An exhibition of fossils collected by George Rae and bequeathed to the Hunterian Museum
11th September - 20th December 2003
Trilobites are extinct sea creatures that came in a huge variety of shapes and sizes. Successful for an era of over 300 million years, the niches that they once filled are now occupied by fish, shrimps and crabs. Over 15,000 species have been described, with more every year. These hard-shelled arthropods are the prized specimens of many fossil collections.
As with the dinosaurs, there are many theories as to why the trilobites died out. They may have been out-competed by fish or other marine animals, suffered from climate change or from variations in sea level. Researchers in the United States suggested that they had trouble moulting properly. However, trilobites did not all die out at once and it is likely that more than one of these reasons is responsible for their demise 248 million years ago. Of the sixty-three families that existed towards the end of the Cambrian period, only forty-two survived the Ordovician period and nineteen through the Silurian, with only three in the Permian period before the age of the trilobites ended completely.
Some species of trilobite grew into strange shapes to protect themselves, catch prey or to see better. Some could roll into a ball for protection, like woodlice (slaters) do today. The spines on some would certainly deter any predators.
Many trilobites had eyes similar to those of insects today. Some were made of minute lenses that covered most of the head, while some had their eyes on stalks. Some trilobites were completely blind, although they could sense their surroundings using other devices similar to radar. Trilobites were extremely well adapted to their environment, which is why they survived for so long but, ironically, this finely-tuned adaptation may have helped to cause their extinction, as they would not have been able to cope with change.
Measurements are of the fossil not the field of view unless otherwise stated