TECNOCYRTINA REDUX: TIMING AND PATTERNS OF ALLOPATRIC SPECIATION AND PHYLETIC TRANSITIONS IN A LINEAGE OF CYRTINID BRACHIOPODS IN THE MIDDLE-UPPER DEVONIAN OF NORTH AMERICA

New data on species sequences in western Canada and published data on all other known North America species of the genus Tecnocyrtina Johnson and Norris permit identification of the probable locus of its endemic center from which it subsequently expanded its paleogeographic range into the Great Basin and central and eastern North American carbonate platforms in the late Givetian and early Frasnian. The geographic and temporal distribution patterns of elements of two species groups permit reconstruction of its evolutionary history during the Middle and Upper Devonian in tropical carbonate platforms of western and central North America.

The oldest Tecnocyrtina occurs in inner platform deposits of the Flume Formation in eastern British Columbia, and suggest that the Cyrtina-Tecnocyrtina transition occurred in shallow coastal embayments along the Peace River Arch during the initial sea level rise of Devonian eustatic T-R cycle IIa of Johnson and others (Taghanic Event 1). Elements of the missouriensis group then expanded their range into the epeiric carbonate platform of central Canada during the late Givetian hermanni Zone transgression (Taghanic Event 2). The most significant migration and geographic speciation event within the missouriensis group occurred during the Upper disparilis Zone transgression (Taghanic Event 3) evidenced by occurrences of five species and subspecies in late Givetian platforms in western and central and eastern North America. The oldest species of the billingsi group evolved in outer shelf environments the Great Basin from T. m. teleta in the late Givetian. Widespread emergence of carbonate platforms led to extinction of all western North American species of the missouriensis group in the late Givetian, with the last species persisting into the very late Givetian and early Frasnian (Upper Devonian) in Iowa.