Temporal range: Late Cretaceous
|An artist's interpretation of Siats meekerorum|
Zanno & Makovicky, 2013
Zanno & Makovicky, 2013
Siats meekerorum, meaning Man-Eating Monster, was the apex predator of the Cenomanian Stage. It was named after a man eating monster and the Meeker family, who are museum donors. 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. 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 largest terrestrial carnivore North America has ever known. It was initially classified as a megaraptoran, a group with controversial relations. The group may be tyrannosauroids, allosauroids, or basal coelurosaurs.
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?). 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. 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 late Cretaceous
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. 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.
Holotype specimen is about 9-11 m long, over 3 m tall and weighs 4-5 tonnes (4.7 tonnes according to a volumetric analysis by Toxic Midget), what's pretty large to neovenatorid standards. However, the description paper of Siats states that the holotype is skeletally immature. 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.
Siats meekerorum was found in the Mussentuchit Member of the Cedar Mountain Formation. 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.