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''Eustreptospondylus'' ( ;), from 
Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
εὖ (''eû''), meaning "well", στρεπτός (''streptós''), meaning "twisted", and σπόνδυλος (''spóndulos''), meaning "vertebra", is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of megalosaurid
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
, from the
Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 165.3 ± 1.1 Ma (million years ago) and 161.5 ± 1.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...
and Kimmeridgian stages 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 (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
period (some time between 166 and 154 million years ago) in southern
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
, at a time when
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
was a series of scattered islands (due to tectonic movement at the time which raised the sea-bed and flooded the lowland).


Discovery and naming

In 1870, workers at the Summertown Brick Pit, just north of
Oxford Oxford () is a City status in the United Kingdom, cathedral city and non-metropolitan district in Oxfordshire, England, of which it is the county town. The city is home to the University of Oxford, the List of oldest universities in continuou ...
, England, found the skeleton of a theropod. The remains were acquired by the local bookseller James Parker, who brought them to the attention of Oxford Professor John Phillips. Phillips described the bones in 1871, but did not name them. At the time, the remains represented the most complete skeleton of a large theropod ever found. ''Eustreptospondylus'' is still the most complete of any large Jurassic European theropod. In 1890, the skeleton was bought by
Oxford University The University of Oxford is a collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the second-oldest continuously operating u ...
, and Arthur Smith Woodward examined it and referred it to ''
Megalosaurus ''Megalosaurus'' (meaning "great lizard", from Ancient Greek, Greek , ', meaning 'big', 'tall' or 'great' and , ', meaning 'lizard') is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic Epoch (Bathonian stage, 166 ...
bucklandii''. In 1905 and 1906 Baron Franz Nopcsa reassigned the skeleton to the species, ''Streptospondylus cuvieri'', which had been first described by Sir
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...
in 1842, based on a now lost vertebra from the
Bathonian In the geologic timescale the Bathonian is an age (geology), age and stage (stratigraphy), stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 annum, Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds ...
stage of the Jurassic period. The reason for this assignment was that the type species ''Streptospondylus altdorfensis'' from France, was a clearly related form, and Nopcsa decided to subsume all British material of this nature under a single ''Streptospondylus'' species, for which then the name ''S. cuvieri'' could not be avoided. The assignment of a rather complete find to a species based on very poor remains was troublesome. This was compounded by German palaeontologist Friedrich von Huene, who sometime referred to the specimen as ''Streptospondylus cuvieri'' and at other times considered it a species of ''Megalosaurus'': '' Megalosaurus cuvieri''. In 1964, Alick Donald Walker clarified matters by erecting a separate genus and species for the Oxford specimen: ''Eustreptospondylus oxoniensis''. The genus name ''Eustreptospondylus'', was intended to mean "true ''Streptospondylus''". ''Streptospondylus'' means "turned vertebra", and is derived from the
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
words ''streptos'' (στρεπτος) meaning "reversed" and ''spondylus'' (σπονδυλος), a reference to the fact that its dorsal vertebrae were opisthocoelous, in contrast to the typical procoelous vertebrae of crocodiles. The specific name "oxoniensis", refers to its provenance from Oxford. The
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
, OUM J13558, was recovered by W. Parker from claystone in a marine layer of the Stewartby Member of the Oxford Clay Formation, which dates to the Callovian stage of the Jurassic period, approximately 162 million years ago. It consists of a rather complete skeleton, with a skull which is missing elements including the nasal bones, the jugals, the rear ends of the lower jaws, the lower arms and the end of the tail. It represents a subadult individual. The only other specimen ever referred to ''Eustreptospondylus oxoniensis'' is OUMNH J.29775, a left ilium. The holotype was fully prepared and exhibited in 1924, in a rather erect position. In the early twenty-first century a new display changed this to a horizontal position of the body. In 2000, Oliver Walter Mischa Rauhut found that only minor differences in the hip bones — a more upward extending fusion of the "feet" of the
pubic bone In vertebrates, the pubis or pubic bone () forms the lower and anterior part of each side of the hip bone. The pubis is the most forward-facing (ventral and anterior) of the three bones that make up the hip bone. The left and right pubic bones ar ...
s — make ''Eustreptospondylus'' different from a previously known megalosaurid called '' Magnosaurus'', and in 2003 he proposed that they should be the same genus, which would make the full species name ''Magnosaurus oxoniensis''. In 2010,
Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology. He is best known for his work and research on theropoda, theropod dinosaurs and his detailed illustrations, both l ...
considered the species identical to ''Streptospondylus altdorfensis''.Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 89 The first detailed description of the ''Eustreptospondylus'' material was in 1906 by Nopcsa. A modern description was published in 2008 by Rudyard Sadleir e.a.R. Sadleir, P.M. Barrett and H.P. Powell, 2008, ''The anatomy and systematics of ''Eustreptospondylus oxoniensis'', a theropod dinosaur from the Middle Jurassic of Oxfordshire, England'', Monograph of the Palaeontological Society, 160(627) 82 pp In 1964, Walker also named a second species of ''Eustreptospondylus'': ''Eustreptospondylus divesensis'', based on a French find. In 1977 this became the separate genus '' Piveteausaurus''.


