Xenoposeidon
Encyclopedia
Xenoposeidon is a genus
of sauropod dinosaur
from the Early Cretaceous
of England
, living about 140 million years ago. It is known from a single partial vertebra with unusual features, unlike those of other sauropods. This bone was first discovered in the early 1890s but received little attention until it was found by University of Portsmouth
student Mike Taylor
, who formally described and named it in 2007 with Darren Naish
.
BMNH
R2095, a partial posterior
back vertebra. The specimen lacks the anterior face of the centrum
and the upper portion of the neural arch
. The centrum is estimated at 200 millimetres (7.9 in) long, and the height of the preserved portion of the vertebra is 300 millimetres (11.8 in). The average diameter of the posterior face of the centrum is 165 millimetres (6.50 in), with a concave surface. This concavity is deep enough to suggest that the anterior faces of vertebrae from this part of the dinosaur's spine would have been convex to articulate with such a shape.
The specimen displays several distinguishing characteristics. The base of the neural arch covers the length of the centrum and is continuous with the centrum's posterior face. The neural arch leans anteriorly at 35° and there are broad areas of featureless bone on the lateral surfaces of the arch. The neural canal
is large and teardrop-shaped anteriorly but small and circular at its posterior opening. The various bony struts and sheets that make up the arch have a distinctive configuration.
analysis
, they found that, although a neosauropod
, it didn’t fit ‘comfortably’ into any of the established groups, Diplodocoidea
, Camarasauridae, Brachiosauridae
and Titanosauria. Xenoposeidon could be a derived
member of one of the known groups, or may even represent a new group. The authors left it as a neosauropod of uncertain affinities
.
in East Sussex
, England, in rocks of the Hastings Bed Group. This formation
dates to the Lower Cretaceous, and is within the Berriasian
and Valanginian
Stages
. The vertebra was probably from the Berriasian portion of the Ashdown Beds Formation within the Hastings, although precise information about the locality and stratigraphy have been lost if such data were ever recorded.
The partial posterior
back vertebra, cataloged as BMNH R2095, was briefly described by English naturalist
and paleontologist Richard Lydekker
in 1893. He thought that it might belong to Cetiosaurus
brevis, better known today as Pelorosaurus conybearei
. The bone attracted little attention for decades, sitting on a shelf at the British Natural History Museum
in London
for 113 years. Mike Taylor, a sauropod vertebra specialist, stumbled upon it and became interested in the unusual specimen, entering into a description of it with Darren Naish.
The new genus was first announced by the British Palaeontological Association on November 15, 2007. The genus consists of the single species Xenoposeidon proneneukos. The species name means ‘forward sloping’, in recognition of the anterior sloping of the neural arch
. This unusual characteristic, along with its other distinctive features, prompted the authors to erect the new genus.
al herbivore
. It was relatively small for a sauropod. Extrapolating from the vertebra suggests that the type
individual of Xenoposeidon could have been about 15 metres (50 ft) long and weighed approximately 7.6 tonne
s (8.4 short ton
s), if it resembled Brachiosaurus
, to 20 m (65 ft) long and 2.8 tonnes (3.1 short tons), if it was built like the longer, lighter Diplodocus
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of sauropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, living about 140 million years ago. It is known from a single partial vertebra with unusual features, unlike those of other sauropods. This bone was first discovered in the early 1890s but received little attention until it was found by University of Portsmouth
University of Portsmouth
The University of Portsmouth is a university in Portsmouth, Hampshire, England. The University was ranked 60th out of 122 in The Sunday Times University Guide...
student Mike Taylor
Mike Taylor (paleontologist)
Mike Taylor is a British computer programmer and amateur paleontologist. To date, he has published 13 paleontological papers and is co-credited with naming 2 dinosaur species .Along with paleontologists Darren Naish and Matt Wedel, he founded the paleontology blog .- References :...
, who formally described and named it in 2007 with Darren Naish
Darren Naish
Darren Naish is a vertebrate palaeontologist and science writer. He obtained a geology degree at the University of Southampton and later studied vertebrate palaeontology under British palaeontologist David Martill at the University of Portsmouth, where he obtained both an M. Phil...
.
Description
Xenoposeidon is based onHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
BMNH
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...
R2095, a partial posterior
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
back vertebra. The specimen lacks the anterior face of the centrum
Body of vertebra
The body is the largest part of a vertebra, and is more or less cylindrical in shape. For vertebrates other than humans, this structure is usually called a centrum....
and the upper portion of the neural arch
Vertebral arch
The vertebral arch is the posterior part of a vertebra.It consists of a pair of pedicles and a pair of laminae, and supports seven processes:* four articular processes* two transverse processes* one spinous process...
. The centrum is estimated at 200 millimetres (7.9 in) long, and the height of the preserved portion of the vertebra is 300 millimetres (11.8 in). The average diameter of the posterior face of the centrum is 165 millimetres (6.50 in), with a concave surface. This concavity is deep enough to suggest that the anterior faces of vertebrae from this part of the dinosaur's spine would have been convex to articulate with such a shape.
The specimen displays several distinguishing characteristics. The base of the neural arch covers the length of the centrum and is continuous with the centrum's posterior face. The neural arch leans anteriorly at 35° and there are broad areas of featureless bone on the lateral surfaces of the arch. The neural canal
Vertebral foramen
In a typical vertebra, the vertebral foramen is the foramen formed by the anterior segment , and the posterior part, the vertebral arch....
is large and teardrop-shaped anteriorly but small and circular at its posterior opening. The various bony struts and sheets that make up the arch have a distinctive configuration.
