An Asaphid trilobite that is very common in the Cobourg Fm. and found in almost all strata above the base of the Gull River Fm. This trilobite could be quite large: specimens found at Colborne, Ontario, show Isotelus latus could grow to at least 18 inches. Isotelus maximus in the younger Cincinnatian (equiavalent to the Georgian Bay Fm in Central Ontario, the Russell Fm in the Ottawa area and the Nicolet Fm. in Quebec) could reach similar sizes. Isotelus rex, found in Ordovician rocks near Churchill, Manitoba, is the largest complete trilobite ever found.
Isotelus platycephalus, Gull River Fm.
Isotelus (undescribed, similar to Isotelus iowensis), Ottawa
Multiple specimen from same strata as above trilobite
\
8″ dorsal specimen from same strata. Note the forked hypostome (mouth plate)
Isotelus ottawensis, near Picton, Ontario
Isotelus gigas, Port Hope, Ontario
Isotelus gigas, near Picton, Ontario
