Elaphrosaurus (/ɛˌlɑːfroʊˈsɔːrəs/ el-AH-froh-SOR-əs) is a genus of ceratosaurian theropod dinosaur that lived approximately 154 to 150 million years ago during the Late Jurassic Period in what is now Tanzania in Africa.

The specimen was collected by Werner Janensch, I. Salim, H. Reck, and Parkinson in 1910 in gray, green, red, sandy marl that was deposited during the Kimmeridgian stage of the Jurassic period, approximately 157 to 152 million years ago.

Although the neck of Elaphrosaurus was long, the thin zygapophyses and a lack of epipophyses on the cervical vertebrae indicate that it was much less flexible than those of other theropods and that it may have only supported a rather small skull.

These traits argue against Elaphrosaurus being a predator of large prey, and it was possibly omnivorous or herbivorous due to its close relation with Limusaurus.

According to Rauhut (2000), Elaphrosaurus can be distinguished based on the following characteristics: the cervical vertebrae possess thin latero-ventral laminae, bordering the posterior pleurocoel ventrally, the cervical vertebrae are strongly concave ventrally, with the ventral margin arching above the mid-height of the anterior articular facet at its highest point, the brevis fossa of the ilium is extremely widened, so that the brevis shelf forms an almost horizontal lateral flange, the distal end of the ischium is strongly expanded into a triangular boot.

Then, Elaphrosaurus was placed in the family Ornithomimidae by Franz Nopcsa in 1928 because of its light frame and the fact that its humerus is straight and slender, with a low deltopectoral crest.

[14][15] A re-study of the known fossil material, published in 2016, concluded that, due to characteristics of the scapulocoracod and metatarsals, Elaphrosaurus was actually an early member of the Noasauridae within Ceratosauria, and that it formed a distinct group with certain Asian noasaurids, which was named the Elaphrosaurinae.

[9] The following cladogram is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships of Elaphrosaurus among the noasaurids:[9] Abelisauridae Laevisuchus Deltadromeus Limusaurus

[3] However, newer studies support the idea that Elaphrosaurus was a herbivore or omnivore, owing to its close relation with Limusaurus and a neck which is much less flexible than those characteristic of carnivorous theropods.

[9] Studies suggest that the paleoenvironment of the Tendaguru Formation was a marginal marine environment with both non-marine faunal and floral content.

The Middle Dinosaur Member of the Tendaguru Formation has yielded the sauropods Giraffatitan, Australodocus, Janenschia, Tornieria and Dicraeosaurus, theropods similar to Allosaurus and Ceratosaurus, the carcharodontosaurid Veterupristisaurus, the stegosaurid Kentrosaurus and the iguanodontian Dysalotosaurus.