DURANGITES, PROTACANTHODISCUS (AMMONITINA) AND SOME RELATED FORMS OF UPPER TITHONIAN-BERRIASIAN AGE IN THE MEDITERRANEAN TETHYS (SE FRANCE,SPAIN, ALGERIA AND TUNISIA)

The relationships between Durangites and Protacanthoduscus are revised using also calpionellids ages. The earliest Durangites in the calpion ellids A2 and A3 (pars) subzones are both microconchs and macroconchs. In the A3 subzone, microconchs are differentiated only at species lev el, while macroconchs change into Protacanthodiscus type which is in p art the macroconch of Durangites. Durangites and Protacanthodiscus are Mediterranean Tethyan taxa from which originated the Tethyan afflux d uring A2 subzone (France, Tunisia) and, at the same time (according to the ammonites), the Durangites of Mexico where the genus was first de scribed and considered for a long time as endemic. Another line of Dur angites develops Dalmasiceras-like forms. ((C) Academie des sciences/ Elsevier, Paris.).