First 185 words of the document:
Trilobites are extinct marine arthropods.
They appeared in large numbers during the Lower Cambrian.
Trilobites reached their maximum development in the Middle Ordovician.
Still common in the Silurian, they gradually declined towards the end of the
They were rare during the Carboniferous and became extinct in the Permian.
Trilobites were probably benthonic, living on the bottoms of shallow seas. The
evidence for this is various types of trace fossil that include crawling, burrowing,
ploughing and resting marks. Some trilobites may have been swimmers.
The exoskeleton enclosed and supported the soft body and was periodically moulted
as the trilobite grew. Most trilobites had prominent eyes which were compound like
modernday insect eyes.
Generally Trilobites were small creatures ranging between 5 and 8 cm in length but
some have been found up to 70 cm.
Add a scale and the following labels to the trilobite below: Cephalon (head)
How many thoracic segments does this trilobite have?