''Sarcosaurus'' (meaning "flesh lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of basal

neotheropod Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and is the only group of theropods that survived the Triassic–Jurassic extinction event. All neotheropods became extinct by the e ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

, 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 In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...

stages of the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

, about 199-194 million years ago. ''Sarcosaurus'' is one of the earliest known

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 (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

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 femoral head (femur head or head of the femur) is the highest part of the thigh bone (femur). It is supported by the femoral neck. Structure The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a l ...

. 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 The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

; WARMS G667–690, a partial skeleton of a single individual that includes posterior dorsal vertebra, middle

caudal vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

, 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 The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with t ...

and tibiae, proximal end of left

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

, probable distal half of fibula, distal portions of

metatarsals The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medi ...

IV, II or III proximal half of left pedal

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particularly use ...

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 ''Dilophosaurus'' ( ) is a genus of theropod dinosaurs that lived in what is now North America during the Early Jurassic, about 193 million years ago. Three skeletons were discovered in northern Arizona in 1940, and the two best preserved ...

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

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s 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, ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

, ''Sarcosaurus woodi'', was first described by

Charles William Andrews Charles William Andrews (30 October 1866 – 25 May 1924) F.R.S., was a British palaeontologist whose career as a vertebrate paleontologist, both as a curator and in the field, was spent in the services of the British Museum, Department of Ge ...

in 1921 shortly after a partial skeleton had been found by S.L. Wood near

Barrow-on-Soar Barrow upon Soar is a large village in northern Leicestershire, in the Soar Valley between Leicester and Loughborough, with a population at the 2011 census of 5,856. Geography Barrow lies on the east bank of the River Soar, where the riv ...

, in the

Scunthorpe Mudstone The Scunthorpe Mudstone is a geologic formation in England. It preserves plesiosaur fossils dating back to the Late Triassic (Rhaetian) to Early Jurassic (Hettangian) period. It predominantly consists of grey mudstone with thin beds of argillaceo ...

. The generic name is derived from Greek ''sarx'', "flesh". The specific name honours Wood. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, 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 The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

and the upper part of a

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

. 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

, BMNH R3542, described by

Arthur Smith Woodward Sir Arthur Smith Woodward, FRS (23 May 1864 – 2 September 1944) was an English palaeontologist, known as a world expert in fossil fish. He also described the Piltdown Man fossils, which were later determined to be fraudulent. He is not relate ...

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 ''Magnosaurus'' (meaning 'large lizard') was a genus of theropod dinosaur from the Middle Jurassic of England. It is based on fragmentary remains and has often been confused with or included in ''Megalosaurus''. History and taxonomy In 1923, Fr ...

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 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 ...

. In 1974 ''S. andrewsi'' was reclassified as ''

Megalosaurus ''Megalosaurus'' (meaning "great lizard", from Greek , ', meaning 'big', 'tall' or 'great' and , ', meaning 'lizard') is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic period (Bathonian stage, 166 million years a ...

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 In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

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 A trochanter is a tubercle of the femur near its joint with the hip bone. In humans and most mammals, the trochanters serve as important muscle attachment sites. Humans are known to have three trochanters, though the anatomic "normal" includes ...

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 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 relatively ...

. The first to suggest a more basal position was

Samuel Paul Welles Samuel Paul Welles (November 9, 1907 – August 6, 1997) was an American palaeontologist. Welles was a research associate at the Museum of Palaeontology, University of California, Berkeley. He took part in excavations at the Placerias Quarry in ...

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 Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earliest ...

, 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 ''Saltriovenator'' (meaning "Saltrio hunter") is a genus of ceratosaurian dinosaur that lived during the Sinemurian stage of the Early Jurassic in what is now Italy. The type and only species is ''Saltriovenator zanellai''; in the past, the sp ...

'' 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 Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs, namely Ceratosauria and Tetanurae, and represent the only group of post-Early Jurassic theropods. Both survived into the Cretaceous period. When the Cretaceous–Paleo ...

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 Warwickshire (; abbreviated Warks) is a county in the West Midlands region of England. The county town is Warwick, and the largest town is Nuneaton. The county is famous for being the birthplace of William Shakespeare at Stratford-upon-Avon an ...

, is represented by the upper part of the Rugby Limestone Member (Hettangian-Sinemurian) of the Blue Lias Formation. 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. The western margin of the emergent London Platform 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