''Sarcosaurus'' (meaning "flesh lizard") is a genus of basal neotheropod dinosaur, roughly long. It lived in what is now England during the

Hettangian The Hettangian is the earliest age and lowest stage of the Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (My ...

- Sinemurian stages of the Early Jurassic, about 199-194 million years ago. ''Sarcosaurus'' is one of the earliest known Jurassic theropods, and one of only a handful of theropod genera from this time period. Along with '' Dracoraptor hanigani'' it is one of the two described neotheropods from the lowermost Jurassic of the United Kingdom.

Description

The holotype is NHMUK PV R4840 a partial skeleton that includes a posterior

dorsal vertebra In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

, partial left and right ilia, that are fused to the proximal portion of the pubis, lacking the femoral head. The specimen shows some evidence of skeletal maturity, meaning it is not an early juvenile, but its exact ontogenetic stage cannot be ascertained. Referred specimens include the non mature NHMUK PV R3542 (holotype of ''Sarcosaurus andrewsi'') that includes a complete right tibia; WARMS G667–690, a partial skeleton of a single individual that includes posterior dorsal vertebra, middle caudal vertebra, dorsal

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

fragments, left ilium, right and left pubes, femora and tibiae, proximal end of left fibula, probable distal half of fibula, distal portions of metatarsals IV, II or III proximal half of left pedal phalanx II-1, and three indeterminate bone fragments.Carrano and Sampson (2004). "A review of coelophysoids (Dinosauria: Theropoda) from the Early Jurassic of Europe, with comments on the late history of the Coelophysoidea." ''N. Jb. Geol. Palaont. Mh.'', 2004(9): 537-558. ''Sarcosaurus'' shares certain morphological conditions with other neotheropods, including ''

Liliensternus ''Liliensternus'' is an extinct genus of basal neotheropod dinosaur that lived approximately 210 million years ago during the latter part of the Triassic Period in what is now Germany. ''Liliensternus'' was a moderate-sized, bipedal, ground-dwel ...

liliensterni'' (collateral fossae of the metatarsal II with similar development and shape on both sides, larger ratio on the centrum) and '' Dilophosaurus wetherilli'' (lateral collateral fossa is bigger than the medial one in the metatarsal, middle caudal series proportionately lower and narrower than the middle−posterior dorsal vertebra). ''Sarcosaurus'' was a bipedal predator, probably able to run fast and catch small prey. The holotype belonged to a 3.5 m long animal whose weight was no greater than 50–60 kg. NHMUK PV R3542 belonged to a larger animal, estimated to have had a maximum length of 5 m and a weight of 140 kg.

History of discovery

The fossils of ''Sarcosaurus'' were found in the

Lower Lias The Lias Group or Lias is a lithostratigraphic unit (a sequence of rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, ...

of England. The type species, ''Sarcosaurus woodi'', was first described by Charles William Andrews in 1921 shortly after a partial skeleton had been found by S.L. Wood near Barrow-on-Soar, in the Scunthorpe Mudstone. The generic name is derived from Greek ''sarx'', "flesh". 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 Wood. The holotype, BMNH 4840/1, consists of a

pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

, a vertebra and the upper part of a femur. The preserved length of the femur is . A second species, ''Sarcosaurus andrewsi'', was named by

Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...

in 1932, based on a tibia, BMNH R3542, described by Arthur Smith Woodward in 1908 and found near

Wilmcote Wilmcote is a village, and since 2004 a separate civil parish, in the English county of Warwickshire, about north of Stratford-upon-Avon. Prior to 2004, it was part of the same parish as Aston Cantlow, and the 2001 population for the whole are ...

. Confusingly von Huene in the same publication named the very same fossil '' Magnosaurus woodwardi''. Later he made a choice for ''S. andrewsi'' to be the valid name. Huene also discussed WARMS G667–690, a partial skeleton also from Wilmcote, both specimens are from the Blue Lias. In 1974 ''S. andrewsi'' was reclassified as '' Megalosaurus andrewsi'' by

Michael Waldman Michael A. Waldman is an American attorney and presidential speechwriter and political advisor, currently serving as the president of the Brennan Center for Justice, Brennan Center for Justice at NYU School of Law, a nonprofit law and policy inst ...

