Elaphrosaurus Temporal range:Late Jurassic (Kimmeridgian toTithonian),155–145 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Holotype skeleton mounted (skull, hands and other elements speculative and likely outdated),Natural History Museum of Berlin
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Noasauridae
Subfamily:	†Elaphrosaurinae
Genus:	†Elaphrosaurus Janensch, 1920
Species:	†E. bambergi
Binomial name
†Elaphrosaurus bambergi Janensch, 1920

Elaphrosaurus (/ɛˌlɑːfroʊˈsɔːrəs/el-AH-froh-SOR-əs) is agenus ofceratosauriantheropoddinosaur that lived approximately 155 to 145million years ago during theLate Jurassic Period in what is nowTanzania inAfrica.Elaphrosaurus was a medium-sized but lightly built member of the group that could grow up to 6.2 m (20 ft) long. Morphologically, this dinosaur is significant in two ways. Firstly, it has a relatively long body but is very shallow-chested for a theropod of its size. Secondly, it has very short hindlimbs in comparison with its body. Phylogenetic analyses indicate that this genus is likely aceratosaur. Earlier suggestions that it is a late survivingcoelophysoid have been examined but generally dismissed.Elaphrosaurus is currently believed to be a very close relative ofLimusaurus, an unusual beaked ceratosaurian which may have been either herbivorous or omnivorous.

The type specimen ofElaphrosaurus bambergi HMN Gr.S. 38–44 was recovered in the Middle Dinosaur Member of theTendaguru Formation ofLindi Region in Tanzania. 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 theKimmeridgianstage of theJurassic period, approximately 157 to 152 million years ago. This specimen is housed in the collection of theNatural History Museum of Berlin,Germany.

Elaphrosaurus was described and named byWerner Janensch in1920 and thetype species isElaphrosaurus bambergi. The genus nameElaphrosaurus is derived from theGreek wordselaphros (ελαφρός) meaning "light to bear" as in "light-footed", a reference to its presumed high running speed and "sauros" (σαῦρος) meaning "lizard";^[1] thus, "light-footed lizard". Thespecific name honours the industrialistPaul Bamberg for his financial support of the Tendagaru expeditions.^[2]

HMN Gr.S. 38–44 consists of 18 presacral vertebrae, 5 sacral vertebrae, 20 caudal vertebrae, apelvic girdle, a nearly complete left hindlimb (missing only some phalanges), several isolated metacarpals, and ahumerus. In 1925, Janesch referred two rib fragments, dorsal vertebrae, and a manualphalanx he believed to be phalanx II-2. However, the referred vertebrae has been lost and the manual phalanx (now considered to be phalanx I-1) cannot be evaluated as belonging toElaphrosaurus. In 1929, he also referred toElaphrosaurus bothscapulocoracoids, two more rib fragments, and aradius (although the radius, being proportionally long and from a differentstratigraphic horizon, likely does not belong to this species). Many bones were damaged bycalcite encrustation and reconstructed with plaster, although only the left scapulocoracoid was significantly deformed.

A related animal, perhaps the same genus, was found in stratigraphic zones 2–4 of theMorrison Formation.^[3][4] Few theropod skeletons have been found, most discoveries being fragments.

Dinosaur footprints from theNiger Republic and fromBeit Zayit were attributed toElaphrosaurus.^[5][6] This assignment is considered inconclusive.

It also known from the Upper dinosaur member of the Tendaguru formation.^[7]

Elaphrosaurus was long and slender, with a long neck. What is known aboutElaphrosaurus mostly comes from a single nearly complete skeleton and no skull has been found. It was distinctive among theropods for being short-legged for its length. Paul (1988) noted that this was the longest-bodied and shallowest-chestedtheropod that he had examined.^[3]Elaphrosaurus was about 6–6.2 m (19.7–20.3 ft) long, 1.46 m (4.8 ft) tall at the hip, and weighed about 200–210 kg (440–460 lb).^[3][8] Thetibia (shin bone) ofElaphrosaurus, measured 608 mm was considerably longer than itsfemur (thigh bone) that measured 520 mm, and themetatarsals were 74% the length of the femur. These proportions, also shared by someornithomimosaurs, likely indicate cursorial habits.^[9] Its long tail ended with a rare downward bend which may be unrelated totaphonomy. Although the neck ofElaphrosaurus was long, the thinzygapophyses and a lack ofepipophyses 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 againstElaphrosaurus being a predator of large prey, and it was possibly omnivorous or herbivorous due to its close relation withLimusaurus.^[10]

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism. According to Rauhut (2000),Elaphrosaurus can be distinguished based on the following characteristics: thecervical 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, thebrevis fossa of the ilium is extremely widened, so that thebrevis shelf forms an almost horizontal lateral flange, the distal end of theischium is strongly expanded into a triangular boot.

