MIDDLE CAMBRIAN (DRUMIAN) SOLENOPLEURID TRILOBITES FROM THE AVALON TERRANE, NEW BRUNSWICK AND NEWFOUNDLAND, CANADA

The Avalon terrane is the remnant of a microcontinent that accreted to the margin of Laurentian North America in the Silurian after first docking with Baltica. Split by the opening of the modern Atlantic, the Avalon terrane is now represented by Cambrian and Ordovician faunas and sedimentary rocks in eastern Canada and the northeastern United States, as well as England and Wales. Although Avalonian trilobites played a major role in reconstruction of the Cambrian Iapetus Ocean, they have been the subjects of surprisingly little modern systematic work. Solenopleurids are diverse and abundant components of Middle Cambrian (Drumian Stage) trilobite faunas of the Manuals River Formation in both New Brunswick and Newfoundland. Unlike Avalonian Britain, where the trilobites are typically preserved in shale, the faunas of the Manuels River Formation occur commonly in carbonate nodules, and have suffered little post-depositional compaction. At least five species represent the genera Solenopleura, Parasolenopleura and “Jincella”, and they facilitate correlation with Drumian successions in Avalonian Britain and southern Sweden (Baltica). Early ontogenetic stages possess a fixigenal tubercle array that is conserved in holaspids, demonstrating that Family Solenopleuridae are among the oldest members of Order Aulacopleurida.