, on the probably erroneous assumption it was a

megalosaurid Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs. They were a relative ...

. A later study concluded the two species to be indistinguishable except for size, but other authors consider any identity to be unprovable as there are no comparable remains and conclude both species to lack autapomorphies and therefore to be ''

nomina dubia In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

''. Von Huene in 1932 referred a partial skeleton from the collection of the Warwick Museum to ''S. woodi'' but the identity was unproven; in 1995 it was given the informal name "Liassaurus" but this has remained a ''

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate descr ...

''. The specimen is likely one individual, located in the same stratiagraphic position as the holotypic specimen. Unfortunately, there are few available overlapping elements from the specimen and the holotype. Both specimens preserve a relatively complete femur: however, the features of both (an anteromedially directed head, a relatively long fourth trochanter and a trochanteric shelf) are plesiomorphic and thus do not indicate conspecifity or clade membership. It is noted, however, that there are no features which are present in one specimen but not the other. In 2020 WARMS G667–690 was given a comprehensive redescription, which proposed that all three specimens belonged to the same species, ''Sarcosaurus woodi''.

Phylogeny

Andrews originally assigned ''Sarcosaurus'' to the Megalosauridae. The first to suggest a more basal position was Samuel Paul Welles who placed it in the

Coelophysidae Coelophysidae is a family of primitive carnivorous theropod dinosaurs. Most species were relatively small in size. The family flourished in the Late Triassic and Early Jurassic periods, and has been found on numerous continents. Many members of C ...

. Later analyses resulted in either a position in the Ceratosauria, or in the

Coelophysoidea Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the ...

. Ezcurra (2012) found ''Sarcosaurus'' to be the most basal ceratosaur in a large unpublished analysis. In 2018, Andrea Cau in the large analysis of '' Saltriovenator'' found ''Sarcosaurus'' to be a dilophosaurid with good amount of support in the data.Dal Sasso C, Maganuco S, Cau A. 2018
The oldest ceratosaurian (Dinosauria: Theropoda), from the Lower Jurassic of Italy, sheds light on the evolution of the three-fingered hand of birds.
PeerJ 6:e5976 In 2020, Ezcurra ''et al.'' recovered ''Sarcosaurus'' as a close relative of Averostra due to the presence of shared characters including an anteroventrally oriented ventral margin of the preacetabular process in lateral view on the ilium and a femur with a poorly posteriorly developed fourth trochanter. Their cladogram is shown below:

Palaeoenvironment

Holotype specimen was collected from strata (bucklandi zone, Sinemurian) that were deposited in epicontinental, shallow, marine settings affected by sea-level fluctuations and a warm, predominantly humid climate. In south-western Warwickshire, is represented by the upper part of the Rugby Limestone Member (Hettangian-Sinemurian) of the

Blue Lias Formation The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassi ...

. with typical lithofacies of alternating mudrocks and generally fine-grained and frequently highly fossiliferous limestones. the Rugby Limestone Member was deposited at a palaeolatitude of approximately 35° N in a storm-influenced offshore setting.

was related to the eastern margin of the Worcester Graben during the Early Jurassic and adjacent to the

East Midlands Shelf East or Orient is one of the four cardinal directions or points of the compass. It is the opposite direction from west and is the direction from which the Sun rises on the Earth. Etymology As in other languages, the word is formed from the fac ...

. The western margin of the emergent

London Platform The London Basin is an elongated, roughly triangular sedimentary basin approximately long which underlies London and a large area of south east England, south eastern East Anglia and the adjacent North Sea. The basin formed as a result of thrust ...

at 60−80 km to the south-east was probably the principal source of terrestrial biodebris.Cox BM, SumblerMG, Ivimey-Cook HC. 1999. "A formational framework for the Lower Jurassic of England and Wales (onshore area)". British Geological Survey Research Report RR/99/01: 1–28.

References

External links