Fossil Finder Database 2022

Bivalve xenomorph of ammonite

An ammonite on an oyster? In very muddy seas, oysters need a hard surface to attach to when they start life, otherwise they are simply smothered by the mud. In the Oxford Clay sea, dead ammonites lying on the sea bed provided a good starting point. As the oyster grew, it made an exact copy…

Brachiopod shell

A first This shell (collected in 1983) is similar to specimens identified for the first time by Thomas Davidson in 1852. This is the first example of Trigonosemus found in south-west English chalk.

Bivalve shell

Good eating? This bivalve, Modiolus, is very similar to the modern-day mussel. Like today’s mussels, they probably formed colonies, often partly burying themselves in mud, and filtering the water for food. They in turn would have been food for crabs and starfish. As the name suggests, bivalves consist of two shells. ‘Bi’ means two and…

Snail shell

Here is a superb block of Portland Limestone known as the Roach and containing the high spired snail Aptyxiella portlandica, the ‘Portland screw’, another type of snail and the bivalve shells of Myophorella. The insides of the shells have been filled with sediment to produce internal casts. The gaps are holes where the shells has been dissolved. The Roach…

Bivalve shells and ammonite

Ammonite sandwich! Ostrea oysters, which are types of bivalves, can fix themselves to hard substrates and grow upon these. In this instance, two oysters attached themselves to either side of a dead ammonite’s shell, and almost encompassed it. Perhaps the seafloor was too soft for them to attach to.

Bivalve shell

There are Myophorella clavellata and Gervillia bivales on this block. Notice how all of the shells are lying in the same orientation. This suggests that a strong current was flowing across the sea bed when these animals became buried. Convex shells tend to flip over with the curved face uppermost as this is a more stable angle than the…