Rhomaleosaurus
Encyclopedia
Rhomaleosaurus is an extinct genus
of Early Jurassic
(Toarcian
age
, about 183 to 175.6 million years ago) rhomaleosaurid pliosauroid known from Northamptonshire
and from Yorkshire
of the United Kingdom
. It was first named by Harry Seeley
in 1874
and the type species
is Rhomaleosaurus cramptoni. It was one of the earliest and large marine reptile predators which hunted in the seas of Mesozoic era. Its length was about 7 m (23 ft) long. Like other pliosaurs, Rhomaleosaurus fed on ichthyosaurs, ammonites and other plesiosaurs
.
, dating to the early Toarcian
age, about 183 to 180 million years ago. The complete skeleton
which preserved the skull
, NMING
F8785, was kept for five years at Mulgrave Castle, which was then owned by the Marquess of Normanby
. In 1853, the Marquess introduced the interesting finding to the eminent Irish surgeon and anatomist, Sir Philip Crampton
. The same year, Crampton transferred the fossil to Dublin to be displayed as a centrepiece at the 1853 British Association annual meeting. The Zoological Society of Ireland
built a specially constructed building to house the large reptile. After a decade, still remaining undescribed, the specimen moved in the Royal Dublin Society
museum and officially described by Alexander Carte and W. H. Bailey as a new species of Plesiosaurus
. Carte and Bailey named the species Plesiosaurus cramptoni after the Irish scientist, Sir Philip Crampton. In 1874, the British geologist Harry G. Seeley
, based on this finding, which is now known as the holotype
of the family Rhomaleosauridae
, recognized and erected a new genus establishing Rhomaleosaurus. Only in 2006 the skull
of this specimen was finally prepared and enabled a restudy of this genus.
WM
852.S, articulate
d almost complete skeleton
which preserved the skull
, exposed in dorsal view. It was collected from the A. serpentines ammonoid zone, of the Whitby Mudstone Formation
, dating to the middle Toarcian stage, about 180-177 million years ago. R. propinquus was first named by Tate and Blake in 1876
as a new species of Plesiosaurus
. Watson (1910) redescribed it as a species of Rhomaleosaurus. Adam S. Smith (2007), in his thesis on the anatomy and classification of the family Rhomaleosauridae
, suggested that R. propinquus, is a junior synonym of Rhomaleosaurus zetlandicus. Smith and Gareth J. Dyke (2008) considered this species to be valid.
BMNH
R4853, three-dimensional, partially complete skeleton which preserved most of the skull and mandible
s. It was collected from Kingsthorp of Northamptonshire
, dating to the Toarcian stage. It is the only well-known British Toarcian rhomaleosaurid discovered away from the Yorkshire coast, to date. R. thorntoni was first named by Andrews in 1922
and later revised by Cruickshank (1996) as a junior synonym of R. cramptoni, alongside with R. zetlandicus. Adam S. Smith (2007) and Smith and Gareth J. Dyke (2008) considered this species to be valid.
YORYM
G503, a nearly complete skull and vertebral column
in association with parts of the limb
s. It was collected from the Alum Shale of Whitby Mudstone Formation, Yorkshire, dating to the Toarcian stage. R. thorntoni was first named by Phillips in 1854
and its skull was described in detail by Taylor (1992). Later it was revised by Cruickshank (1996) as a junior synonym of R. cramptoni, alongside with R. thorntoni. Adam S. Smith (2007) and Smith and Gareth J. Dyke (2008) considered this species to be valid.
, the genus Rhomaleosaurus has only three valid species: R. cramptoni, R. thorntoni and R. zetlandicus. Smith and Dyke (2008) also recognized R. propinquus as valid. Other species that previously fell under this genus were: R. megacephalus and R. victor. Smith (2007) and Smith and Dyke (2008) pointed out that these species do not belong to Rhomaleosaurus, as R. megacephalus is referred to Eurycleidus
(or to a new genus by Smith and Dyke (2008)) and R. victor represents a new genus named Meyerasaurus
by Smith and Vincent in 2010. Cladistic analyses by Ketchum & Benson, 2010, Benson et al., 2011 and Ketchum & Benson, 2011 found R. megacephalus to be basal to the clade containing Rhomaleosaurus and Eurycleidus, thus it should be in its own, yet unnamed, genus as suggested by Smith and Dyke (2008).
