The early Silurian pentamerid brachiopodCostistricklandia canadensis(Billings, 1859) and its biostratigraphic and paleobiogeographic significance

Abstract

Costistricklandiais a common, easily recognizable pentamerid brachiopod in upper Llandovery to lowest Wenlock rocks of eastern Laurentia, Avalonia and Baltica. In this paper, the poorly knownCostistricklandia canadensis(Billings) is re-described from the upper Telychian Rockway Dolomite of the Niagara Escarpment, Ontario. Compared to the relatively complete record of theStricklandia-Costistricklandiaevolution in the Welsh Borderland and the Baltic region, true representatives of theStricklandia lenslineage are sporadic in North America, including those from the Merrimack Formation of Anticosti Island, the Red Mountain Formation of Alabama, the Hopkinton Formation of Iowa, and the Nonda Formation of the northern Rocky Mountains. Although the exact mode of speciation in theStricklandia-Costistricklandiaand thePentamerus-Pentameroidestransitions remains debatable, the common association ofCostistricklandiaandPentameroidesmake them a useful concurrent biozone for correlating middle to upper Telychian rocks of North America and Europe. Paleobiogeographically, thePentameroides-CostistricklandiaFauna marks the third major pulse of pentamerid faunal migration between Laurentia and its adjacent paleo-plates during the Early Silurian, following the limited intercontinental dispersal of the early LlandoveryVirgianaFauna and the quasi-cosmopolitan dispersal of the middle LlandoveryPentamerusFauna.