Description

The main specimen of ''Eustreptospondylus'' was not fully grown, and according to an estimate by Paul in 1988 was about long and weighed about . Various estimates suggest that ''Eustreptospondylus'' was an "average-sized" theropod, with a hypothetical adult length of around , and a mass of . The skull of ''Eustreptospondylus'' has a rather pointed snout in side view, with a large horizontally oriented nostril. There is no lacrimal horn. The skull roof is relatively thick. Oblique grooves in the jaw joints caused the gape of the mouth to be widened when the lower jaws were opened. These jaws at the front are rather tall and wide. No teeth have been preserved in either the upper or lower jaws, but the size of its toothsockets proves that the third tooth of the lower jaw was enlarged. Though not keeled, the front dorsal vertebrae have paired hypapophyses at their undersides, just as with ''Streptospondylus altdorfensis''.


Distinguishing anatomical features

Sadleir et al. (2008) established several traits that distinguish ''Eustreptospondylus'' from its direct relatives. In the corner of the lacrimal a shallow depression is present, which is pierced by a smaller foramen. The descending branch of the postorbital has a groove in its outer rear corner. The outer side of the
squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestra ...
has a well-developed drooping flange covering, in side view, the upper rear part of the lateral temporal
fenestra A fenestra (fenestration; : fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biology, biological sciences. It is the Latin word for "window", and is used in various fields to describe a pore in an anatomy, ...
. The tenth neck vertebra has a clear depression on its front underside. The neck and dorsal vertebrae are not keeled. In 2012 Matthew Carrano added to these traits. The peduncle of the ilium to which the
pubic bone In vertebrates, the pubis or pubic bone () forms the lower and anterior part of each side of the hip bone. The pubis is the most forward-facing (ventral and anterior) of the three bones that make up the hip bone. The left and right pubic bones ar ...
is attached, is as transversely wide as it is long from front to rear. With the rear blade of the ilium, the lower edge of the outer blade side is turned upwards to an almost horizontal position, creating and denuding over its total length a bone surface, the "brevis shelf", forming the internal face of the inner blade side — this shelf with dinosaurs functions as an attachment area for a tail muscle, the ''Musculus caudofemoralis brevis''.M.T. Carrano, R.B.J. Benson, and S.D. Sampson, 2012, "The phylogeny of Tetanurae (Dinosauria: Theropoda)", ''Journal of Systematic Palaeontology'' 10(2): 211-300 Sadleir also found additional traits proving that ''Eustreptospondylus'' differed from ''Magnosaurus nethercombensis'' in more than a single detail. The interdental plates reinforcing the back of the teeth are longer from front to rear than they are tall; with ''M. nethercombensis'' the opposite is true. Seen from above, the pubic bone forms transversely a more narrow part of the lower rim of the hip joint. Seen from behind, the upper part of the inner side of the thighbone is straight. The cnemial crest of the upper shinbone has no ridge running to the front and below, on its outer side.


Classification

In 1964, Walker assigned ''Eustreptrospondylus'' to the
Megalosauridae Megalosauridae is a monophyletic Family (taxonomy), family of Carnivore, carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dino ...
, which was historically included in a paraphyletic " Carnosauria", though sometimes a separate Eustreptospondylidae was recognised.S.M. Kurzanov, 1989, "O proiskhozhdenii i evolyutsii infraotryada dinozavrov Carnosauria", ''Paleontologicheskiy Zhurnal'' 1989(4): 3-14 Today ''Eustreptospondylus'' is commonly considered a member of the Eustreptospondylinae, clade within the Megalosauridae. A possible position of ''Eustreptospondylus'' in the evolutionary tree is given by this cladogram based on a
cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
analysis by Carrano ''et.al.'':


Paleobiology


Diet

''Eustreptospondylus'', like many other theropods, fed on smaller dinosaurs and pterosaurs, or scavenged the carcasses of fishes, marine reptiles, and other dinosaurs. It might have foraged on shorelines for carcasses and marine life.


Swimming

''Eustreptospondylus'' is known from a fossil from what was an island, at a time when Europe consisted mostly of archipelagos. This suggests that it might have been able to swim short distances. ''Eustreptospondylus'' has been considered a good swimmer, strong enough to swim from island to island like the modern day
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a large reptile of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo (island), Komodo, Rinca, Flores, Gili Dasami, and Gili ...
. Not all palaeontologists agree with the swimming hypothesis. The opposing theories hold that the fossil of ''Eustreptospondylus'' was either swept out to sea during a flood after the animal died on the mainland, or it was carried to the ocean after it died in a river.


Insular dwarfism

''Eustreptospondylus'' has been portrayed as a genus that evolved
insular dwarfism Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is disti ...
. In 2000, David Martill and Darren Naish pointed out that the portrayal of the animal as an island-dwelling dwarf species was caused by not realizing that the holotype specimen represented a subadult.


References

{{Taxonbar, from=Q131213 Megalosauridae Dinosaur genera Oxfordian dinosaurs Oxford Clay Fossil taxa described in 1964 Taxa named by Alick Walker Dinosaurs of the United Kingdom