Ordovician Canada

Lunataspis is the oldest known xiphosuran, with three known species all dating from the late Ordovician (latest Sandbian for L. borealis, Katian for L. gundersoni, earliest Hirnantian for L. aurora).

genus of trilobites

Didymograptus is an extinct genus of graptolites with four rows of cups. They lived during the Middle Ordovician, to Late Ordovician.

event of around 467 million years ago

Tetragraptus is an extinct genus of graptolites from the Ordovician period.