Elaphrosaurus 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...

 from the 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....

 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...

 of Tanzania

Tanzania

The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

. Elaphrosaurus was probably a ceratosaur about 6 meters (20 ft) long. Suggestions that it is a late surviving coelophysoid have been entertained but are generally dismissed. It was first described as a coelurid

Coeluridae

Coeluridae is a historically polyphyletic family of generally small, carnivorous dinosaurs from the late Jurassic Period...

. At the time, Coeluridae was a wastebasket taxon for small theropods. Later, it was thought that Elaphrosaurus was related to ornithomimids

Ornithomimosauria

The Ornithomimosauria, ornithomimosaurs or ostrich dinosaurs were theropod dinosaurs which bore a superficial resemblance to modern ostriches. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia...

, but this has also lost favor in preference to a ceratosaurian identity.

A skeleton was found in the Tendaguru Beds

Tendaguru

The Tendaguru Beds are a fossil-rich formation in Tanzania. It has been considered the richest of Late Jurassic strata in Africa. Continental reconstructions show Tendaguru to have been in the southern hemisphere during the Late Jurassic. Tendaguru is similar to the Morrison Formation except in...

 of Tanzania, which also yielded Giraffatitan

Giraffatitan

Giraffatitan, meaning "giraffe titan", is a genus of sauropod dinosaur that lived during the late Jurassic Period . It was originally named as an African species of Brachiosaurus...

, Allosaurus

Allosaurus

Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period . The name Allosaurus means "different lizard". It is derived from the Greek /allos and /sauros...

, and Kentrosaurus

Kentrosaurus

Kentrosaurus is a genus of stegosaurid dinosaur from the Late Jurassic of Tanzania. Its fossils have been found only in the Tendaguru Formation of Tanzania, dated to the Kimmeridgian stage, between about 155.7 ± 4 Ma and 150.8 ± 4 Ma . Apparently, all finds belong to one species, K...

. A related animal, perhaps the same genus, was found in 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...

. Few theropod skeletons have been found, most discoveries being fragments. Material from the Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 of Niger

Niger

Niger , officially named the Republic of Niger, is a landlocked country in Western Africa, named after the Niger River. It borders Nigeria and Benin to the south, Burkina Faso and Mali to the west, Algeria and Libya to the north and Chad to the east...

 was named E. gautieri in 1960, but it has since been renamed Spinostropheus

Spinostropheus

Spinostropheus is a genus of small ceratosaurian dinosaur that lived in the late Jurassic period of Niger. Once thought to be a species closely related to the abelisaurs , subsequent studies have confirmed the original interpretation as a basal ceratosaur closely related to Elaphrosaurus...

by Sereno et al. (2004). What is known about Elaphrosaurus mostly comes from a single nearly complete skeleton. No skull has been found.
It was long and slender, with a long neck. It was about 6.2 meters (20 ft) long, 1.46 meters (4.79 ft) tall at the hip, and weighed about 210 kilograms (460 lb

Pound (mass)

The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

). The tibia

Tibia

The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

 (shin bone) of Elaphrosaurus was considerably longer than its femur

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

(thigh bone), which indicates that it could probably run very fast. It is also possibly present in stratigraphic zones 2-4 of the Morrison Formation.