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Dacentrurus
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Dacentrurus
Dacentrurus (meaning "tail full of points") is an extinct genus of stegosaurian dinosaur from the Late Jurassic and perhaps Early Cretaceous (154–140 million years ago) of Europe. Its type species, D. armatus, was named in 1875 as Omosaurus armatus, based on a skeleton found in a clay pit in the Kimmeridge Clay in Swindon, England. In 1902 the genus was renamed Dacentrurus because the name Omosaurus had already been used for a phytosaur in 1856. After 1875, half a dozen other species would be named but perhaps only Dacentrurus armatus is valid.
Dacentrurus is among the largest known stegosaurs, measuring around 8–9 metres (26–30 ft) long and weighing up to 5–7.4 metric tons (5.5–8.2 short tons). Finds of this animal have been limited, so much of its appearance is uncertain and its relationship with other members of the Dacentrurinae are contentious. Some researchers suggest that Miragaia longicollum represents a junior synonym of this taxon.
On 23 May 1874, James Shopland of the Swindon Brick and Tyle Company reported in a letter to Professor Richard Owen that their clay pit, the Swindon Great Quarry below Old Swindon Hill at Swindon in Wiltshire, had again produced a fossil skeleton that he was willing to donate to the British Museum of Natural History. Owen sent out William Davies to secure the specimen, which proved to be encased in an eight feet high and six feet wide clay nodule. Owen presumed that the extremely hard nodule had been formed by vapours emitted by the decomposing carcass. During an attempt to lift it in its entirety, the loam clump crumbled into several pieces. These were eventually transported to London in crates with a total weight of three tonnes. The bones were subsequently partially uncovered by Owen's preparator, the mason Caleb Barlow.
Owen named and described the remains in 1875 as the type species Omosaurus armatus. The generic name is derived from Greek ὦμος, omos, "upper arm", in reference to the robust humerus. The specific name armatus can mean "armed" in Latin and in this case refers to a large spike that Owen assumed was present on the upper arm. The study was illustrated by high quality lithographs.
The holotype, NHMUK OR 46013, was found in a layer of the Kimmeridge Clay Formation dating from the late Kimmeridgian. The pits were soon abandoned; as a result it is no longer possible to determine their exact location and age. The holotype consists of a postcranial skeleton lacking the skull. The main nodule fragment contains the pelvis; a series of six posterior dorsal vertebrae, all sacrals and eight anterior caudal vertebrae; a right femur and some loose vertebrae. In all, thirteen detached vertebrae are present in the material. Also an almost complete left forelimb was contained by another loam clump. Additional elements include a partial right fibula with calcaneum, a partial tibia, a right neck plate and a left tail spike.
Several other species would be named within the genus Omosaurus. Part of the British Museum of Natural History collection was specimen NHMUK 46320, a pair of spike bases found in the Kimmeridge Clay by William Cunnington near the Great Western Railway cutting near Wootton Bassett. These Owen in 1877 named Omosaurus hastiger, the epithet meaning "spike-bearer" or "lance-wielder", the spikes by him seen as placed on the wrist of the animal.
In 1887, John Whitaker Hulke named Omosaurus durobrivensis based on specimen NHMUK R1989 found at Tanholt, close to Eye, Cambridgeshire, the specific name being derived from Durobrivae. (That specimen is sometimes mistakenly said to have been found at Fletton, Peterborough, Cambridgeshire, which is where Alfred Nicholson Leeds made most of his finds.) This in 1956 became the separate genus Lexovisaurus.
In 1893, Harry Govier Seeley named Omosaurus phillipsii, based on a left femur of a young individual found at Slingsby, North Yorkshire, specimen YM 498, the epithet honouring the late John Phillips. Seeley suggested this may be the same taxon as Priodontognathus phillipsii Seeley 1869, which has led to the misunderstanding, due to its having the same specific name, that Priodontognathus was simply subsumed by him under Omosaurus. This interpretation however, is incorrect as both species have different holotypes. O. phillipsii has been considered a nomen dubium. "Omosaurus leedsi" is a nomen nudum used by Seeley on a label for CAMSM J.46874, a plate found in Cambridgeshire, the epithet honouring Alfred Nicholson Leeds.