, back in 1841. Meyer described the species Thaumatosaurus oolithicus based on partial skull, vertebral and limb remains, that found in the Posidonia Shale
of Holzmaden
, Baden-Württemberg
, Germany
. In 1856, Meyer published a full description of Thaumatosaurus and later provided figures of the specimen. Richard Lydekker
(1889) regarded Rhomaleosaurus as a synonym of Thaumatosaurus because Richard Lydekker
and Harry G. Seeley "refused steadfastly to recognize the generic and specific names proposed by one another". Lydekker referred continuously to the name Thaumatosaurus, instead of Rhomaleosaurus. Fraas (1910) recognized both generic names in his original description of R. victor (now Meyerasaurus
), but referring to the new species "Thaumatosaurus" victor. Many other researchers adopted the name "Thaumatosaurus". Today this taxon is regarded as a nomen dubium
because the holotype can be referred to Pliosauroidea indet at best. The diagnostic specimens which previously were regarded as Thaumatosauruss specimens, are now represent the holotypes of Eurycleidus
, Meyerasaurus
and Rhomaleosaurus.
below follows Smith & Dyke, 2008.
species.
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 Early Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
(Toarcian
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age or stage in the Early or Lower Jurassic. It spans the time between 183.0 Ma and 175.6 Ma...
age
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...
, about 183 to 175.6 million years ago) rhomaleosaurid pliosauroid known from Northamptonshire
Northamptonshire
Northamptonshire is a landlocked county in the English East Midlands, with a population of 629,676 as at the 2001 census. It has boundaries with the ceremonial counties of Warwickshire to the west, Leicestershire and Rutland to the north, Cambridgeshire to the east, Bedfordshire to the south-east,...
and from Yorkshire
Yorkshire
Yorkshire is a historic county of northern England and the largest in the United Kingdom. Because of its great size in comparison to other English counties, functions have been increasingly undertaken over time by its subdivisions, which have also been subject to periodic reform...
of the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. It was first named by Harry Seeley
Harry Seeley
Harry Govier Seeley was a British paleontologist.-Career:Seeley was born in London, the son of Richard Hovill Seeley, goldsmith, and his second wife Mary Govier. He attended classes at the Royal School of Mines, Kensington before becoming an assistant to Adam Sedgwick at the Woodwardian Museum,...
in 1874
1874 in paleontology
-Newly named dinosaurs:-New taxa:-Newly named pterosaurs:-new taxa:...
and 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...
is Rhomaleosaurus cramptoni. It was one of the earliest and large marine reptile predators which hunted in the seas of Mesozoic era. Its length was about 7 m (23 ft) long. Like other pliosaurs, Rhomaleosaurus fed on ichthyosaurs, ammonites and other plesiosaurs
Plesiosauria
Plesiosauria is an order of Mesozoic marine reptiles. Plesiosaurs first appeared in the Early Jurassic Period and became especially common during the Jurassic Period, thriving until the K-T extinction at the end of the Cretaceous Period.The name "plesiosaur" is used to refer to the order...
.
R. cramptoni
In July 1848, a fossil of a large plesiosaur was unearthed in an Alum quarry at Kettleness, near Whitby, in Yorkshire, England. It was collected from the A. bifrons ammonite zone of the Whitby Mudstone FormationWhitby Mudstone Formation
The Whitby Mudstone Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.-See also:* List of dinosaur-bearing rock formations...
