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Elaphrosaurus bambergi
Topic Started: Sep 29 2013, 05:44 AM (3,360 Views)
Carcharadon
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Elaphrosaurus bambergi

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Temporal range: Late Jurassic, 154-150Ma

Kingdom: Animalia
Phylum: Chordata
Clade: Sauropsida
Clade: Dinosauria
Clade: Theropoda
Clade: Averostra
Clade: †Ceratosauria
Genus: †Elaphrosaurus Janensch, 1920

Elaphrosaurus is a genus of ceratosaurian theropod dinosaur that lived approximately 154 to 150 million years ago during the later part of the Jurassic Period in what is now Tanzania in Africa. Elaphrosaurus was a medium-sized, but lightly-built, bipedal, carnivore, that could grow up to 6.2 m (20 ft) long. Morphologically, this dinosaur is significant in two ways. First, it has a relatively long trunk but is very shallow-chested for a theropod of its size. Second, its has very short hindlimbs when compared to its relatively long trunk. Phylogenetic analysis indicates that this genus is likely a ceratosaur, and earlier suggestions that it is a late surviving coelophysoid have been examined but generally dismissed.

Etymology
The genus name Elaphrosaurus is derived from the Greek words elaphro (ελαφρός) meaning "light" as in "light-weight", a reference to its slender frame and "sauros" (σαυρος) meaning "lizard"; thus, "lightweight lizard". Elaphrosaurus was described and named by Werner Janensch in 1920 and the type species is Elaphrosaurus bambergi.

Description
Elaphrosaurus was long and slender, with a long neck. It was distinctive among theropods for being short-legged for its length. Paul (1988) noted that this was the longest-trunked and shallowest-chested theropod that he has examined. Elaphrosaurus was about 6.2 m (20 ft) long, 1.46 m (5 ft) tall at the hip, and weighed about 210 kilograms (463 pounds). The tibia (shin bone) of Elaphrosaurus, measured 608 mm was considerably longer than its femur (thigh bone) that measured 520 mm, which indicates that it could probably run very fast. Its long tail ended with a rare downward bend which may be unrelated to taphonomy.
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Restoration of Elaphrosaurus bambergi with head and hands based on the related Limusaurus.

Classification
Elaphrosaurus was first described as a coelurid. At the time, Coeluridae was a wastebasket taxon for small theropods. Then, Elaphrosaurus was placed in the family Ornithomimidae because of its light frame and the fact that its humerus is straight and slender. Upon closer examination its limbs approximate those of Coelophysis. What is known about Elaphrosaurus mostly comes from a single nearly complete skeleton and no skull has been found. More recent work by Carrano and Sampson (2008) and Carrano et al. (2012) assign this genus to Ceratosauria. It is now believed that Limusaurus is its closest relative.

Nomina dubia (dubious names)
The following material was assigned to Elaphrosaurus over the years, but further study revealed that these assignments were dubious:

  • Elaphrosaurus iguidiensis, was described by Lapparent in 1960, and the material was collected in Algeria, Libya and Niger in Early Cretaceous sediments. The material consists of over 40 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 Lapparent in 1960, and the material was collected at the Tiouraren Formation in Niger in Middle-Late Jurassic sediments. This material, a complete neck vertebra, has since been renamed Spinostropheus gautieri by Sereno et al. (2004).
  • Elaphrosaurus philtippettensis, was erected by 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 Morrison Formation of Colorado. Further research by Carpenter et al. (2005) suggested that the fossils are not ceratosaurian and are likely referable to the coelurid theropod Tanycolagreus.
  • Elaphrosaurus agilis, was described Dale Russel in 1972, based on a pair of fused pubic bones that O.C. Marsh had earlier named Coelurus agilis, believing that this specimen represented a much larger version of the type specimen, Coelurus fragilis. John Ostrom (1980) confirmed Charles 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.
  • 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 bare any morphology that specifically ties it to Elaphrosaurus. Current knowledge limits the placement of this material to Ceratosauria incertae sedis.
  • Elaphrosaurus sp. DMNH 36284, was referred to this genus by Chure in 2001, based on the proximal portion of a fragmentary tibia also from the Morrison Formation. Phylogenetic analysis by Carrano and Sampson (2008) showed that was not ceratosaurian, but instead resembled the leg bone of an abelisauroid theropod that has yet to be formally described.


