Osmington Bay: Early Kimmeridgian, United Kingdom
collected by Kevan Sheehan 2001-2009

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
Reptilia - Plesiosauria - Pliosauridae
1 specimen
DORCM G.13,675, holotype skull
see common names

Geography
Country:United Kingdom State/province:England County:Dorset
Coordinates: 50.6° North, 2.4° West (view map)
Paleocoordinates:32.5° North, 13.3° East (Wright 2013)
Basis of coordinate:stated in text
Geographic resolution:small collection
Time
Period: Jurassic Epoch: Late Jurassic
Stage: Kimmeridgian 10 m.y. bin: Jurassic 5
Key time interval: Early Kimmeridgian Ammonoid zone:  Rasenia cymodoce
Age range of interval: 154.8 - 152.21 m.y. ago
Stratigraphy
Geological group:Ancholme Formation:Kimmeridge Clay
Stratigraphy comments: Wyke Siltstone bed (Rasenia cymodoce Zone, Lower Kimmeridgian), Kimmeridge Clay Formation, Ancholme Group of Osmington Bay (UK Ordnance Survey grid reference SY 372520 81930; Global Positioning System WGS84: 50° 38’ 11” N 2° 23’ 23” W), Dorset, United Kingdom (Fig. 1). The stratigraphic section at Black Head was given by (Cox & Gallois 1981:fig. 6).
Lithology and environment
Primary lithology: not reported
Environment:marine indet.
Taphonomy
Modes of preservation:body
Size of fossils:macrofossils
Collection methods and comments
Collection methods:surface (float),surface (in situ),mechanical,survey of museum collection
Reason for describing collection:taxonomic analysis
Collectors:Kevan Sheehan Collection dates:2001-2009
Collection method comments: DORCM, Dorset County Museum, DOrchester, Dorset, United Kingdom
DORCM G.13,675 was collected over a period of eight years as pieces up to 60 kg in mass weathered out of the sea-cliff. Most were collected by Kevan Sheehan, the owner of a small café overlooking the sea at Osmington Mills during daily walks along the foreshore. No permits were required for the collection of most of these pieces, which occurred in loose, fallen blocks in the intertidal zone. Other parts were collected in situ from privately owned land, and were purchased from the land owner.
Preparation of DORCM G.13,675 was undertaken between March 2010 and March 2011. The bulk of the matrix was removed using a modified Chicago pneumatic air pen. On areas where the matrix was particularly thick or where it was obvious that the underlying bone lay as a continuous sheet, a series of thin 5 mm deep slots were cut at 90 degrees to each other with a 40 mm diamond blade and the resulting blocks were chipped off using either an airpen or chisel. An airbrasive unit equipped with 50 micron aluminium oxide abrasive powder was used to remove the remaining matrix from the surface of the bone. The broken surface produced by the airpen made it difficult to identify the encrusting epifauna, so a 100 mm angle grinder fitted with a continuous diamond blade was used on these areas to grind away the matrix instead. The encrusting oysters appeared as a series of white circles within the grey matirx. This method proved very effective, because once the encrusting epifauna had been identified and delimited it was possible to finish the preparation of these areas with the airpen and airbrasive unit. The average mass of the sections making up the lower jaws was around 20 kg. The mass of the sections comprising the skull ranged from 15 kg upwards. Over 30 kg of matrix was removed from the block containing the orbits, after which this block weighed 50 kg. Load bearing breaks were bonded with the epoxy resin adhesive Araladite 2012. Preparation of the lower jaws took 200 hours and a further 365 hours were needed to complete preparation of the skull.
Metadata
Database number:145134
Authorizer:R. Benson Enterer:R. Benson
Modifier:J. Tennant Research group:vertebrate
Created:2013-05-27 22:46:16 Last modified:2025-02-22 15:12:02
Access level:the public Released:2013-05-27 22:46:16
Creative Commons license:CC0
Reference information

Primary reference:
46939. R. B. J. Benson, M. Evans, A. S. Smith, J. Sassoon, S. Moore-Faye, H. F. Ketchum, and R. Forrest. 2013. A giant pliosaurid skull from the Late Jurassic of England. PLoS ONE 8(5):e65989 [R. Benson/R. Benson/R. Benson]

Secondary references:

50860 D. Foffa, J. Sassoon, A. R. Cuff, M. N. Mavrogordato, and M. J. Benton. 2014. Complex rostral neurovascular system in a giant pliosaur. Naturwissenschaften [P. Mannion/J. Tennant]