, dating to the early Toarcian
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age or stage in the Early or Lower Jurassic. It spans the time between 183.0 Ma and 175.6 Ma...
age, about 183 to 180 million years ago. The complete skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
which preserved the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
, NMING
National Museum of Ireland
The National Museum of Ireland is the national museum in Ireland. It has three branches in Dublin and one in County Mayo, with a strong emphasis on Irish art, culture and natural history.-Archaeology:...
F8785, was kept for five years at Mulgrave Castle, which was then owned by the Marquess of Normanby
Marquess of Normanby
Marquess of Normanby is a title that has been created twice, once in the Peerage of England and once in the Peerage of the United Kingdom.The first creation came in 1694 in the Peerage of England in favour of John Sheffield, 3rd Earl of Mulgrave KG...
. In 1853, the Marquess introduced the interesting finding to the eminent Irish surgeon and anatomist, Sir Philip Crampton
Sir Philip Crampton
Sir Philip Crampton, 1st Baronet, FRS was an eminent Irish surgeon and anatomist.-Life:Crampton was born in Dublin, Ireland, the son of a dentist. He was a childhood friend of Theobald Wolfe Tone, the United Irishman, and a cousin, on his mother's side, of Thomas Verner, Grand Master of the Orange...
. The same year, Crampton transferred the fossil to Dublin to be displayed as a centrepiece at the 1853 British Association annual meeting. The Zoological Society of Ireland
Zoological Society of Ireland
The Zoological Society of Ireland is the body responsible for running Dublin Zoo, where it is based, and Fota Wildlife Park in County Cork...
built a specially constructed building to house the large reptile. After a decade, still remaining undescribed, the specimen moved in the Royal Dublin Society
Royal Dublin Society
The Royal Dublin Society was founded on 25 June 1731 to "to promote and develop agriculture, arts, industry, and science in Ireland". The RDS is synonymous with its main premises in Ballsbridge in Dublin, Ireland...
museum and officially described by Alexander Carte and W. H. Bailey as a new species of Plesiosaurus
Plesiosaurus
Plesiosaurus was a genus of large marine sauropterygian reptile that lived during the early part of the Jurassic Period, and is known by nearly complete skeletons from the Lias of England...
. Carte and Bailey named the species Plesiosaurus cramptoni after the Irish scientist, Sir Philip Crampton. In 1874, the British geologist Harry G. Seeley
Harry Seeley
Harry Govier Seeley was a British paleontologist.-Career:Seeley was born in London, the son of Richard Hovill Seeley, goldsmith, and his second wife Mary Govier. He attended classes at the Royal School of Mines, Kensington before becoming an assistant to Adam Sedgwick at the Woodwardian Museum,...
, based on this finding, which is now known as the holotype
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...
of the family Rhomaleosauridae
Rhomaleosauridae
Rhomaleosauridae is a family of extinct reptiles in the Plesiosauria order. It includes the Macroplata, Maresaurus, Rhomaleosaurus, Yuzhoupliosaurus and Meyerasaurus genera....
, recognized and erected a new genus establishing Rhomaleosaurus. Only in 2006 the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
of this specimen was finally prepared and enabled a restudy of this genus.
R. propinquus
R. propinquus is known from the holotypeHolotype
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...
WM
Whitby Museum
Whitby Museum is a private museum in Whitby, North Yorkshire, England, run by Whitby Literary and Philosophical Society, a learned society and registered charity, established in 1823....
852.S, articulate
Articulate
Articulate may refer to:*Articulate *Articulate sign*Articulate sound*Joint, also known as articulation*Word modified by an article...
d almost complete skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
which preserved the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
, exposed in dorsal view. It was collected from the A. serpentines ammonoid zone, of the Whitby Mudstone Formation
Whitby Mudstone Formation
The Whitby Mudstone Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.-See also:* List of dinosaur-bearing rock formations...
, dating to the middle Toarcian stage, about 180-177 million years ago. R. propinquus was first named by Tate and Blake in 1876
1876 in paleontology
-Dinosaurs:-New taxa:-Non-mammalian:...
as a new species of Plesiosaurus
Plesiosaurus
Plesiosaurus was a genus of large marine sauropterygian reptile that lived during the early part of the Jurassic Period, and is known by nearly complete skeletons from the Lias of England...
