I find trilobites just fascinating, not least that they did not become extinct as such but evolved over hundreds of millions of years – they are actually from the same family as wood lice !  Albeit wood lice are much smaller than most trilobites – but they do go back to ‘grass roots’, as it were, enjoying damp places like their ancestors who actually inhabited then emerged from the seas.


Heinrich Harder 1906 Die Gartenlaube

One of the most numerous and successful marine organisms of the early Paleozoic (approx. 450 million years ago) in the Cambrian period, Trilobites flourished for nearly 300 million years. They ranged in size from a few millimeters to 90cms (about 3 feet).


Most Trilobites lived in shallow ocean waters and on reefs. Trilobite tracks show a wide variety of activities and some of the spiny Trilobites may have been capable of swimming. More than 1500 species are known and many more yet to be described.


Trilobite Sections


The name is derived from the three lobes into which the body segment is divided, the head (Cephalon), thorax and posterior section or Pygidium (tail). They had many legs each with a set of gills and most had sophisticated multi-faceted eyes.


Like most arthropods they could only grow by shedding their old skins and many fossils are actually the shed external skeletons.


Trilobite Plaque

Their skeletons are found in all types of sedimentary rocks from limestones to shales.


Sites where they have been found include the Atlas Mountains, Morocco, parts of Northwest Scotland, Illinois USA, Utah & Virginia USA, Oklahoma, and British Columbia.


Fossilised Trilobite


The legs of the Trilobite were softer than the exoskeleton and as such did not tend to preserve as well although there have been a few specimens that showed legs and some antennae also in Burgess Shale in Canada and Chengjiang in China.



Trilobites are very obviously similar in shape to living forms such as the wood lice but they are both actually from the same family as arachnids (spiders) and crustaceans (shrimps, lobsters, crayfish etc.) – they are all Arthropods.

Trilobite Fossil


The featured image shows a very fine detailed example particularly the head detail and it is from the Atlas Mountain range in Morocco.