Distinguishing anatomical features
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 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


Paleoecology
Provenance and occurance
The type specimen of Elaphrosaurus bambergi HMN Gr.S. 38-44 was recovered in the Middle Dinosaur Member of the Tendaguru Formation 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 154 to 150 million years ago. This specimen is housed in the collection of the Humboldt Museum in Berlin, Germany.

A related animal, perhaps the same genus, was found in stratigraphic zones 2-4 of the Morrison Formation. Few theropod skeletons have been found, most discoveries being fragments.

Fauna and habitat
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. Dinosaurs shared this paleoenvironment with pterosaurs like Pterodactylus and Rhamphorhynchus, as well as with early mammals. 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.
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Edited by Taipan, Oct 8 2013, 09:13 PM.
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The theropod dinosaur Elaphrosaurus bambergi Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania
Oliver W. M. Rauhut,Matthew T. Carrano.

Journal reference:

Abstract

Theropod dinosaurs from the Late Jurassic of Gondwana are still poorly known, with Elaphrosaurus bambergi Janensch, 1920, from the late Kimmeridgian of Tendaguru, Tanzania, being the only taxon represented by more than isolated remains from Africa. Having long been considered a coelurosaurian, more specifically an ornithomimosaur, Elaphrosaurus is currently regarded as a basal ceratosaur. Here, we revise the osteology and phylogenetic position of this important taxon. Elaphrosaurus shows many unusual osteological characters, including extremely elongated and constricted cervical vertebrae, an expansive shoulder girdle with strongly modified forelimbs, a relatively small ilium, and elongate hindlimbs with a very small ascending process of the astragalus that is fused to the tibia. We found this taxon to share many derived characters with noasaurids, such as: strongly elongate cervical and dorsal vertebrae; low, rectangular neural spines in the mid-caudal vertebrae; presence of only an anterior centrodiapophyseal lamina in anterior caudal vertebrae; presence of a wide, U–shaped notch between the glenoid and the anteroventral hook in the coracoid; a laterally flared postacetabular blade of the ilium; a flat anterior side of the distal tibia; and a reduced shaft of metatarsal II. Our analysis placed Elaphrosaurus within a dichotomous Noasauridae as part of a Jurassic subclade, here termed Elaphrosaurinae, that otherwise includes taxa from eastern Asia. These results underscore the long and complex evolutionary history of abelisauroids, which is still only beginning to be understood.

Conclusions

Elaphrosaurus bambergi remains one of only two Late Jurassic Gondwanan theropods represented by adequate material to date (the second being therecently described Chilesaurus; Novas et al., 2015).Its skeletal morphology is highly derived in many respects, including strongly elongate cervical vertebrae, a short and robust forelimb, and elongate hindlimbs. The remains exhibit a suite of characters that allow its identification as abelisauroid, and within this clade, as a member of a newly recognized subclade, the Elaphrosaurinae. Elaphrosaurines obviously represented an early successful radiationof noasaurids, which is convergent in several respects to certain coelurosaur clades, both in anatomical and ecological specializations (Zanno &Makovicky, 2011). As far as their evolutionary history is known, they were restricted to the Jurassic,but achieved a possibly Pangea-wide distributionduring this time, as indicated by remains found infar disparate areas in Africa and eastern Asia. The recognition of this highly specialized radiation of abelisauroids underlines our still very poor knowledge of the evolutionary history of this clade.
Edited by Carnotaur, Oct 25 2016, 09:28 AM.
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Here is a description about the size and proportions of Elaphrosaurus,by Matthew T. Carrano and Oliver W. M. Rauhut:

Quote:
 
