Please browse more of our Fossils & Crystals. 381-391 Million years old, Atlas Mountains, Morocco. Fully prepared on original matrix.Nicely laid out on matrix making a very displayable piece. Fossil size 63mm x 32mm. Excellent detailed ribs, head, eyes. Trilobites (meaning three lobes) are a well-known fossil group of extinct marine arthropods that form the Trilobita. The earliest trilobites known from the fossil records are dated to some 520 to 540 million years ago. Trilobites led a more complex existence compared to Ammonites, they had legs and crawled on the shallow sea bed, they swam into greater marine depths and they even left the sea in order to walk on the surface of the earth. Their bodies were also more complex than Ammonites, the fossilisation process varies a lot more and good fossils are often rarer and more expensive than Ammonites. The photographs show the exact Trilobite that you will receive. We despatch immediately but we have no control over the speed of deliveries.