| Metriacanthosaurus | |
|---|---|
 | |
| Part of theholotype ofMetriacanthosaurus parkeri (individual fossils not to scale) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Metriacanthosauridae |
| Subfamily: | †Metriacanthosaurinae |
| Genus: | †Metriacanthosaurus Walker, 1964 |
| Type species | |
| †Metriacanthosaurus parkeri von Huene, 1923 | |
| Synonyms | |
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Metriacanthosaurus (meaning "moderately-spined lizard") is agenus ofmetriacanthosauriddinosaur from theOxford Clay Formation ofEngland, dating to theLate Jurassicperiod, about 160 million years ago (lowerOxfordian). It is the only metriacanthosaurid currently named from outside of Asia.
The holotype ofMetriacanthosaurus parkeri, specimenOUM J.12144, was discovered in 1871 by W. Parker atJordan's Cliff, nearWeymouth,Dorset, on the southwest coast of England.[1] The specimen includes an incomplete hip, a leg bone, and part of a backbone; thegeologistJohn Phillips briefly commented on the specimen during the same year.[2] These bones were from theOxford Clay Formation, which dates to theUpper Jurassic.[3]
In 1923, German paleontologistFriedrich von Huene wrote a paper onJurassic andCretaceous European carnivorous dinosaurs withinSaurischia. In this paper, he examined OUM J.12144, assigning it to a new species ofMegalosaurus:Megalosaurus parkeri.[1] Thespecific name honours W. Parker. In 1932, however, von Huene concluded it was a species ofAltispinax,A. parkeri.[4]
In 1964, scientistAlick Walker decided these fossils were too different fromAltispinax, as they lacked the long vertebral spines, and named the new genusMetriacanthosaurus.[5] The generic name is derived from Greekmetrikos, "moderate", andakantha, "spine".Metriacanthosaurus thus gets its name from itsvertebrae, which are taller than typical carnosaurs, likeAllosaurus, but lower than other high-spined dinosaurs likeAcrocanthosaurus.
Metriacanthosaurus was a medium-sized theropod with a femur length of 80 cm (31 in).Gregory S. Paul in 1988 estimated its weight at 1 tonne (1.1 short tons).[6] Thomas Holtz gave a length of 8 meters (26.2 feet).[7]Metriacanthosaurus was named for the height of itsneural spines, which are actually not overly tall for theropods.[3] They are similar to other theropods such asMegalosaurus,Sinraptor, andCeratosaurus in being 1.5 times the height of thecentrum.[8]
Originally named as a species ofMegalosaurus inMegalosauridae,Metriacanthosaurus has since been reclassified inMetriacanthosauridae. It is thought to be related to genera such asYangchuanosaurus, and in 1988 Paul synonymized the two genera. However, a 2007 review of British dinosaurs byDarren Naish andDavid Martill defending keeping the two genera taxonomically separate.[3]Metriacanthosaurus is considered a member of the subfamilyMetriacanthosaurinae.[9]
Below is a simplified cladogram ofTetanurae byMatthew Carranoet al. (2012).[9]
Metriacanthosaurus is the only known member of Metriacanthosauridae outside of Asia (other than possible fragmentary records from the geographically closeFalaises des Vaches Noires locality of northern France, which is probably similar in age toMetriacanthosaurus[10]). The earliest records of metriacanthosaurids in Asia are from the early Middle Jurassic, withMetriocanthosaurus being nested within the diversity of Asian metriacanthosaurids.Metriacanthosaurus thus likely represents a dispersal event from Asia into Europe during the early Late Jurassic.Metriacanthosaurus appears to have lived alongside other large theropods belonging to the familyMegalosauridae.[11] Other dinosaurs known from the Oxford Clay (which both spans the precedingCallovian and the Oxfordian) include the megalosaurid theropodEustreptospondylus, the sauropodCetiosauriscus, the stegosaursLexovisaurus andLoricatosaurus, the ankylosaurSarcolestes, and the iguanodontianCallovosaurus.,[12] with the poorly known ankylosaurCryptosaurus also being known from Oxfordian aged sediments in Britain.[13][14] During this time, Europe formed anarchipelago of islands surrounded by shallow seas, explaining the findings of these dinosaurs in marine sediments.[10]
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