The Pliensbachian ammonite Dayiceras dayiceroides and Early Jurassic paleogeography

Abstract

Uptonia? dayiceroides Mouterde is placed in the genus Dayiceras and its age established as latest Jamesoni Zone to possibly earliest Domerian. The species is abundant and associated with faunas of Tethyan aspect along the northeastern Pacific margin. First occurrences in Oregon and Nevada and new occurrences in British Columbia are reported. Localities at apparently high paleolatitudes are attributed to post-early Pliensbachian transcurrent fault displacements. Genetic continuity with a disjunct population in Portugal is postulated via a central Atlantic seaway, here named the Hispanic Corridor, connecting the eastern Pacific and western Tethys Oceans. The existence of this corridor during the Pliensbachian is supported by several lines of independent paleobiogeographic evidence.