Today, whilst I was baking bread, I spent some time looking at my trilobite collection. I have a good selection of specimens from around the UK, but my drawers that hold the Carboniferous age specimens are not very full.
The reality is simply that in the UK, Carboniferous trilobites are uncommon. They tend to be small species that are found at a few localities and in many cases, the fossils are the same colour as the rock matrix, so they do not stand out.
This is a specimen from Derbyshire, not far from Castleton. It is the pygidium (Tail segment) of a species called Griffithides and it is about 1cm across its width.
Similar specimens from French sites are much more distinct, being fossilised in a different material to the surrounding rock matrix. They stand out clearly and are easily found, making them more common in collections and museums.
The picture on the right is of a specimen of Griffithides from The Humbolt Museum of Natural History. It clearly shows the form of this type of trilobite. The tail segment is large compared to the overall size of the specimen and the three lobes of the tail tend to be fused into a solid plate with the ridges of the segments standing out.
These Proetid trilobites were from a time when the trilobites were in decline. Only a few families are found worldwide and they were mainly fast swimming coastal species with well developed compound eyes. They are well adapted for avoiding predation, and in the Carboniferous, there were a lot of things about that would eat trilobites.