Iliosuchus is a genus

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...

 known from Bathonian

Bathonian

In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...

–age (169.2 – 164.4 mya) rocks of 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 perhaps 1.5 metres (4.9 ft) long.

The only known fossils of this genus are three ilia

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 ,...

 (BMNH

BMNH

BMNH may refer to:*British Museum of Natural History, commonly known as Natural History Museum, in London, the United Kingdom*Beijing Museum of Natural History, in Beijing, China...

 R83, OUM J29780 and OUM J28971) from Stonesfield Slate

Stonesfield Slate

The Taynton Limestone Formation is a geological formation in the UK. It dates to the Middle Jurassic, mid-Bathonian stage.-Dinosaurs:-Pterosaurs:...

, Oxfordshire

Oxfordshire

Oxfordshire is a county in the South East region of England, bordering on Warwickshire and Northamptonshire , Buckinghamshire , Berkshire , Wiltshire and Gloucestershire ....

, 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...

. From 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...

 BMNH R83, Friedrich von Huene

Friedrich von Huene

Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...

 described and named the only species, I. incognitus, in 1932. The generic name is derived from the ilium and Greek Souchos, the crocodile god. The specific name means "unknown" in Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

. Another species, I. clevelandi, was proposed in 1976 by Peter Galton

Peter Galton

Peter M. Galton is a British vertebrate paleontologist working in America, who has to date written or co-written about a hundred papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosauropod dinosaurs.With Robert Bakker in a joint article...

, who assigned Stokesosaurus clevelandi

Stokesosaurus

Stokesosaurus is a genus of small , early tyrannosaur from the Late Jurassic period of Utah and England. It was named after Utah geologist William Lee Stokes...

to Iliosuchus, but this has not been followed.

The Iliosuchus ilia, very small with a length of nine to ten centimetres, have a vertical supra–acetabular

Acetabulum

The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...

 ridge on the surface, similar to tyrannosaurids and many other predatory dinosaurs belonging to the group Tetanurae

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:...

, including Piatnitzkysaurus

Piatnitzkysaurus

Piatnitzkysaurus is a genus of theropod dinosaur. It is known from the Canadon Asfalto Formation, Middle Jurassic of what is now Argentina. Once thought to be a basal carnosaur, it may instead be a megalosauroid...

and Megalosaurus

Megalosaurus

Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

. Such incomplete material is inadequate for accurate classification; nonetheless, Iliosuchus has sometimes been considered a tyrannosaurid ancestor. This is unlikely to be correct as the bones cannot be distinguished from small individuals of Megalosaurus, a megalosaurid. Whatever the case, Iliosuchus is not diagnostic and is therefore dubious

Nomen dubium

In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...

. If Iliosuchus incognitus is a tyrannosauroid, it would be the earliest one yet, preceding Guanlong

Guanlong

Guanlong was a genus of proceratosaurid tyrannosauroid dinosaur, one of the earliest known examples of the lineage.-Description and discovery:...

, otherwise the earliest recognized tyrannosauroid, by several million years.