''Elaphrosaurus'' ( ) 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. ''Elaphrosaurus'' was a medium-sized but lightly built member of the group that could grow up to 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 a ceratosaur. Earlier suggestions that it is a late surviving coelophysoid have been examined but generally dismissed. ''Elaphrosaurus'' is currently believed to be a very close relative of '' Limusaurus'', an unusual beaked ceratosaurian which may have been either herbivorous or omnivorous.

Discovery

The type specimen of ''Elaphrosaurus bambergi'' HMN Gr.S. 38–44 was recovered in the Middle Dinosaur Member of the Tendaguru Formation of

Lindi Region Lindi Region (''Mkoa wa Lindi'' in Swahili) is one of Tanzania's 31 administrative regions. The region covers an area of . The region is comparable in size to the combined land area of the nation state of Sri Lanka. The regional capital is the m ...

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 the Kimmeridgian stage of the Jurassic period, approximately 157 to 152 million years ago. This specimen is housed in the collection of the Natural History Museum of Berlin, Germany. ''Elaphrosaurus'' was described and named by Werner Janensch in

1920 Events January * January 1 ** Polish–Soviet War in 1920: The Russian Red Army increases its troops along the Polish border from 4 divisions to 20. ** Kauniainen, completely surrounded by the city of Espoo, secedes from Espoo as its own ma ...

and the type species is ''Elaphrosaurus bambergi''. The genus name ''Elaphrosaurus'' is derived from the Greek words ' () meaning "light to bear" as in "light-footed", a reference to its presumed high running speed and "" (') meaning "lizard"; thus, "light-footed lizard". The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honours the industrialist

Paul Bamberg Paul may refer to: *Paul (given name), a given name (includes a list of people with that name) * Paul (surname), a list of people People Christianity *Paul the Apostle (AD c.5–c.64/65), also known as Saul of Tarsus or Saint Paul, early Chri ...

for his financial support of the Tendagaru expeditions. HMN Gr.S. 38–44 consists of 18 presacral vertebrae, 5 sacral vertebrae, 20 caudal vertebrae, a pelvic girdle, a nearly complete left hindlimb (missing only some phalanges), several isolated metacarpals, and a

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

. In 1925, Janesch referred two rib fragments, dorsal vertebrae, and a manual phalanx 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 to ''Elaphrosaurus.'' In 1929, he also referred to ''Elaphrosaurus'' both scapulocoracoids, two more rib fragments, and a radius (although the radius, being proportionally long and from a different stratigraphic horizon, likely does not belong to this species). Many bones were damaged by

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

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 the

Morrison Formation The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...

.Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their World''. Indiana University Press. pp. 327–329. Few theropod skeletons have been found, most discoveries being fragments. Dinosaur footprints from the

Niger Republic ) , official_languages = , languages_type = National languagesBeit Zayit were attributed to ''Elaphrosaurus''. This assignment is considered inconclusive.

Description

''Elaphrosaurus'' was long and slender, with a long neck. What is known about ''Elaphrosaurus'' 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-chested theropod that he had examined. ''Elaphrosaurus'' was about long, tall at the hip, and weighed about . In 2016 another estimation listed it at 7.5 meters (24.6 feet) long, 2.1 meters tall (6.9 feet) at the hips and 210 kg (460 pounds) in weight. The tibia (shin bone) of ''Elaphrosaurus'', measured 608 mm was considerably longer than its femur (thigh bone) that measured 520 mm, and the metatarsals were 74% the length of the femur. These proportions, also shared by some

ornithomimosaurs Ornithomimosauria ("bird-mimic lizards") are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia (now Asia, Europe and North ...

, likely indicate cursorial habits. Its long tail ended with a rare downward bend which may be unrelated to taphonomy. Although the neck of ''Elaphrosaurus'' was long, the thin zygapophyses and a lack of

epipophyses Epipophyses are bony projections of the cervical vertebrae found in archosauromorphs, particularly dinosaurs (including some basal birds). These paired processes sit above the postzygapophyses on the rear of the vertebral neural arch. Their morp ...

