Seven Rock Point (?): Sinemurian, United Kingdom
collected by Savage 1970

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
unclassified
Thalassionoides sp.
Crinoidea - Isocrinida - Pentacrinitidae
Pentacrinus sp. Miller 1821
nomen vanum belonging to Pentacrinites
Pentacrinus fragments
Reptilia - Plesiosauria
aff. Plesiosaurus dolichodeirus Conybeare 1824
1 specimen
BRSUG 26539, partial postcranial skeleton
Pisces
Pisces indet. Linnaeus 1758
synonym of Osteichthyes
fish vertebrae and a tooth
Cephalopoda - Ammonitida
Arietites ? bucklandi (Sowerby 1816)
original and current combination Ammonites bucklandi
arietitid ammonites ranging in size from 100-300 mm
unclassified
Chondrites sp. von Sternberg 1833
see common names

Geography
Country:United Kingdom State/province:England County:Dorset
Coordinates: 50.7° North, 2.9° West (view map)
Paleocoordinates:37.2° North, 3.0° East
Basis of coordinate:estimated from map
Geographic resolution:local area
Time
Period:Jurassic Epoch:Early/Lower Jurassic
Stage:Sinemurian 10 m.y. bin:Jurassic 1
Key time interval:Sinemurian Ammonoid zone: Arietites bucklandi
Age range of interval:199.50000 - 192.90000 m.y. ago
Stratigraphy
Geological group:Lias
Stratigraphic resolution:group
Stratigraphy comments: "...the nature of the Liassic sediment and its fossil biota enables the provenance of the specimen to be constrained to the Sinemurain stage of probably the Lyme Regis area..."
"The large size of the ammonites suggests they may belong to the Arietites bucklandi zone of the lowermost Sinemurian. However, the partial remains are not conlusive and further preparation is neccessary for specific identification of the ammonites. Arietitid ammonites are restricted to the Sinemurian, enabling the age of BRSUG 26539 to be constrained to this time period".
Lithology and environment
Primary lithology:gray,blue "limestone"
Lithology description: BRSUG 26539 is embedded in a 200mm thick bed of blue/grey lower Lias lomestone. This massive limestone lacks lamination and is well cemented. The sediment is highly bioturbated by branched and unbranched burrows of Chondrites, no bigger than 5mm in length and infilled with a light-grey limestone. These trace fossils are uniformly developed throughout the limestone bed, but are locally absent where the sediment has been bioturbated by large Thalassionoides burrows characterised by an increase in the concentration of fossil fragments, including a fish vertebra and tooth. Pentacrinus fragments and shelly debris. These crustacean burrows are coarsely branched structures up to 150 mm in length.
Environment:carbonate indet.
Geology comments: Chondrites represents dysaerobic to anaerobic consition, whereas the presence of Thalassionoides suggests higher levels of oxygenation (Ekdale & Mason 1988)... the presence of trace fossils and the disarticulated nature of the plesiosaur bones suggests that the palaeoenvironment was of a soft-ground substrate on the continental shelf above the storm-wave base
Taphonomy
Modes of preservation:body
Size of fossils:macrofossils
Collection methods and comments
Collection methods:surface (in situ),mechanical,acetic,survey of museum collection
Reason for describing collection:taxonomic analysis
Collectors:Savage Collection dates:1970s
Collection method comments: BRSUG, University of Bristol Geology Museum, Bristol, England, United Kingdom
The specimen was prepared using a combination of acid and mechanical methods. Each block was repeatedly submerged in dilute acetic acid (7.5%) and consolidated with dilute paraloid in acetone between treatments (for further details see Lindsay 1987). Breakages were repaired using a concentrated solution of paraloid in acetone. A hand-held pneumatic engraver was used to remove matrix from localised areas of coarser sediment that proved more resistant to the acid treatment. Wherever possible, acid was used to expose new areas of bone in order to avoid the risk of accidental drill contact.
Metadata
Also known as:Lyme Regis
Database number:138246
Authorizer:R. Benson Enterer:R. Benson
Modifier:M. Carrano Research group:vertebrate
Created:2013-01-08 01:48:30 Last modified:2013-07-31 11:21:41
Access level:the public Released:2013-01-08 01:48:30
Creative Commons license:CC BY
Reference information

Primary reference:
44197. P. J. Hopley. 2000. A new plesiosauroid specimen from the Sinemurian, Lower Jurassic, of southern England. Proceedings of the Dorset Archaeological and Natural History Society 122:129-138 [R. Benson/R. Benson]