Classification
Xenoposeidons distinct suite of vertebral characteristics is unlike those found in other groups of sauropods, which differ in various proportional and structural features. So unique is the vertebra that when Taylor and Naish attempted to classify it using a phylogeneticPhylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
analysis
Computational phylogenetics
Computational phylogenetics is the application of computational algorithms, methods and programs to phylogenetic analyses. The goal is to assemble a phylogenetic tree representing a hypothesis about the evolutionary ancestry of a set of genes, species, or other taxa...
, they found that, although a neosauropod
Neosauropoda
Neosauropoda is a division-level clade of sauropods within Dinosauria, and consists of the group leading to Diplodocoidea and Macronaria. Haplocanthosaurus was a typical basal neosauropod from around 150 million years ago, in the Late Jurassic...
, it didn’t fit ‘comfortably’ into any of the established groups, Diplodocoidea
Diplodocoidea
Diplodocoidea was a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like Supersaurus, Diplodocus, Apatosaurus, and Amphicoelias...
, Camarasauridae, Brachiosauridae
Brachiosauridae
Brachiosauridae are a family of dinosaurs, whose members are known as brachiosaurids. They were herbivorous quadrupeds with longer forelegs than hind legs - the name derives from the Greek for arm lizard - and long necks...
and Titanosauria. Xenoposeidon could be a derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
member of one of the known groups, or may even represent a new group. The authors left it as a neosauropod of uncertain affinities
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
.
Discovery and history
Fossil collector Phillip James Rufford discovered the vertebra that would be later named Xenoposeidon in the early 1890s. It was found near HastingsHastings
Hastings is a town and borough in the county of East Sussex on the south coast of England. The town is located east of the county town of Lewes and south east of London, and has an estimated population of 86,900....
in East Sussex
East Sussex
East Sussex is a county in South East England. It is bordered by the counties of Kent, Surrey and West Sussex, and to the south by the English Channel.-History:...
, England, in rocks of the Hastings Bed Group. This formation
Rock formation
This is a list of rock formations that include isolated, scenic, or spectacular surface rock outcrops. These formations are usually the result of weathering and erosion sculpting the existing rock...
dates to the Lower Cretaceous, and is within the Berriasian
Berriasian
In the geological timescale, the Berriasian is an age or stage of the Early or Lower Creteceous. It is the oldest or lowest subdivision in the entire Cretaceous. It spanned between 145.5 ± 4.0 Ma and 140.2 ± 3.0 Ma...
and Valanginian
Valanginian
In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 140.2 ± 3.0 Ma and 136.4 ± 2.0 Ma...
Stages
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
. The vertebra was probably from the Berriasian portion of the Ashdown Beds Formation within the Hastings, although precise information about the locality and stratigraphy have been lost if such data were ever recorded.
The partial posterior
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
back vertebra, cataloged as BMNH R2095, was briefly described by English naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
and paleontologist Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
in 1893. He thought that it might belong to Cetiosaurus
Cetiosaurus
Cetiosaurus meaning 'whale lizard', from the Greek cetus/κητος meaning 'sea monster' and saurus/σαυρος meaning 'lizard', was a sauropod dinosaur from the Mid to Late Jurassic Period in what are now Europe and Africa. It is estimated to have been about long and to have weighed roughly...
brevis, better known today as Pelorosaurus conybearei
Pelorosaurus
Pelorosaurus was a huge plant-eating dinosaur. Pelorosaurus was one of the first sauropod dinosaurs ever discovered. Pelorosaurus lived during the Early Cretaceous period, about 138-112 million years ago. Fossils referred to Pelorosaurus have been found in England and Portugal...
. The bone attracted little attention for decades, sitting on a shelf at the British Natural History Museum
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...
in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
for 113 years. Mike Taylor, a sauropod vertebra specialist, stumbled upon it and became interested in the unusual specimen, entering into a description of it with Darren Naish.
The new genus was first announced by the British Palaeontological Association on November 15, 2007. The genus consists of the single species Xenoposeidon proneneukos. The species name means ‘forward sloping’, in recognition of the anterior sloping of the neural arch
Vertebral arch
The vertebral arch is the posterior part of a vertebra.It consists of a pair of pedicles and a pair of laminae, and supports seven processes:* four articular processes* two transverse processes* one spinous process...
. This unusual characteristic, along with its other distinctive features, prompted the authors to erect the new genus.
Paleobiology
Like other sauropods, Xenoposeidon would have been a large quadrupedQuadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
. It was relatively small for a sauropod. Extrapolating from the vertebra suggests that the type
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
individual of Xenoposeidon could have been about 15 metres (50 ft) long and weighed approximately 7.6 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s (8.4 short ton
Short ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...
s), if it resembled Brachiosaurus
Brachiosaurus
Brachiosaurus is a genus of sauropod dinosaur from the Jurassic Morrison Formation of North America. It was first described by Elmer S. Riggs in 1903 from fossils found in the Grand River Canyon of western Colorado, in the United States. Riggs named the dinosaur Brachiosaurus altithorax,...
, to 20 m (65 ft) long and 2.8 tonnes (3.1 short tons), if it was built like the longer, lighter Diplodocus
Diplodocus
Diplodocus , or )is a genus of diplodocid sauropod dinosaur whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a Neo-Latin term derived from Greek "double" and "beam", in reference to its double-beamed chevron bones...
.