La subfamilia Ataxioceratinae (Ammonoidea) en el Oxfordiense Superior de la Provincia Submediterránea: origen y evolución

Abstract

The subfamily Ataxioceratinae Buckman arises at the turn of the Middle-Upper Oxfordian (Upper Jurassic) in the South-European Platform, spreading mostly throughout the Submediterranean province during Upper Oxfordian-Lower Kimmeridgian times. The genus Orthosphinctes Schimdiwoíf, type-species Ammonites tizianí Omt, is the first genus of this family and is first recorded al the Bifurcatus-Bimammatum Zone boundary in most of the West-Tethys areas. The successive forms of this genus appear fairly well-represented all across the Iberian Range (E Spain), allowing the recognition of many Orthosphinctes biohorizons within the classical biosiratigraphic scheme for the Upper Oxfordian in the Submeditarranean Province. The origin of the genus Subnebrodites at the base of the Planula Zone is proposed from the main Orthosphinctes stem via the 'intermediate', synthetic form O. fontannessi (Chofpaj)