1. Introduction The Iberian Trough comprised the northern, central and south-eastern regions of the Iberian Subplate that were temporally or permanently flooded by the Protoatlantic Ocean or by the Tethys Sea during the late Cenoman- ian-early Turonian. It was bordered on the west by the Hesperian Massif and on the east by the Ebro Massif, and was broadly related to the North Cantabrian, Basque, Pyrenean and Levantine basins. Palaeogeo- graphically, the Iberian Trough, also named “Iberian Basin”, was divided into different domains. These were, from the north to the southeast, the Outer Navar- ro-Cantabrian Platform, and the Inner Castilian Plat- form, where the cephalopods presented here have been collected. During intervals of relatively high sea level the Iberian Trough extended from the Inner Castilian Platform to the southeast along the Levantine Platform, from which it received directly Tethyan influence. The Inner Castilian Platform, also known as “Castilian Plat- form”, “North-Castilian Platform” and “Cameros- Castilian Zone”, was divided into the North-Castilian Sector and the Central Sector. The North-Castilian Sec- tor included the North-Ebro Area and the South-Ebro Area, and the Central Sector comprised the La Deman- da Area and the Guadarrama Area (Fig. 1). The Outer Navarro-Cantabrian Platform corre- sponded to a distal open marine environment that pro- Newsletters on Stratigraphy © Gebrüder Borntraeger 2009 Vol. 43/2: 139–164, March 2009 Ammonite zonation of the upper Cenomanian and lower Turonian in the Iberian Trough, Spain Fernando Barroso-Barcenilla 1, 2 , Antonio Goy 1 and Manuel Segura 2 With 10 figures Abstract. New ammonite successions from the upper Cenomanian and lower Turonian of the Iberian Trough are studied and compared with the assemblages obtained by other authors. As a result, the upper Cenomanian Eucalycoceras rowei, Calycoceras (Calycoceras) naviculare, Neolobites vibrayeanus, Metoic- oceras mosbyense, Metoicoceras geslinianum, Vascoceras gamai and Spathites (Jeanrogericeras) subcon- ciliatus, and the lower Turonian Choffaticeras (Choffaticeras) quaasi, Spathites (Ingridella) malladae, Chof- faticeras (Leoniceras) luciae, Mammites nodosoides and Wrightoceras munieri biostratigraphic divisions are identified, defined and discussed, and representative specimens of their index species are illustrated. Key words. Ammonoidea, Biostratigraphy, Upper Cenomanian, Lower Turonian, Iberian Trough, Spain. DOI: 10.1127/0078-0421/2009/0043-0139 0078-0421/09/0043-0139 $ 6.50 © 2009 Gebrüder Borntraeger, D-14129 Berlin · D-70176 Stuttgart Authorsʼ addresses: 1 Departamento y UEI de Paleontología, Facultad de Ciencias Geológicas e Instituto de Geología Económica, Universidad Complutense de Madrid-CSIC, 28040 Madrid, España – Spain. 2 Departamento de Geología. Edificio de Ciencias. Universidad de Alcalá de Henares. 28871 Alcalá de Henares, España – Spain. Corresponding author: F. Barroso-Barcenilla, fbarroso@geo.ucm.es