Monolophosaurus
Encyclopedia
Monolophosaurus was a genus
of theropod dinosaur
from the Middle Jurassic
(about 168-161 Ma) of the Shishugou Formation
in what is now Xinjiang
, China
. It was named for the single crest on top of its skull. The type
and only known individual is estimated at 5 metres (16.4 ft). The area that Monolophosaurus was found showed signs of water, so it is possible that this dinosaur lived on the shore of lakes or ocean. The Monolophosaurus jiangi IVP 84019 had its 10th and possibly 11th neural spines fractured. The tenth is fused to the eleventh. A series of parallel ridges on one of the specimen's dentaries may represent tooth marks.
A nearly complete skeleton
was unearthed in 1984. At first, before description in the scientific literature, it was known in the press as "Jiangjunmiaosaurus", a nomen nudum
.
In 1993 Zhao and Currie named the type species
Monolophosaurus jiangi; the species name refers to Jiangjunmiao ("an abandoned desert inn") near which the holotype
IVPP 84019 was found. Monolophosaurus was originally termed a "megalosaur
" and has often since been suggested to be an allosauroid
. Carr (2006) even suggested that the "proceratosaurid
" "tyrannosauroid
" Guanlong
was a subadult Monolophosaurus and therefore an "allosauroid
", by noting both taxa have a large, thin, and fenestrated midline crest, but this is probably not the case.
Smith et al. (2007) was the first publication to find Monolophosaurus to be a non-neotetanuran tetanuran, by noting many characters previously thought to be exclusive of Allosauroidea to have a more wider distribution. Also, Zhao et al. (2009) noted various primitive features of the skeleton suggesting that Monolophosaurus could be one of the most basal tetanuran
dinosaurs instead. Benson (2008, 2010) placed Monolophosaurus in a clade
with Chuandongocoelurus
that is more basal than Megalosauridae and Spinosauridae
in the Megalosauroidea. Latter, Benson et al. (2010) found the Chuandongocoelurus/Monolophosaurus clade to be outside of Megalosauroidea and Neotetanurae, near the base of Tetanurae.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Middle Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
(about 168-161 Ma) of the Shishugou Formation
Shishugou Formation
The Shishugou Formation is a geological formation in Xinjiang, China, whose strata date back to the Late Jurassic period. Dinosaur remains are among the fossils that have been recovered from the formation....
in what is now Xinjiang
Xinjiang
Xinjiang is an autonomous region of the People's Republic of China. It is the largest Chinese administrative division and spans over 1.6 million km2...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. It was named for the single crest on top of its skull. The type
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
and only known individual is estimated at 5 metres (16.4 ft). The area that Monolophosaurus was found showed signs of water, so it is possible that this dinosaur lived on the shore of lakes or ocean. The Monolophosaurus jiangi IVP 84019 had its 10th and possibly 11th neural spines fractured. The tenth is fused to the eleventh. A series of parallel ridges on one of the specimen's dentaries may represent tooth marks.
Discovery and classification
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
was unearthed in 1984. At first, before description in the scientific literature, it was known in the press as "Jiangjunmiaosaurus", a nomen nudum
Nomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...
.
In 1993 Zhao and Currie named the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
Monolophosaurus jiangi; the species name refers to Jiangjunmiao ("an abandoned desert inn") near which the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
IVPP 84019 was found. Monolophosaurus was originally termed a "megalosaur
Megalosauroidea
Megalosauroidea is a group of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period.-Classification:...
" and has often since been suggested to be an allosauroid
Allosauroidea
Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Sinraptoridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae...
. Carr (2006) even suggested that the "proceratosaurid
Proceratosauridae
Proceratosauridae is a family or clade of theropod dinosaurs, probably belonging to the tyrannosaur lineage. It was first named in 2010 by Oliver Rauhut and colleagues in their re-evaluation of the type genus, Proceratosaurus...
" "tyrannosauroid
Tyrannosauroidea
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...
" Guanlong
Guanlong
Guanlong was a genus of proceratosaurid tyrannosauroid dinosaur, one of the earliest known examples of the lineage.-Description and discovery:...
was a subadult Monolophosaurus and therefore an "allosauroid
Allosauroidea
Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Sinraptoridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae...
", by noting both taxa have a large, thin, and fenestrated midline crest, but this is probably not the case.
Smith et al. (2007) was the first publication to find Monolophosaurus to be a non-neotetanuran tetanuran, by noting many characters previously thought to be exclusive of Allosauroidea to have a more wider distribution. Also, Zhao et al. (2009) noted various primitive features of the skeleton suggesting that Monolophosaurus could be one of the most basal tetanuran
Tetanurae
Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early or middle Jurassic Period.-Definition:...
dinosaurs instead. Benson (2008, 2010) placed Monolophosaurus in a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with Chuandongocoelurus
Chuandongocoelurus
Chuandongocoelurus named after the Chuandong in Sichuan Province, China, was a genus of tetanuran theropod dinosaur first described by Chinese paleontologist He in 1984...
that is more basal than Megalosauridae and Spinosauridae
Spinosauridae
Spinosauridae is a family of specialised theropod dinosaurs. Members of this family were large, bipedal predators with elongated, crocodile-like skulls, sporting conical teeth with no or only very tiny serrations. The front dentary teeth fanned out, giving the animal a characteristic look...
in the Megalosauroidea. Latter, Benson et al. (2010) found the Chuandongocoelurus/Monolophosaurus clade to be outside of Megalosauroidea and Neotetanurae, near the base of Tetanurae.
External links
- Monolophosaurus in the Dino Directory, The Natural History Museum, London.