''Chilantaisaurus'' (" lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of large

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

, possibly a neovenatorid or a primitive coelurosaur, from the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Ulansuhai Formation of China (

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded ...

age, about 92 million years ago). The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

, ''C. tashuikouensis'', was described by Hu in 1964.

Description

''Chilantaisaurus'' was a large theropod, estimated as weighing between and . In 2010, Brusatte et al. estimated it to weigh , based on femur length measurements. However, considering that greater femoral circumference indicates the greater capacity to withstand greater locomotor loads (not greater body mass), the 2020 study moderated the body mass of the holotype at . It is estimated to be around to long.

Classification

Hu considered ''Chilantaisaurus'' to be a

carnosaur Carnosauria is an extinct large group of predatory dinosaurs that lived during the Jurassic and Cretaceous periods. Starting from the 1990s, scientists have discovered some very large carnosaurs in the carcharodontosaurid family, such as ''Gig ...

related to ''

Allosaurus ''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch ( Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alludi ...

'', though some subsequent studies suggested that it may be a spinosauroid, possibly a primitive member of the spinosaurid family (Sereno, 1998; Chure, 2000; Rauhut, 2001) because it had large claws on the forelimbs thought to be unique to that group. Other studies suggested that it could be a member of an alternate offshoot of neotetanuran theropods, with some similarities to allosauroids, spinosauroids, and

coelurosauria Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, ty ...

ns. A 2009 study noted that it was difficult to rule out the possibility that ''Chilantaisaurus'' was the same animal as the carnosaur '' Shaochilong'', which is from the same geological formation. However, they did note an enormous size difference between the two. Further study by Benson, Carrano and Brusatte found that it was not as closely related to ''Shaochilong'' as first thought, but that it was a carnosaur (of the family

Neovenatoridae Neovenatoridae is a proposed clade of carcharodontosaurian dinosaurs uniting some primitive members of the group such as ''Neovenator'' with the Megaraptora, a group of theropods with controversial affinities. Other studies recover megaraptoran ...

), closely related to ''Allosaurus'' as Hu had initially thought. Phylogenetic analysis published by Porfiri et al. in 2018 recovered ''Chilantaisaurus'' as a primitive

Chilantaisaurus-Tianjin Natural History Museum

Several species have been described based on very poor remains. The species ''"Chilantaisaurus" sibiricus'' (previously informally known as either ''

? sibiricus'' or '' Antrodemus? sibiricus'') is based on a single distal

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

discovered in 1915 in the Turginskaya Svita of the Buryat Autonomous Soviet Socialist Republic,

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...

, dating to the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

periods (

Berriasian In the geological timescale, the Berriasian is an age/ stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years a ...

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by t ...

stages). It is poorly described, so its relationships cannot be accurately determined (Chure, 2000) and its placement as a species of ''Chilantaisaurus'' is highly questionable. "Chilantaisaurus" ''maortuensis'' was reclassified as ''Shaochilong maortuensis'' in 2009.Brusatte, S., Benson, R., Chure, D., Xu, X., Sullivan, C., and Hone, D. (2009). "The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids." ''Naturwissenschaften'', An additional species named in 1979, "Chilantaisaurus" ''zheziangensis'', based on bones from the foot and a partial tibia, is actually a therizinosaur taxon. The cladogram below follows a 2016 analysis by Sebastián Apesteguía, Nathan D. Smith, Rubén Juarez Valieri, and Peter J. Makovicky based on the dataset of Carrano et al. (2012).

References

External links

* {{Taxonbar, from=Q134633 Prehistoric coelurosaurs Neovenatorids Late Cretaceous dinosaurs of Asia Fossil taxa described in 1964