Origin, phylogeny, faunal composition, and stratigraphical significance of the Albian engonoceratidae (pulchelliaceae, ammonitina) of Peru

Recent study of the Albian ammonite fauna from Peru provides a major revision of the systematic position and taxonomy of the family Engonoceratidae, which we place in the superfamily Pulchelliaceae. We consider the oldest south Tethyan representatives, specifically the mahmoudii species described in Algeria, ancestors of the Andean taxa. Peruvian specimens show a monophyletic evolution marked by four morphological and stratigraphical stages, from unornamented Platiknemiceras to evolute Glottoceras and Engonoceras. The weakly ornamented Parengonoceras haasi, a late lower Albian index species, is considered the ancestor of all Peruvian engonoceratids. The family reaches its highest diversity (15 species) in the upper part of the Lower Albian. The genus Glottoceras, which comprises the majority of the microconchs, is considered an Andean paraphyletic equivalent to the Tethyan genus Knemiceras. Globally, Peruvian engonoceratids are dominated by representatives of the genera Parengonoceras and Glottoceras. We also report several engonoceratids, including Engonoceras and Platiknemiceras, for the first time from Peru.