While on a trip to Cow gap 19Sep 2013 (Beachy head) I spotted this in the Gault clay.
The pictures do not do it justice. its very hard and appears to be hollow at the wider end (Neck?)
the other end tapers off to a point (tail?)
Fantasic fossil and that alone made the 3 hour round trip plus the soaking in the rain worth it.
Best regards Pete
The guys over at ukfossils think its a Rastellum (gregareum) ?
Just googled Rastellum (gregareum?) and found quiet of few pictures that are identical to my little specimen.
Thank you and best regards Pete
I can see the resemblance with the rhynchonella vespertillio.
Still have trouble getting my head around a 155 million year old fossil being in my hand and that no one has seen until I cleaned the sediment from it!!!
Off to Barton on sea tomorrow with my 10 year old son, should be a good day out.
thanks for the link.
Ended up in west malling down, which was not my cup of tea so moved on to Birling gap and found a nice Echinoid - Echinocorys.
But going back to the Rastellum can you tell me what its made of ? Ive spent some time prepping it and have taken better pictures which show more detail
Good job. That's come up very nicely!
In general, living sea shell -type creatures usually have their hard parts made of calcium carbonate, or, much less commonly, calcium phosphate. Calcium carbonate occurs in two forms in these invertebrates: aragonite and calcite. Aragonite becomes less stable as temperature and pressure increase, and since those changes commonly occur during lithification of sediment, agagonite in invertebrate shells alters to a more stable form (calcite) as fossilization occurs. Thus, calcite is a common mineral in fossils, and although aragonate occurs as well, it becomes more unusual in older fossils. During fossilization further changes may occur, such that calcite and/or aragonite and/or calcium phosphate get replaced with silica, haematite, pyrite or other minerals. Sometimes, the original mineral is dissolved and not replaced, leaving a cavity. That can result in fossils existing just as molds, or as casts - where such molds become filled with other material.
Oyster shells are made of calcite, and that's probably still what your fossil Rastellum is composed of.
Do you know, I have no idea what actual geology books are available today, let alone which ones to recommend!
However, it is interesting that you mention the NHM's 'British palaeozoic fossils', because I still have my copy of that (plus the Cenozoic and Mesozoic sister publications) from Uni.
From the same era in my past, I still rate HMSO's 'British Regional Geology' series, eg.
You can pick these up cheaply secondhand.
Like I say, I really don't know how these compare with modern books on the subject, but I personally still think they're useful.