By Aodhán Ó Gogáin, Inventory Assistant, National Museum of Ireland
Copyright © 2023 Aodhán Ó Gogáin
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Centre stage in the fossil marine reptile gallery of London’s Natural History Museum is a complete skeleton of the plesiosaur Rhomaleosaurus cramptoni (Figure 1 at page end). However, the London specimen is a replica. The real skeleton of R. cramptoni belongs to the National Museum of Ireland (NMI) and is currently in Museum storage.
History of the specimen
The original Rhomaleosaurus cramptoni was excavated in 1848 from 180-million-year-old Lower Jurassic rocks of the Whitby Mudstone Formation. These rocks are near Whitby, along the north Yorkshire coast of England. The fossil was first housed at Mulgrave Castle, owned by the Marquess of Normanby, and subsequently presented to eminent Irish surgeon and anatomist Sir Philip Crampton who brought it to Dublin. There, it formed the centrepiece of the 1853 British Association Annual Meeting.
During this time the specimen was loaned, and then bequeathed, to the Zoological Society of Ireland (ZSI), who constructed a tent-like shelter at the former Botanical Gardens (now Dublin Zoo) to house the specimen. However, this shelter was inadequate and left the fossil marine reptile exposed to the elements. The ZSI realised they could not keep it, so in 1861, it was loaned to the Royal Dublin Society and put on display in 1863. When the Royal Dublin Society collections transferred to the NMI in 1877, the NMI purchased the specimen of R. cramptoni from the ZSI for £100.
The specimen was displayed in the Museum’s fossil hall from 1890 until 1962, when it was removed so the hall could be demolished to accommodate new buildings for the Oireachtas, including the Dáil Bar and Restaurant. After the destruction of the hall, the R. cramptoni specimen was stored in the midlands until the 1990s, and it has lived in Dublin since that time.
What sort of animal was Rhomaleosaurus cramptoni?
Rhomaleosaurus cramptoni was a type of plesiosaur. The plesiosaurs were a group of marine reptiles that lived during the Jurassic and Cretaceous Periods (spanning from 201 to 66 million years ago) and had bodies with elongated necks, relatively small heads, and short stout tails. One group of plesiosaurs, the pliosaurs, had short necks and large heads. R. cramptoni was, technically, a pliosaur, but was unique in having a long neck and a relatively large head (Figure 2). The fore- and hind limbs of plesiosaurs were modified into wing-like flippers, which were used to propel themselves through the water.
R. cramptoni lived during the early Jurassic Period and represents a more primitive plesiosaur body plan. Measuring a total of 7m in length and with a mouth full of large conical teeth, perfectly adapted for catching aquatic prey, R. cramptoni would have been a top predator in the Jurassic seas, preying on belemnites (relations of squids), fish, ichthyosaurs (dolphin-like marine reptiles) and other smaller plesiosaurs.
What is a type specimen?
A type specimen is an individual animal specimen on which the description and name of a new animal species is based. These important specimens are stored in museum collections and are available for inspection by researchers and can support future work on those taxonomic groups.
Scientific importance of Rhomaleosaurus cramptoni
The R. cramptoni in the NMI is the type specimen for this species and has the museum catalogue number NG:F8785. This species is important for both understanding plesiosaur evolution and for defining plesiosaur taxonomy. The most extensive research on the specimen was done by Dr Adam Smith for his 2007 PhD thesis in University College Dublin. As part of this project, a fossil preparator freed critical elements of the skull from the enclosing rock matrix (Figure 3), allowing Dr Smith to make a thorough anatomical and taxonomical description. It is the NMI’s wish to, one day, have the entire original skeleton prepared, described, and put on display.
Learn more
Ward, H. A. 1866. Catalogue of casts of fossils, from the principle museums of Europe and America, with short descriptions and illustrations. Benton and Andrews, Rochester, New York, 228pp.
Smith, S. A. and Dyke, G. J. 2008. The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics. Naturwissenschaften, 95, 975–980.
Smith, A. S. 2007. Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). PhD thesis. University College Dublin, 278pp.
