Paleoenvironments

The paleoenvironments that resulted in the Ottawa area varied with time. At some points in history it was dry land inhabited by land organisms. At other times, it was covered with Epeiric seas and only marine organisms could survive. Then there was the glacial period in which most of Canada was covered with glaciers and few organisms survived. The organisms at the time of the Cambrian/Ordovician transgressions had several life modes. There were infauna and epifauna; which are terms for organisms living in the sea floor or on the sea floor respectively. Within the epifauna there were vagile or moving creatures and sessile or motionless creatures. There were benthic organisms or bottom dwellers, planktic organisms or floaters, and nectic organisms or swimmers.

Painting by Michael Léveiller

There were also different feeding mechanisms from species to species. Some were autotrophic and made their own food by photosynthesis. Others were heterotrophic and ate other organisms. Within the heterotrophes, there were suspension feeders which filtered the water or deposit feeders which ate food found on sea floor. There were two different skeleton types. Endoskeletons or internal skeletal structures and exoskeletons or external skeletal structures. There were five different skeletal compositions. There were organic, biomineralized, calcite/aragonite, calcium phosphate and silica type skeletal compositions. There were also four different types of skeletal growth. Accretion occurred when new material was added, addition occurred when a new unit was grown, molting occurred when the old exoskeleton was removed and a new one grown, and modifiable was when growth occurred within the skeleton as in the organisms tissues. Two of the organisms that survived in the Ottawa environment during the Ordovician included trilobites and brachiopods.

The organisms that can be found in the Ottawa area include trilobita, brachiopoda, cephalopoda, pelecypoda, porifera, and anthozoa.

Two of these groups of organisms will be discussed in more detail: trilobites and brachiopods.