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Dacentrurus
Dacentrurus (meaning "tail full of points") is an extinct genus of stegosaurian dinosaur from the Late Jurassic and perhaps Early Cretaceous (154–140 million years ago) of Europe. Its type species, D. armatus, was named in 1875 as Omosaurus armatus, based on a skeleton found in a clay pit in the Kimmeridge Clay in Swindon, England. In 1902 the genus was renamed Dacentrurus because the name Omosaurus had already been used for a phytosaur in 1856. After 1875, half a dozen other species would be named but perhaps only Dacentrurus armatus is valid.
Dacentrurus is among the largest known stegosaurs, measuring around 8–9 metres (26–30 ft) long and weighing up to 5–7.4 metric tons (5.5–8.2 short tons). Finds of this animal have been limited, so much of its appearance is uncertain and its relationship with other members of the Dacentrurinae are contentious. Some researchers suggest that Miragaia longicollum represents a junior synonym of this taxon.
On 23 May 1874, James Shopland of the Swindon Brick and Tyle Company reported in a letter to Professor Richard Owen that their clay pit, the Swindon Great Quarry below Old Swindon Hill at Swindon in Wiltshire, had again produced a fossil skeleton that he was willing to donate to the British Museum of Natural History. Owen sent out William Davies to secure the specimen, which proved to be encased in an eight feet high and six feet wide clay nodule. Owen presumed that the extremely hard nodule had been formed by vapours emitted by the decomposing carcass. During an attempt to lift it in its entirety, the loam clump crumbled into several pieces. These were eventually transported to London in crates with a total weight of three tonnes. The bones were subsequently partially uncovered by Owen's preparator, the mason Caleb Barlow.
Owen named and described the remains in 1875 as the type species Omosaurus armatus. The generic name is derived from Greek ὦμος, omos, "upper arm", in reference to the robust humerus. The specific name armatus can mean "armed" in Latin and in this case refers to a large spike that Owen assumed was present on the upper arm. The study was illustrated by high quality lithographs.
The holotype, NHMUK OR 46013, was found in a layer of the Kimmeridge Clay Formation dating from the late Kimmeridgian. The pits were soon abandoned; as a result it is no longer possible to determine their exact location and age. The holotype consists of a postcranial skeleton lacking the skull. The main nodule fragment contains the pelvis; a series of six posterior dorsal vertebrae, all sacrals and eight anterior caudal vertebrae; a right femur and some loose vertebrae. In all, thirteen detached vertebrae are present in the material. Also an almost complete left forelimb was contained by another loam clump. Additional elements include a partial right fibula with calcaneum, a partial tibia, a right neck plate and a left tail spike.
Several other species would be named within the genus Omosaurus. Part of the British Museum of Natural History collection was specimen NHMUK 46320, a pair of spike bases found in the Kimmeridge Clay by William Cunnington near the Great Western Railway cutting near Wootton Bassett. These Owen in 1877 named Omosaurus hastiger, the epithet meaning "spike-bearer" or "lance-wielder", the spikes by him seen as placed on the wrist of the animal.
In 1887, John Whitaker Hulke named Omosaurus durobrivensis based on specimen NHMUK R1989 found at Tanholt, close to Eye, Cambridgeshire, the specific name being derived from Durobrivae. (That specimen is sometimes mistakenly said to have been found at Fletton, Peterborough, Cambridgeshire, which is where Alfred Nicholson Leeds made most of his finds.) This in 1956 became the separate genus Lexovisaurus.
In 1893, Harry Govier Seeley named Omosaurus phillipsii, based on a left femur of a young individual found at Slingsby, North Yorkshire, specimen YM 498, the epithet honouring the late John Phillips. Seeley suggested this may be the same taxon as Priodontognathus phillipsii Seeley 1869, which has led to the misunderstanding, due to its having the same specific name, that Priodontognathus was simply subsumed by him under Omosaurus. This interpretation however, is incorrect as both species have different holotypes. O. phillipsii has been considered a nomen dubium. "Omosaurus leedsi" is a nomen nudum used by Seeley on a label for CAMSM J.46874, a plate found in Cambridgeshire, the epithet honouring Alfred Nicholson Leeds.
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