Magnosaurus
Encyclopedia
Magnosaurus was a genus
of basal tetanuran theropod dinosaur
from the Middle Jurassic
of England
. It is based on fragmentary remains and has often been confused with or included in Megalosaurus
.
named Megalosaurus nethercombensis from a partial skeleton (OUM J12143) from the Aalenian
-Bajocian
-age Middle Jurassic
Inferior Oolite
, found in the nineteenth century by W. Parker near Nethercomb, north of Sherborne
, in Dorset
, England
. The material included partial dentaries, dorsal and caudal vertebrae, a partial ilium
, a partial right pubis
, internal casts of the femora
, and tibia
e, from a possibly juvenile
individual. Huene interpreted it as a more primitive species
of Megalosaurus
.
In 1926, he named the tooth
species Megalosaurus lydekkeri for a specimen, BMNH 41352, from the Lower Lias (Lower Jurassic) of England that Richard Lydekker
had first described in 1888. Finally, in 1932, he created the genus Magnosaurus for M. nethercombensis, referred M. lydekkeri to it, and created a third species, M. woodi, for the genus. M. woodi was based on a tibia (BMNH R.3542) from the Lower Lias, which he simultaneously and accidentally also named Sarcosaurus andrewsi
; the latter name was in 1956 by von Huene given priority. Even more confusing, in the same 1932 publication von Huene renamed Sarcosaurus woodi into Magnosaurus woodi.
Until the 1990s, the genus had been ignored as a species of Megalosaurus. However, with growing concern over what exactly is constituted by Megalosaurus, Magnosaurus has been generally separated as its own genus. Also, there are morphological differences
: for example, possible Megalosaurus tibiae are compressed at the far end, unlike those of Magnosaurus. Rauhut (2003) considered it and Eustreptospondylus
to be the same genus, because the two share a similarly expanded front tip of the dentary and enlarged third dentary tooth. He therefore renamed Eustreptospondylus oxoniensis a Magnosaurus oxoniensis but this has not been generally followed. Reviews have found it to most likely be a basal tetanuran, probably a megalosaurid. A detailed redescription by Roger Benson in 2010 concluded Magnosaurus was valid taxon, a megalosauroid
megalosaurid, and at about 175 million years old the oldest certain known member of the Tetanurae
.
The type species
of Eustreptospondylus and Sarcosaurus are also sometimes assigned to Magnosaurus. In such cases the combinations are:
al carnivore
of moderate size for a dinosaur. The most similar animals probably would be animals like Eustreptospondylus, Dubreuillosaurus
, and Afrovenator
. Paul (1988) roughly estimated the mass of the type individual as around 175 kg (386 lb), which would correspond to a length of roughly four metres (13.1 ft), judging by his estimates for the sizes of other theropods. Benson however, in 2010 gave a higher estimation of about half a tonne; the animal would have stood at over a metre at the hip.
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 basal tetanuran theropod 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 Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
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...
. It is based on fragmentary remains and has often been confused with or included in Megalosaurus
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...
.
History and taxonomy
In 1923, Friedrich von HueneFriedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
named Megalosaurus nethercombensis from a partial skeleton (OUM J12143) from the Aalenian
Aalenian
The Aalenian is a subdivision of the Middle Jurassic epoch/series of the geologic timescale that extends from about 175.6 Ma to about 171.6 Ma . It was preceded by the Toarcian and succeeded by the Bajocian.-Stratigraphic definitions:...
-Bajocian
Bajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
-age Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
Inferior Oolite
Inferior Oolite
The Inferior Oolite is a geological formation in Europe. It dates back to the Middle Jurassic.-Formation:The Inferior Oolite is an Oolitic limestone, a Sedimentary rock, meaning it was formed during lithication. The Inferior Oolite is rich in organic material...
, found in the nineteenth century by W. Parker near Nethercomb, north of Sherborne
Sherborne
Sherborne is a market town in northwest Dorset, England. It is sited on the River Yeo, on the edge of the Blackmore Vale, east of Yeovil. The A30 road, which connects London to Penzance, runs through the town. The population of the town is 9,350 . 27.1% of the population is aged 65 or...