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''.

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: the

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

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 The ischium () form ...

is strongly expanded into a triangular boot. An emended diagnosis in Rauhut and Carrano's 2016 study added that ''Elaphrosaurus'' could uniquely be distinguished by pronounced ventrolateral laminae at the posterior ends of the cervical vertebrae, no cervical epipophyses (especially unique among abelisauroids), 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 the astragalus (if identified correctly).

Classification

Elaphrosaurus mount MfN Berlin 2018 neck detail

Elaphrosaurus mount MfN Berlin 2018 limb detail

''Elaphrosaurus'' was first described by Janensch as a coelurosaurian. At the time, Coelurosauria was a wastebasket taxon for small theropods. Then, ''Elaphrosaurus'' was placed in the family Ornithomimidae by

Franz Nopcsa Franz may refer to: People * Franz (given name) * Franz (surname) Places * Franz (crater), a lunar crater * Franz, Ontario, a railway junction and unorganized town in Canada * Franz Lake, in the state of Washington, United States – see ...

in 1928 because of its light frame and the fact that its

is straight and slender, with a low deltopectoral crest. Janensch himself rejected this assignment, believing any resemblances could plausibly be explained by convergent evolution. By the middle of the twentieth century, ''Elaphrosaurus'' was usually seen as a member of the Coeluridae. However, Nopcsa's hypothesis was revived by

Dale Alan Russell Dale Alan Russell (27 December 1937 – 21 December 2019) was an American-Canadian geologist and palaeontologist. Throughout his career Russell worked as the Curator of Fossil Vertebrates at the Canadian Museum of Nature, Research Professor at ...

in 1972, and confirmed by

Peter Malcolm Galton Peter Malcolm Galton (born 14 March 1942 in London) is a British vertebrate paleontologist who has to date written or co-written about 190 papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosa ...

in 1982. In 1988 Gregory S. Paul remarked that upon closer examination its limbs approximate those of '' Coelophysis'' and suggested a position in the Coelophysidae. Nevertheless, in 1990 Barsbold, Teresa Maryańska and Osmólska and other researchers still classified it as an ornithomimid. More recent work by Carrano and Sampson (2008) and Carrano et al. (2012) assign ''Elaphrosaurus'' to the Ceratosauria. 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 Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed Abelisauridae, abelisaurids, although most noasaurids had much more traditional body types generally simila ...

.Rauhut, O.W.M., and Carrano, M.T. (2016). The theropod dinosaur ''Elaphrosaurus bambergi'' Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania. ''Zoological Journal of the Linnean Society'', (advance online publication) The following cladogram is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships of ''Elaphrosaurus'' among the noasaurids:

Formerly assigned species

The following material was assigned to ''Elaphrosaurus'' over the years, but further study revealed that these assignments were dubious: * ''Elaphrosaurus iguidiensis'', was described by Albert-Félix de Lapparent in 1960,Lapparent, A.-F. 1960. Les dinosauriens du "Continental intercalaire" du Sahara central. Mémoires de la Société Géologique de France. 88A 1–57. and the material was collected in Algeria, Libya and Niger in Early Cretaceous sediments. The material consists of over forty teeth, a manual ungual, eight caudal vertebrae, a distal femur fragment, and a complete tibia 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, and the material was collected at the Tiouraren Formation in Niger in Middle-Late Jurassic sediments. This material, a partial skeleton, has since been renamed ''

Spinostropheus ''Spinostropheus'' is a genus of carnivorous ceratosaurian theropod dinosaur that lived in the Middle Jurassic period and has been found in the Tiouraren Formation, Niger. The type species, type and only species is ''S. gautieri''. History of d ...

gautieri'' by Sereno ''et al.'' (2004). * ''Elaphrosaurus philtippettensis'', subsequently ''Elaphrosaurus philtippettorum'', was erected by Stephan Pickering in 1995 based on USNM 5737, which consists of a tibia, a humerus, some metatarsals, and the distal portion of a fragmentary pubic bones recovered from the

of Colorado. Research by Carpenter et al. (2005) concluded that these fossils are not ceratosaurian and are likely referable to the coelurid theropod ''

Tanycolagreus ''Tanycolagreus'' is a genus of coelurosaurian theropod from the Late Jurassic of North America. Discovery and naming In 1995 Western Paleontological Laboratories, Inc. uncovered the partial skeleton of a small theropod at the Bone Cabin Quarr ...

