology of armoured dinosaurs. Scientific Reports 11: 22928. Springer Science and Business Media LLC. doi:10.1038/s41598-021-02273-4

    Erects Tarchia tumanovae on the partial skeleton MPC-D 100/1353 from the Nemegt Formation (Hermiin Tsav) of Mongolia.

    park2021a