Trilobites

Trilobites



The class Trilobita belongs to the phylum Arthropoda. The distinguishing features of arthropods are an exoskeleton of chitin which is sometimes calcified, a segmented body and jointed appendages. Trilobites molted to conform exoskeleton to new bodysize with growth. Only the dorsal part of the exoskeleton calcified so that is what fossils of trilobites represent. Trilobites were benthic, epifaunal and vagile creatures. They moved in the water column just above the sea floor. They were deposit feeders.(Thompson 1997)

The warm, shallow, sunny waters of the early Paleozoic were favorable for the development of trilobites at the end of the Precambrian and explosion at the beginning of the Cambrian. By late Cambrian and early Ordovician, the trilobites were declining since many other creatures had developed and were infilling the niche once occupied by trilobites and a few other creatures.

In Ottawa, Isotelus and Flexicalymene species of trilobites have been found.


This is an Isotelus sp. from the Hull Formation, Québec.
from the private collection of Andrew Dalby.