. Watson (1910) redescribed it as a species of Rhomaleosaurus. Adam S. Smith (2007), in his thesis on the anatomy and classification of the family Rhomaleosauridae
Rhomaleosauridae
Rhomaleosauridae is a family of extinct reptiles in the Plesiosauria order. It includes the Macroplata, Maresaurus, Rhomaleosaurus, Yuzhoupliosaurus and Meyerasaurus genera....
, suggested that R. propinquus, is a junior synonym of Rhomaleosaurus zetlandicus. Smith and Gareth J. Dyke (2008) considered this species to be valid.
R. thorntoni
R. thorntoni is known from the holotypeHolotype
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
BMNH
BMNH may refer to:*British Museum of Natural History, commonly known as Natural History Museum, in London, the United Kingdom*Beijing Museum of Natural History, in Beijing, China...
R4853, three-dimensional, partially complete skeleton which preserved most of the skull and mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
s. It was collected from Kingsthorp of Northamptonshire
Northamptonshire
Northamptonshire is a landlocked county in the English East Midlands, with a population of 629,676 as at the 2001 census. It has boundaries with the ceremonial counties of Warwickshire to the west, Leicestershire and Rutland to the north, Cambridgeshire to the east, Bedfordshire to the south-east,...
, dating to the Toarcian stage. It is the only well-known British Toarcian rhomaleosaurid discovered away from the Yorkshire coast, to date. R. thorntoni was first named by Andrews in 1922
1922 in paleontology
-Insects:-Newly named dinosaurs:Data courtesy of George Olshevsky's dinosaur genera list and Dr. Jeremy Montague's dinosaur genus database.-New taxa:-Non-mammalian:...
and later revised by Cruickshank (1996) as a junior synonym of R. cramptoni, alongside with R. zetlandicus. Adam S. Smith (2007) and Smith and Gareth J. Dyke (2008) considered this species to be valid.
R. zetlandicus
R. zetlandicus is known from the holotypeHolotype
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...
YORYM
Yorkshire Museum
The Yorkshire Museum is a museum in York, England. It is the home of the Cawood sword, and has four permanent collections, covering biology, geology, archaeology and astronomy...
G503, a nearly complete skull and vertebral column
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
in association with parts of the limb
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....
s. It was collected from the Alum Shale of Whitby Mudstone Formation, Yorkshire, dating to the Toarcian stage. R. thorntoni was first named by Phillips in 1854
1854 in paleontology
-Newly named dinosaurs:-Newly named plesiosaurs:-Non-mammalian:...
and its skull was described in detail by Taylor (1992). Later it was revised by Cruickshank (1996) as a junior synonym of R. cramptoni, alongside with R. thorntoni. Adam S. Smith (2007) and Smith and Gareth J. Dyke (2008) considered this species to be valid.
Other Species
Through the years, various species have been referred to as Rhomaleosaurus. However, according to Smith (2007), in his thesis on the anatomy and classification of the family RhomaleosauridaeRhomaleosauridae
Rhomaleosauridae is a family of extinct reptiles in the Plesiosauria order. It includes the Macroplata, Maresaurus, Rhomaleosaurus, Yuzhoupliosaurus and Meyerasaurus genera....
, the genus Rhomaleosaurus has only three valid species: R. cramptoni, R. thorntoni and R. zetlandicus. Smith and Dyke (2008) also recognized R. propinquus as valid. Other species that previously fell under this genus were: R. megacephalus and R. victor. Smith (2007) and Smith and Dyke (2008) pointed out that these species do not belong to Rhomaleosaurus, as R. megacephalus is referred to Eurycleidus
Eurycleidus
Eurycleidus is an extinct genus of plesiosaur. The type species is E. arcuatus, which lived during the Hettangian age . Like other plesiosaurs, Eurycleidus probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful...
