Trilobites (Phylum: Arthropoda, Class: Trilobita)
24Introduction:
Trilobites were amongst the earliest arthropods. They were widely distributed in the prehistoric oceans until the emergence of fish and other advanced animals, which led to their decline. There were nine main orders of trilobites. Given their numerous types and diverse forms, they have been called the butterflies of the prehistoric oceans.
The trilobite body is generally broad and flat, and made up of three sections: head, thorax, and pygidium. There are several pairs of legs, which have breathing gills on them. As suggested by the name, the segmented dorsal shell is divided into three longitudinal lobes by two grooves.
When disturbed or confronted by an enemy, the trilobite would curl up so that the head and pygidium would meet, exposing only the hard shell, thus protecting the vulnerable abdomen.