Trilobites are extinct arthropods from the Palaeozoic Era, that lived in prehistoric oceans between 540 to 245 million years ago. Their closest living relative is the horseshoe crab.

Bryozoans are colonies made from many individual microscopic animals that are common in the seas both today and in the past.

Trilobites are the earliest arthropods and are the first known fossils with eyes. Their hard outside skeleton, or exoskeleton, is divided into 3 lobes lengthways - hence the name.

Trilobites can also be divided into 3 parts widthways; a head (cephalon) often with eyes, the body (thorax) consisting of articulated segments, and a tail (pygidium). Their legs, which are rarely preserved, lay underneath. Many trilobites were capable of rolling up in a ball, probably for protection. Like all arthropods the hard outer skeleton meant that trilobites periodically moulted in order to grow bigger.

The two trilobites shown here are from a famous British fossil locality, the Much Wenlock Limestone Formation, Dudley in the West Midlands. They are beautifully preserved in limestone. Over 400 million years ago they were part of a diverse reef community, living in warm, shallow seas. The first is Dalmanites myops and the second is Calymene blumenbachii, both lived about 425 million years ago.

The Dalmanites specimen is actually a montage of two specimens of the same species; although all the parts are genuine a tail from another individual has been attached to the head and body. Such composites are not uncommon from the Dudley area.

The final specimen is a distinctive Carboniferous bryozoan, Archimedes, named after the water pump invented by the Greek philosopher. The screw-shaped central column once supported a intricate net of individual. The colony stood upright on the sea floor and probably generated feeding currents from top to bottom, spiralling these downwards like a helter-skelter.

Copyright (c) 1996 The Natural History Museum