(or to a new genus by Smith and Dyke (2008)) and R. victor represents a new genus named Meyerasaurus
Meyerasaurus
Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southeastern Germany.-Description:Meyerasaurus is known from the holotype SMNS 12478, articulated and complete skeleton which preserved the skull, exposed in ventral view. The skull has a length of ,...
by Smith and Vincent in 2010. Cladistic analyses by Ketchum & Benson, 2010, Benson et al., 2011 and Ketchum & Benson, 2011 found R. megacephalus to be basal to the clade containing Rhomaleosaurus and Eurycleidus, thus it should be in its own, yet unnamed, genus as suggested by Smith and Dyke (2008).
Confusion with Thaumatosaurus
The name Thaumatosaurus, which means 'wonder reptile', belonged to a genus of plesiosaur that was described by palaeontologist Christian Erich Hermann von MeyerChristian Erich Hermann von Meyer
Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...
, back in 1841. Meyer described the species Thaumatosaurus oolithicus based on partial skull, vertebral and limb remains, that found in the Posidonia Shale
Posidonia Shale
The Posidonia Shale is a Lower Jurassic geological formation famous for its exceptionally well-preserved complete skeletons of fossil marine fish and reptiles. The Posidonienschiefer as German paleontologists call it, takes its name from the ubiquitous fossils of Posidonia bronni that characterize...
of Holzmaden
Holzmaden
Holzmaden is a town in Baden-Württemberg, Germany that lies between Stuttgart and Ulm.The ground in and around the city contains rich layers of well preserved fossils of the Jurassic period. The fossils are found in the 160 million year old Posidonia Shale and displayed in the local Museum Hauff...
, Baden-Württemberg
Baden-Württemberg
Baden-Württemberg is one of the 16 states of Germany. Baden-Württemberg is in the southwestern part of the country to the east of the Upper Rhine, and is the third largest in both area and population of Germany's sixteen states, with an area of and 10.7 million inhabitants...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. In 1856, Meyer published a full description of Thaumatosaurus and later provided figures of the specimen. Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
(1889) regarded Rhomaleosaurus as a synonym of Thaumatosaurus because Richard Lydekker
and Harry G. Seeley "refused steadfastly to recognize the generic and specific names proposed by one another". Lydekker referred continuously to the name Thaumatosaurus, instead of Rhomaleosaurus. Fraas (1910) recognized both generic names in his original description of R. victor (now Meyerasaurus
Meyerasaurus
Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southeastern Germany.-Description:Meyerasaurus is known from the holotype SMNS 12478, articulated and complete skeleton which preserved the skull, exposed in ventral view. The skull has a length of ,...
), but referring to the new species "Thaumatosaurus" victor. Many other researchers adopted the name "Thaumatosaurus". Today this taxon is regarded as a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
because the holotype can be referred to Pliosauroidea indet at best. The diagnostic specimens which previously were regarded as Thaumatosauruss specimens, are now represent the holotypes of Eurycleidus
Eurycleidus
Eurycleidus is an extinct genus of plesiosaur. The type species is E. arcuatus, which lived during the Hettangian age . Like other plesiosaurs, Eurycleidus probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful...
, Meyerasaurus
Meyerasaurus
Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southeastern Germany.-Description:Meyerasaurus is known from the holotype SMNS 12478, articulated and complete skeleton which preserved the skull, exposed in ventral view. The skull has a length of ,...
and Rhomaleosaurus.
Phylogeny
Smith & Dyke, 2008 redescribed the skull of R. cramptoni after its final preperation. Both Rhomaleosauridae and Pliosauridae were found to be monophyletic, and the relations between Rhomaleosauruss species were tested. The cladogramCladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
below follows Smith & Dyke, 2008.
Paleobiology
Rhomaleosaurus may have been able to pick up scents while submerged by forcing water through passages in its skull containing sensory organs. This adaptation would have enabled it to hunt its prey in a similar manner to some modern sharkShark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
species.