, in Dorset
Dorset
Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...
, 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...
. The material included partial dentaries, dorsal and caudal vertebrae, a partial ilium
Ilium
-Places:* Ilion or, Latinized, Ilium, another name for the legendary city of Troy, hence the title of Homer's Iliad*Ilium , an ancient city in Epirus...
, a partial right pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....
, internal casts of the femora
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, and tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
e, from a possibly juvenile
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
individual. Huene interpreted it as a more primitive species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of Megalosaurus
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...
.
In 1926, he named the tooth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
species Megalosaurus lydekkeri for a specimen, BMNH 41352, from the Lower Lias (Lower Jurassic) of England that Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
had first described in 1888. Finally, in 1932, he created the genus Magnosaurus for M. nethercombensis, referred M. lydekkeri to it, and created a third species, M. woodi, for the genus. M. woodi was based on a tibia (BMNH R.3542) from the Lower Lias, which he simultaneously and accidentally also named Sarcosaurus andrewsi
Sarcosaurus
Sarcosaurus is a genus of theropod dinosaur, either a coelophysoid or a basal ceratosaur, roughly 3.5 meters long. It lived during the Sinemurian stage of the Early Jurassic, about 194 million years ago....
; the latter name was in 1956 by von Huene given priority. Even more confusing, in the same 1932 publication von Huene renamed Sarcosaurus woodi into Magnosaurus woodi.
Until the 1990s, the genus had been ignored as a species of Megalosaurus. However, with growing concern over what exactly is constituted by Megalosaurus, Magnosaurus has been generally separated as its own genus. Also, there are morphological differences
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
: for example, possible Megalosaurus tibiae are compressed at the far end, unlike those of Magnosaurus. Rauhut (2003) considered it and Eustreptospondylus
Eustreptospondylus
Eustreptospondylus is a genus of megalosaurid dinosaur, from the Callovian stage of the Middle Jurassic period in southern England, at a time when Europe was a series of scattered islands Eustreptospondylus ("well-curved vertebra", in reference to the arrangement of the spine in the original...
to be the same genus, because the two share a similarly expanded front tip of the dentary and enlarged third dentary tooth. He therefore renamed Eustreptospondylus oxoniensis a Magnosaurus oxoniensis but this has not been generally followed. Reviews have found it to most likely be a basal tetanuran, probably a megalosaurid. A detailed redescription by Roger Benson in 2010 concluded Magnosaurus was valid taxon, a megalosauroid
Megalosauroidea
Megalosauroidea is a group of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period.-Classification:...
megalosaurid, and at about 175 million years old the oldest certain known member of the Tetanurae
Tetanurae
Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early or middle Jurassic Period.-Definition:...
.
Other species
- M. lydekkeri is a dubious tooth genus, usually referred back to Megalosaurus as "M." lydekkeri.
- M. woodwardi is also dubious and was referred to ?Sarcosaurus andrewsi by Carrano and Sampson (2004).
The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of Eustreptospondylus and Sarcosaurus are also sometimes assigned to Magnosaurus. In such cases the combinations are:
- M. woodi for Sarcosaurus woodi.
- M. oxoniensis for Eustreptospondylus oxoniensis.
Paleobiology
Because the remains are sparse and fragmentary, details about the life and behaviour of Magnosaurus are unknown. It would have been a bipedBiped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
al carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
of moderate size for a dinosaur. The most similar animals probably would be animals like Eustreptospondylus, Dubreuillosaurus
Dubreuillosaurus
Dubreuillosaurus is a genus of carnivorous dinosaur from the middle Jurassic Period. It was a megalosaurid theropod. Its fossils were found in France....
, and Afrovenator
Afrovenator
Afrovenator is a genus of megalosaurid theropod dinosaur from the mid Jurassic Period of northern Africa. It was a bipedal predator, with a mouthful of sharp teeth and three claws on each hand...
. Paul (1988) roughly estimated the mass of the type individual as around 175 kg (386 lb), which would correspond to a length of roughly four metres (13.1 ft), judging by his estimates for the sizes of other theropods. Benson however, in 2010 gave a higher estimation of about half a tonne; the animal would have stood at over a metre at the hip.