An emended diagnosis in Rauhut and Carrano's 2016 study added thatElaphrosaurus could uniquely be distinguished by pronounced ventrolateral laminae at the posterior ends of the cervical vertebrae, no cervical epipophyses (especially unique amongabelisauroids), the distal end of metacarpal II offset ventrally from its shaft by a distinct step, the proximal end of metatarsal IV almost 2.5 times deeper anteroposteriorly than wide transversely, and a very short ascending process of theastragalus (if identified correctly).^[10]

Elaphrosaurus was first described by Janensch as acoelurosaurian.^[2] At the time, Coelurosauria was awastebasket taxon for small theropods. Then,Elaphrosaurus was placed in the familyOrnithomimidae byFranz Nopcsa in 1928 because of its light frame and the fact that itshumerus is straight and slender, with a low deltopectoral crest.^[11] Janensch himself rejected this assignment, believing any resemblances could plausibly be explained byconvergent evolution. By the middle of the twentieth century,Elaphrosaurus was usually seen as a member of theCoeluridae. However, Nopcsa's hypothesis was revived byDale Alan Russell in 1972,^[12] and confirmed byPeter Malcolm Galton in 1982.^[13] In 1988Gregory S. Paul remarked that upon closer examination its limbs approximate those ofCoelophysis and suggested a position in theCoelophysidae.^[3] Nevertheless, in 1990 Barsbold,Teresa Maryańska and Osmólska and other researchers still classified it as anornithomimid.^[14] More recent work by Carrano and Sampson (2008) and Carrano et al. (2012) assignElaphrosaurus to theCeratosauria.^[15][16] A re-study of the known fossil material, published in 2016, concluded that, due to characteristics of the scapulocoracoid and metatarsals,Elaphrosaurus was actually an early member of theNoasauridae within Ceratosauria, and that it formed a distinct group with certain Asian noasaurids, which was named theElaphrosaurinae.^[10]

The followingcladogram is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships ofElaphrosaurus among the noasaurids:^[10]

The following material was assigned toElaphrosaurus over the years, but further study revealed that these assignments were dubious:

• Elaphrosaurus iguidiensis, was described byAlbert-Félix de Lapparent in 1960,^[17] and the material was collected inAlgeria,Libya andNiger in EarlyCretaceous sediments. The material consists of over forty teeth, a manualungual, eight caudal vertebrae, a distalfemur fragment, and a completetibia measuring 350 mm. These specimens originated in three different localities and do not appear to belong to the same species.
• Elaphrosaurus gautieri, was first described by de Lapparent in 1960,^[17] and the material was collected at theTiouraren Formation in Niger in Middle-LateJurassic sediments. This material, a partial skeleton, has since been renamedSpinostropheus gautieri by Serenoet al. (2004).^[18]
• Elaphrosaurus philtippettensis, subsequentlyElaphrosaurus philtippettorum, was erected by Stephan Pickering^[19][20] in 1995 based on USNM 5737, which consists of a tibia, a humerus, some metatarsals, and the distal portion of a fragmentarypubic bones recovered from theMorrison Formation of Colorado. Research by Carpenter et al. (2005) concluded that these fossils are notceratosaurian and are likely referable to thecoelurid theropodTanycolagreus. It is named after visual effects supervisorPhil Tippett.
• Elaphrosaurus agilis, was a renaming by Dale Russell in 1980 ofCoelurus agilis, originally named byOthniel Charles Marsh in 1884.^[21] The species is based on a pair of fused pubic bones that were by Marsh believed to represent a much larger version of the type speciesCoelurus fragilis.John Ostrom (1980) confirmedCharles Whitney Gilmore's earlier position thatCoelurus agilis was synonymous withCoelurus fragilis. This means thatElaphrosaurus agilis is actually the same animal asCoelurus fragilis, itsjunior synonym.
• Elaphrosaurus sp. USNM 8415, was discovered in 1883 and first referred to theornithopodDryosaurus. It was later referred toElaphrosaurus by Galton in 1982, based on remains recovered at the Morrison Formation of Colorado. This material, which is clearly ceratosaurian, does not bear any morphology that specifically ties it toElaphrosaurus. Current knowledge limits the placement of this material to Ceratosauriaincertae sedis.^[22]
• Elaphrosaurus sp. DMNH 36284, was referred to this genus by Chure^[23] in 2001, based on the proximal portion of a fragmentary righttibia from the Brushy Basin Member of the Morrison Formation. Phylogenetic analysis by Carrano and Sampson (2008) showed that it was not basalceratosaurian, but instead resembled the leg bone of anabelisauroid theropod that has yet to be formally described.^[22]

Paul (1988) noted thatElaphrosaurus bambergi was too small to prey on the sauropods and stegosaurs present in its paleoenvironment, and suggested instead that it likely hunted the small and swiftornithopod herbivores.^[3] However, newer studies support the idea thatElaphrosaurus was a herbivore or omnivore, owing to its close relation withLimusaurus and a neck which is much less flexible than those characteristic of carnivorous theropods.^[10]

Studies suggest that thepaleoenvironment 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 sauropodsGiraffatitan,Australodocus,Janenschia,Tornieria andDicraeosaurus, theropods similar toAllosaurus andCeratosaurus, thecarcharodontosauridVeterupristisaurus, thestegosauridKentrosaurus and theiguanodontianDysalotosaurus. Dinosaurs shared this paleoenvironment with pterosaurs likePterodactylus andRhamphorhynchus, as well as with early mammals.

• Timeline of ceratosaur research

• Noasauridae
• Dinosaur genera
• Kimmeridgian dinosaurs
• Tendaguru Formation
• Fossil taxa described in 1920
• Taxa named by Werner Janensch
• Dinosaurs of Tanzania

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