My Collection #2

Small Kosmoceras jason on a piece of Oxford Clay with a tiny
belemnite to the left.

These fossils were collected from Must Farm Brick Pit in Whittlesey, near Peterborough in Cambridgeshire, UK in June 2016.

Kosmoceras ammonites are known from Callovian age Oxford Clays of the Late Jurassic Period in Europe. These ammonites therefore date back to around 163 Ma. As with these two fossils, they are commonly found flattened in the clay, rarely it is possible to find three dimensional casts of the shell. The maximum diameter known from fossils is about ten centimetres. There is evidence of sexual dimorphism in these ammonite, the more decorated males have a smaller shell than the females, the purpose of the ornamentation is unknown.

Calcitic Kosmoceras jason from Kings
Dyke Brick Pit.

A larger iridescent Kosmoceras jason on a piece of Oxford Clay

The preserved phragmocone of a belemnite from the
Oxford Clay.

Cylindroteuthis is a belemnite known from the Early Jurassic, ~200 Ma, to the Early Cretaceous, ~140 Ma. This specimen is rather common, being found in Asia, Europe, North America and New Zealand. The calcitic guard of the belemnite is what is commonly found, lengths range from ten centimetres to twenty-two centimetres. Rarer fossils exhibit traces of appendages and an ink sac, showing their relation to squids. The guard would be an internal feature as traces of blood vessels have been found on the surface of the guard. This fossil is not to be confused with the shell of the belemnite, this is found within the guard, as shown in the photo to the right.

The largest of the Cylindroteuthis belemnites in my collection from the Oxford Clay at Kings Dyke Brick Pit.

This is a fragment on a bone from the giant fish Leedsichthys. This member of the pachycormidae is known from Callovian sediments of the late Jurassic. Discovered by Alfred Leeds in 1889 when the Peterborough brick making industry was taking off and quarries were being opened in and around the city, Leeds collected various marine fossils from the Oxford Clay in this time. Fossils have been found in England, France, Germany and Chile. In 2002, another individual was discovered in the Must Farm pit in Whittlesey by students at Portsmouth University. An excavation led by Jeff Liston of Yunnan University, revealed thousands of delicate bones, including the pectoral fin. A lot of the skeleton would have been composed of cartilage and so it doesn't fossilise. Size estimates put the fish at around twelve metres long. It is believed that a spike in planktonic populations were the reason behind the size of the Leedsichthys. Being a filter feeder, water would have been forced through gill rakers that removed the plankton from the water.

A small fragment of Leedsichthys problematicus from the Oxford Clay at Kings Dyke Brick Pit.

The larger and more complete Gryphaea
in my collection.

Also known as the Devil's Toenail, Gryphaea is an extinct genera of bivalve mollusc. Their geological range is from the late Triassic through to the Eocene. These bivalves are some of the more common finds in Jurassic marine deposits of Europe. They possibly lived in small colonies as shown in the photograph to the right. The bivalve had a larger hooked valve and a smaller, flatter lid. The
larger valve would be embedded in the sediment whilst the lid remained exposed. It is one of the only bivalves that have one valve larger than the other.

A broken Gryphaea from the Oxford Clay.

The underside of the above Gryphaea.