''. It is named after visual effects supervisor Phil Tippett. * ''Elaphrosaurus agilis'', was a renaming by Dale Russell in 1980 of '' Coelurus agilis'', originally named by Othniel Charles Marsh in 1884. 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 species ''Coelurus fragilis''. John Ostrom (1980) confirmed Charles Whitney Gilmore's earlier position that ''Coelurus agilis'' was synonymous with ''Coelurus fragilis''. This means that ''Elaphrosaurus agilis'' is actually the same animal as ''Coelurus fragilis'', its

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

. * ''Elaphrosaurus'' sp. USNM 8415, was discovered in 1883 and first referred to the ornithopod '' Dryosaurus''. It was later referred to ''Elaphrosaurus'' 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 to ''Elaphrosaurus''. Current knowledge limits the placement of this material to Ceratosauria incertae sedis.Carrano and Sampson, 2008. The phylogeny of Ceratosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology. 6, 183–236. * ''Elaphrosaurus'' sp. DMNH 36284, was referred to this genus by ChureChure, 2001. The second record of the African theropod Elaphrosaurus (Dinosauria, Ceratosauria) from the Western Hemisphere. Neues Jahrbuch für Geologie und Paläontologie – Monatshefte. 2001(9), 565–576. in 2001, based on the proximal portion of a fragmentary right tibia from the Brushy Basin Member of the Morrison Formation. Phylogenetic analysis by Carrano and Sampson (2008) showed that it was not basal ceratosaurian, but instead resembled the leg bone of an

abelisauroid Abelisauroidea is typically regarded as a Cretaceous group, though the earliest abelisauridae remains are known from the Middle Jurassic of Argentina (classified as the species Eoabelisaurus mefi) and possibly Madagascar (fragmentary remains o ...

theropod that has yet to be formally described.

Paleobiology

Paul (1988) noted that ''Elaphrosaurus bambergi'' was too small to prey on the sauropods and stegosaurs present in its paleoenvironment, and instead, it likely hunted the small and swift ornithopod herbivores. 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.

Paleoecology

Studies suggest that the

paleoenvironment Paleoecology (also spelled palaeoecology) is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescales. As a discipline, paleoecology interacts with, depends on and informs ...

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 ''Australodocus'' (meaning "southern beam" from the Latin ''australis'' "southern" and the Greek ''dokos''/δοκоς "beam") is a genus of sauropod dinosaur that lived during the Late Jurassic period, around 150 million years ago, in what is now ...

'', '' Janenschia'', '' Tornieria'' and '' Dicraeosaurus'', theropods similar to '' Allosaurus'' and '' Ceratosaurus'', the carcharodontosaurid ''

Veterupristisaurus ''Veterupristisaurus'' is an extinct genus of carcharodontosaurid theropod dinosaur known from the Jurassic of Tendaguru, Lindi Region of southeastern Tanzania. Discovery and naming ''Veterupristisaurus'' is known from the holotype specimen M ...

'', the stegosaurid '' Kentrosaurus'' and the iguanodontian '' Dysalotosaurus''. Dinosaurs shared this paleoenvironment with pterosaurs like '' Pterodactylus'' and '' Rhamphorhynchus'', as well as with early mammals.

References

Bibliography

* * Werner Janensch (1925) "Die Coelurosaurier und Theropoden der Tendaguru-Schichten Deutsch-Ostafrikas". (The coelurosaurs and theropods of the Tendaguru Formation, German East Africa). Full Text here
Janensch1925
{{Taxonbar, from=Q132550 Abelisaurs Kimmeridgian life Late Jurassic dinosaurs of Africa Fossils of Tanzania Tendaguru fauna Fossil taxa described in 1920 Taxa named by Werner Janensch