Given the incompleteness of the skeleton, the
length of Elaphrosaurus cannot be measured; how-
ever, reconstructing the missing elements of the ver-
tebral column, and assuming some 45 caudal
vertebrae, Janensch’s (1929) estimate of ~580 cm for
the total length of the vertebral column seems very
reasonable. As no elements of the skull are pre-
served, its length can only be guessed. In the basal
ceratosaur Ceratosaurus, the skull is approximately
as long as the femur (Gilmore, 1920), but in Limu-
saurus, probably a closer relative of Elaphrosaurus
(see below), the skull length is about half that of the
femur (Xu et al., 2009). Furthermore, the strongly
elongate cervical vertebrae with poorly developed
processes (neural spine and epipophyses) indicate
that the skull of Elaphrosaurus was light and thus
probably relatively small. Nevertheless, taking the
above values as limits for estimating skull size,the cranium
of this taxon was probably 25–50 cm long,
resulting in a total body length of 6.0–6.3 cm. This
body length is somewhat larger than that estimated
for the type specimens of Ceratosaurus (5.33–5.90 m)
and Dilophosaurus (5.07–6.05 m; Gilmore, 1920;
Welles, 1984; Paul, 1988; Therrien & Henderson,
2007). The femoral length of Elaphrosaurus
(529 mm) might seem to contradict this estimate, as
both Ceratosaurus and Dilophosaurus have longer
femora (620 and 557 mm, respectively; Gilmore,
1920; Welles, 1984), but this simply reflects different
limb proportions, as the entire hindlimb (measured
as femoral length +tibia length +length of metatar-
sus III) is longer in the former genus than in the lat-
ter taxa (1528 versus 1429, and 1412 mm,
respectively).

Also of interest is the body mass of Elaphrosaurus.
The only published estimates are those of Paul
(1988; 210 kg) and Christiansen & Fari~
na (2004;
245 kg), who used femur length and scaled volumet-
ric analysis, respectively. We estimated the body
mass of Elaphrosaurus on the basis of femoral cir-
cumference, using the formula of Campione et al.
(2014). The minimum circumference of 177 mm
occurs in the proximal part of the femur, just proxi-
mal to the cleft that separates the lesser trochanter
from the shaft, whereas the midshaft circumference
is 193 mm. These two measurements provide body
mass estimates of 322 and 409 kg, respectively. Com-
parisons with the body masses of the probably
slightly shorter Ceratosaurus (586 kg; USNM 4734)
and Dilophosaurus (330 kg; UCMP V.37302) underli-
nes the slender build of Elaphrosaurus.

The hindlimb proportions of Elaphrosaurus are
noteworthy. Most medium-sized theropods (4–7m
body length) tend towards limb proportions of an ‘in-
termediate’ nature, with proportionally short meta-
tarsals relative to the femur (Carrano, 1999). In
Elaphrosaurus, however, the metatarsals are 74% of
the femoral length. Among theropods with a body
mass of more than 100 kg, similar metatarsal pro-
portions are only found in some ornithomimosaurs
[e.g. metatarsal length is 77% of femoral length in
Struthiomimus altus (Lambe, 1902); Osborn, 1916].
Indeed, Elaphrosaurus exhibits some of the most
cursorial limb proportions known among dinosaurs;
in addition, the fourth trochanter is placed quite
proximally on the femoral shaft. Whether this indi-
cates especially rapid locomotion, or instead a wide-
ranging life habit, cannot yet be tested (Carrano,
1999).


Those are excerpts from the article above,which can be found here.

Summarizing,Elaphrosaurus probably was a medium sized(~6 meters long and 300kg-400kg heavy),and very elongated,ligthy build ceratosaurian theropod.Like the relative Limusaurus,it probably had a small skull,possibly a tooth-less beak.It had legs very well adapted for running,in spite of the elongate body proportions.


Curiously,this theropod shares some striking similarities with ornithomimosaurs(in fact,it was once believed that it was an ornithomimid).Maybe they had similar niche?




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Ausar
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Quote:
 
It had legs very well adapted for running,in spite of the elongate body proportions.
Eh, "in spite"?

cat loves food
Edited by Ausar, Jan 3 2017, 01:26 AM.
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Ausar
Jan 3 2017, 01:22 AM
Quote:
 
It had legs very well adapted for running,in spite of the elongate body proportions.
Eh, "in spite"?

cat loves food
Its because I would expect cursorial bipeds to have a compact body plan,in order to help decreasing the rotational inertia.
Edited by Carnotaur, Jan 3 2017, 02:13 AM.
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Ausar
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Carnotaur
Jan 3 2017, 01:40 AM
Ausar
Jan 3 2017, 01:22 AM
Quote:
 
It had legs very well adapted for running,in spite of the elongate body proportions.
Eh, "in spite"?

cat loves food
Its because I would expect cursorial bipeds to have a compact body plan,in order to help decreasing the rotational inertia.
That helps with agility, not speed, for one. Secondly, it's possible that an elongate body can also be more laterally flexible, which is another solution to reducing rotational inertia.
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Soopairik
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Great description! Nice job with the long article.
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