Description
Trilobites are a group of extinct marine arthropods, similar to modern-day crabs. They lived from the Cambrian period, 521 million years ago, to the Permian period, 250 million years ago. They were some of the first animals on Earth and also among the most successful, living continuously for 270 million years until their extinction in the Permian. They ranged in size from 1 to 72 cm in length, depending on the species.
Trilobites were covered by a chitinous exoskeleton that provided protection, divided into 3 lobes (right, left, and axial), which is where their name originates (tri-lobed). The body consisted of a head (cephalon), a segmented thorax, and a pygidium, the tail end of the exoskeleton. The exoskeleton was shed periodically through the process of molting: as the animal grew, it left behind the old exoskeleton and formed a new one. Most trilobite fossils consist of this mineralized exoskeleton left behind after molting and preserved in sedimentary rocks. Soft parts (antennae and legs) are rarely found.
They were among the first animals to possess eyes! Their compound eyes, similar to those of insects, contained numerous lenses formed from their own exoskeleton, which have been preserved in today's fossils and are highly appreciated by collectors. However, some deep-sea trilobites were blind.
During the Devonian period, trilobites began a long arms race, equipping themselves with spines to protect against predators. This led to the emergence of extremely spectacular exoskeletons, which have been preserved in fossilized form to this day in the rocks of Morocco and are highly sought after by collectors worldwide.
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