Rhomaleosaurus Seeley, 1874
Rhomaleosaurus is the largest known Lower Jurassic pliosaur and was the top predator in early Jurassic marine ecosystems. It has a reinforced skull to help resist torsion and a ferocious set of teeth, a combination perfect for snatching and killing cephalopods, fish, and other marine reptiles. Historically, the genus Rhomaleosaurus has been interchangeable with now invalid 'Thaumatosaurus'. See my blog article Whatever happened to 'Thaumatosaurus'? for more information.
Several species previosuly referred to Rhomaleosaurus are now classified as distinct genera or junior synonyms of other species of Rhomaleosaurus. The species 'Rhomaleosaurus'/'Thaumatosaurus' victor (Fraas, 1910) was recently described as a new genus, Meyerasaurus. The species 'Rhomaleosaurus' longirostris (Blake, 1876) is now regarded as a seperate species of Hauffiosaurs (Benson et. al. 2011)
The type specimen of Rhomaleosaurus (R. cramptoni) is held in the National Museum of Ireland (Natural History) and remains to this day the largest complete pliosaur ever discovered.
Classification
Sauropterygia --> Eosauropterygia --> Eusauropterygia --> Pistosauroidea --> Plesiosauria --> Pliosauroidea --> Rhomaleosauridae
R. cramptoni (Tate and Blake, 1863)
R. cramptoni is the type species of Rhomaleosaurus.
The complicated history of Rhomaleosaurus cramptoni
In 1848, the fossil skeleton of R. cramptoni was unearthed by workers in an Alum quarry at Kettleness on the Yorkshire coast. The magnificent fossil was secured for five years at Mulgrave Castle, the home of the Marquis of Normanby, owner of the quarry. But the specimen was soon to move home - to Ireland. The Marquis presented the fossil in 1853 to his friend Sir Philip Crampton who brought the specimen to Dublin to be displayed as centrepiece at the 1853 British Association annual meeting. A specially constructed building was created by the Zoological Society of Ireland to accommodate the huge specimen, and the fossil found a temporary home. In 1863 the specimen was loaned for display in the Royal Dublin Society museum and was scientifically described and named. The Royal Dublin Society museum was incorporated into what is now known as the National Museum of Ireland in 1877. At the time of transfer to a state owned museum in 1877 the 'Science and Art Museum, Dublin' as it was then known, paid 200 pounds to acquire the specimen permanently. In 1890, the fossil moved again to another building, into the museum's 'fossil hall'. But in 1962 the hall beside the Natural History Museum on Merrion Street was demolished and the specimen was transferred to storage. The collection was moved yet again in 1992 to the National Museum of Ireland (Natural History) reserve stores at Beggars Bush, where the giant reptile currently resides. (Thanks to Nigel Monaghan for correcting some historical details.)
Material
NMING F8785, a complete skeleton exposed in dorsal view. The skull is prepared in three dimensions.
Casts
A number of casts were made of the fossil throughout its history, probably purchased from Henry. A. Ward, who dealt in replica fossils including Rhomaleosaurus cramptoni, throughout the late 1800s. Specimens are on display in Bath, London and New York (Smith, 2006). Many casts are unique in some aspects. Look closely (see above), and you will notice that the two forelimbs are identical copies of each other in the Bath cast. To add extra confusion, this duplicated limb is in the wrong place - it is actually a hindlimb - the two hindlimbs in the cast are really forelimbs placed in the wrong sockets. The London specimen is also unique, a new set of limbs have replaced the original ones which were mounted wrongly.
Age and Location
Hildoceras bifrons zone, Alum Shale, Toarcian, Lower Jurassic, Whitby, Yorkshire, England.
R. cramptoni images
R. zetlandicus Phillips, 1854
Mike Taylor studied the holotype of R. zetlandicus for his Ph.D. thesis and subsequently published a description of the cranial anatomy (Taylor, 1992). Vincent and Smith (2010) referred the holotype of R. propinquus to R. zetlandicus
Material
The holotype (YM G503) is a partial skeleton, on display in the Yorkshire Museum. Referred material includes WM 851.S ('Plesiosaurus propinquus'), on display in the Whitby Museum
Age and Location
Alum Shale, Toarcian, Lower Jurassic, Whitby, Yorkshire, England.
R. zetlandicus images
R. thorntoni
under construction
'Rhomaleosaurus' megacephalus Stutchbury, 1846
According to recent studies Rhomaleosaurus megacephalus deserves generic separation from Rhomaleosaurus (Smith and Dyke, 2008). 'R' megacephalus is closely related toEurycleidus. and some authors have regarded 'R.' megacephalus as a distinct species of Eurycleidus. The original holotype specimen was housed in the Bristol Museum and Art Gallery but was destroyed during the Second World War. Some casts of the skull and one forelimb exist today.
The replacement neotype specimen of 'R'. megacephalus is nicknamed the 'Barrow Kipper' (Taylor and Martin, 1990) after the place it was discovered, and can be seen on display at the New Walk Museum in Leicester, UK. The skull was described extensively by Cruikshank (1994b) and can be seen on display at the New Walk Museum in Leicester, UK. Cruickshank et al. (1991) proposed a specilaized plesiosaur olfaction ('smelling') system based on 'Rhomaleosaurus' megacephalus, and it may be an adaptation common in Plesiosauria (Brown and Cruickshank, 1994). The anteriorly placed internal nostrils on the palate have grooves that may have channelled water. The flow would have been maintained by hydrodynamic pressure over the posteriorly placed external nares (on the top of the skull) as the animal swam. During its passage through the nasal ducts, the water would have been 'tasted' by olfactory epithelia.
Material
Neotype, LEICT G221.1851, complete skeleton. Holotype (now destroyed), complete specimen. There are several referred specimens including complete skeletons See Smith (2007)
Age and Location
Early Hettangian, Lower Jurassic, Barrow-upon-Soar, Leicestershire, England.
'Rhomaleosaurus' megacephalus images
