Stokesosaurus
Encyclopedia
Stokesosaurus is a genus
of small (around 3 to 4 meters (10-13 ft) in length), early tyrannosaur from the Late Jurassic
period of Utah
and England
. It was named after Utah geologist William Lee Stokes. Remains possibly referable to Stokesosaurus have been recovered from stratigraphic zone 2 of the Morrison Formation
, dated to the late Kimmeridgian
age, about 152 million years ago.
The holotype
(UUVP
2938) consists of a hip bone—originally thought to belong to the possible early tyrannosaur Iliosuchus
,—as well as several vertebrae, and a partial braincase
. Another ilium
referred to this dinosaur is lost but may actually belong to the related Aviatyrannis
, and a premaxilla
thought to belong to Iliosuchus is actually from Tanycolagreus
.
A second species, Stokesosaurus langhami, was described by Roger Benson in 2008 based on a partial skeleton. The skeleton consists of an "associated partial skeleton represented by a complete pelvis" as well as a partially complete leg, as well as neck, back, and tail vertebrae. This second skeleton was discovered in 1984 in Dorset. The specimen was mentioned in several papers, but was not formally described until 2008. The new species was named in honor of Peter Langham, who collected the specimen. The new specimen was discovered in strata dating from the Tithonian
, the final stage of the Late Jurassic
, indicating the fossil is around 150 million years old.
Stokesosaurus and Tanycolagreus are about the same size, and it is possible that the latter is a junior synonym of the former. However, the ilium (the best known element of Stokesosaurus) of Tanycolagreus has never been recovered, making direct comparison difficult.
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 small (around 3 to 4 meters (10-13 ft) in length), early tyrannosaur from the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
period of Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
and England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. It was named after Utah geologist William Lee Stokes. Remains possibly referable to Stokesosaurus have been recovered from stratigraphic zone 2 of the Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
, dated to the late Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....
age, about 152 million years ago.
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...
(UUVP
University of Utah
The University of Utah, also known as the U or the U of U, is a public, coeducational research university in Salt Lake City, Utah, United States. The university was established in 1850 as the University of Deseret by the General Assembly of the provisional State of Deseret, making it Utah's oldest...
2938) consists of a hip bone—originally thought to belong to the possible early tyrannosaur Iliosuchus
Iliosuchus
Iliosuchus is a genus of theropod dinosaur known from Bathonian–age rocks of England. It was perhaps long....
,—as well as several vertebrae, and a partial braincase
Endocast
An endocast is the internal cast of a hollow object, often specifically used for an endocasts of the cranial vault. Endocasts can be man-made for examining the properties of a hollow, inaccessible space, or occur naturally through fossilisation....
. Another ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
referred to this dinosaur is lost but may actually belong to the related Aviatyrannis
Aviatyrannis
Aviatyrannis is a genus of tyrannosauroid dinosaur from the Kimmeridgian stage of the Late Jurassic found in Portugal. It was described by Oliver Rauhut in 2003. The name means "Jurassic grandmother tyrant"...
, and a premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
thought to belong to Iliosuchus is actually from Tanycolagreus
Tanycolagreus
Tanycolagreus is a genus of coelurid theropod from the Late Jurassic of North America. The holotype is a partial skeleton recovered from the Bone Cabin Quarry West locality, Albany County, Wyoming, from the Morrison Formation...
.
A second species, Stokesosaurus langhami, was described by Roger Benson in 2008 based on a partial skeleton. The skeleton consists of an "associated partial skeleton represented by a complete pelvis" as well as a partially complete leg, as well as neck, back, and tail vertebrae. This second skeleton was discovered in 1984 in Dorset. The specimen was mentioned in several papers, but was not formally described until 2008. The new species was named in honor of Peter Langham, who collected the specimen. The new specimen was discovered in strata dating from the Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
, the final stage of the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
, indicating the fossil is around 150 million years old.
Stokesosaurus and Tanycolagreus are about the same size, and it is possible that the latter is a junior synonym of the former. However, the ilium (the best known element of Stokesosaurus) of Tanycolagreus has never been recovered, making direct comparison difficult.