Temporal range: Late Cretaceous
Image 1567-Siats-meekerorum
An artist's interpretation of Siats meekerorum
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebra
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Carcharodontosauridae
Genus: Siats
Zanno & Makovicky, 2013
Species: S. meekerorum
Binomial name
Siats meekerorum
Zanno & Makovicky, 2013

Siats meekerorum was the apex predator of the Cenomanian Stage. It's name is a combination of two factors; the word Siats, comes from a man eating monster in Ute Mythology, whereas Meekerorum honors the late geologist John Caldwell Meeker, who bequeathed a fund for paleontological research.[1][2][3][4][5][6]

The holotype specimen is found in Utah, Cedar Mountain formation (Mussentuchit Member), which also gave us the well-known Deinonychus. The holotype is also the only known specimen from this genus, described by paleontologist Lindsay E. Zanno in year 2009. It is one of the largest theropod dinosaurs known from North America. [7][8][9][10]

Skeleton includes traces of wide, crocodilian - shaped teeth. Dr. Zanno thinks that is a clue that giant crocodiles. Today, Siats is generally known for being the fourth to third largest terrestrial carnivore North America has ever known. It was initially classified as a megaraptoran, a group with extremelly controversial relations.[11][12]


First when Zanno and Makovicky discovered the skeleton, they thought it belongs to carcharodontosaurid type of dinosaur, possibly close related to Acrocanthosaurus or Shaochilong. Most phylogenetic analysis suggests that it was a carcharodontosaurid (Neovenatorid?).[13] The paper describing a juvenile Megaraptor suggested that Siats is not a megaraptoran, and instead is likely a neovenatorid, as it shares several traits with Neovenator, but differs from megaraptorans in the structure of its dorsal vertebrae, ilium, and fibula.[14]

A subsequent analysis conducted by Coria and Currie (2016), which even placed megaraptorans as neovenatorids, still placed Siats and Chilantaisaurus as neovenatorids outside of Megaraptora. The discovery of Siats also reveals that allosauroids did not yield dominance in North America to tyrannosauroids until the very late periods of Cretaceous.[15][16][17][18]

Siats is known from the holotype FMNH PR 2716, a partial postcranial skeleton housed at the Field Museum of Natural History, Chicago. FMNH PR 2716 consists of five dorsal and eight caudal vertebrae, a chevron, partial right ilium, ischium and fibula, a partial left tibia, and several right and left pedal phalanges. FMNH PR 2716 was discovered by Lindsay Zanno, as a part of a 2008 expedition of the Field Museum led by Peter Makovicky. The bones were first seen protruding out of a hillside, prompting the excavation.[19]


It was collected between 2008 and 2010 from the Mussentuchit Member of the Cedar Mountain Formation, in Emery County of Utah, dating to the early Cenomanian stage of the Late Cretaceous, approximately 94.5 million years ago.



By Justice Duncan (BlueTheDakotaraptor)

Holotype specimen is about 9-11 m long, over 3 m tall and weighs 4-5 tonnes. However, the description paper of Siats states that the holotype is skeletally immature.[20]

  • Hypothetical adults could most likely reach sizes of over 12 m in length and over 5 tonnes in weight, what surely makes this Theropod one of the largest predators in the North America!



Dinosaurs of the Mussentuchit Member by Lamborlobator

Siats meekerorum was found in the Mussentuchit Member of the Cedar Mountain Formation.

Siats by mariolanzas

Siats meekerorum by Mario Lanzas

It lived alongside ankylosaurs, the giant Sauropod Abydosaurus, Deinonychus, the small tyrannosaur Moros and ornithischians such as Tenontosaurus and Eolambia. Due being recovered as carcharodontosaurid, Siats very likely mainly gone after Eolambia, Tenontosaurus and Abydosaurus.[21]


  1. https://www.nature.com/articles/ncomms3827
  2. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0157973&from=article_link
  3. https://www.wired.com/2013/11/new-dinosaur-siats/
  4. https://www.youtube.com/watch?v=tCZQGmb_pZk
  5. https://www.sci.news/paleontology/science-siats-meekerorum-dinosaur-utah-01567.html
  6. https://a-dinosaur-a-day.com/post/92962296760/siats-meekerorum
  7. https://edition.cnn.com/2013/11/22/us/siats-meekerorum-dinosour-discovered/index.html
  8. https://dinoanimals.com/dinosaurs/siats-large-cretaceous-theropod/
  9. https://www.chicagotribune.com/2013/11/22/graphic-facts-on-siats-meekerorum/
  10. https://www.fieldmuseum.org/blog/siats-meekerorum
  11. https://thekidshouldseethis.com/post/68078445754
  12. https://dinodiyar.wordpress.com/tag/siats-meekerorum/
  13. https://sciences.ncsu.edu/news/dinosaur-discovery-2/
  14. https://www.fossilcrates.com/pages/siatsmeekerorum
  15. https://www.nbcnews.com/sciencemain/meet-gigantic-carnivore-kept-t-rex-down-2d11642435
  16. https://www.eurekalert.org/news-releases/471108
  17. https://blog.everythingdinosaur.com/blog/_archives/2013/11/23/unravelling-the-apex-predators-of-the-cretaceous-before-tyrannosaurs.html
  18. https://news.ncsu.edu/2013/11/new-predator-dinosaur-siats/
  19. https://www.theverge.com/2013/11/22/5132928/siats-meekerorum-new-dinosaur-discovery-utah
  20. https://www.deviantart.com/bluethedakotaraptor/art/Siats-meekerorum-820886118
  21. https://www.voanews.com/a/new-meat-eating-dinosaur-discovered-in-utah/1797400.html