This study is devoted to the radiolarian biostratigraphy of Middle-Upper Jurassic pelagic siliceous successions in the Southern Alps and in Western Sicily (Italy). The crucial complement to this research is the occurrence of ammonites in the studied successions as well as in the under- and overlying formations. The close occurrence of ammonites and well preserved radiolarians is generally quite rare: the investigated sections allow the radiolarian zones to be well calibrated by ammonites zones.
The study of siliceous successions in the Southern Alps and in Western Sicily benefits from the fact that they are approximately coeval and may be referred to analogous paleogeographical contexts. These similarities enable us to compare radiolarian assemblages of different geographical areas and to correlate different Tethyan paleogeographical domains. The age of the studied successions ranges from the Bathonian to the Kimmeridgian. 
The paleogeographical domains are two pelagic plateaux (Trento Plateau in the Southern Alps and Trapanese Domain in Western Sicily) and one basin (Sicano Domain in Western Sicily).The abundance of radiolarians in the selected successions enable us to study them for a twofold purpose: to date directly most of the sections (whose age was generally based on the ages of the bracketing formations), and to improve the calibration of radiolarian zones thanks to the occurrence of ammonites. Six stratigraphic sections have been studied for radiolarians for the first time: Cava Vianini (Southern Alps), Fornazzo Strada, Fornazzo Cava, Castello Inici, Balata di Baida, Favignana Island (Northwestern Sicily). For other three sections (Coston delle Vette and Ceniga in the Southern Alps, and Sant’Anna in Southwestern Sicily) the previous radiolarian data have been increased improving the biochronological precision. The radiolarian preservation is moderate and similar in all the sections; some samples of Cava Vianini, Coston delle Vette and Sant’Anna show a very good preservation.
The biostratigraphical analysis of  this research has been made using the Unitary Association method. The occurrences of 100 selected taxa from 9 stratigraphic sections have been computed using software BioGraph, which recognized 20 Unitary Associations (UAs). By evaluating the lateral reproducibility and the taxa assemblages of each UA I grouped the 20 UAs into 6  biostratigraphic units (UAZ-SA A to F: Unitary Associations Zones for Sicily and Southern Alps). The radiolarian biozones UAZ-SA A to F show a good reproducibility throughout all investigated sections: This fact makes the correlation of the sections possible. The combined occurrence of both radiolarians and ammonites provided a new Bathonian to Late Kimmeridgian radiolarian zonation for the Southern Alps and Western Sicily. 
Thanks to this new zonation, the ranges of Eucyrtidiellum unumaense (Yao) s.l. and Williriedellum (?) marcucciae Cortese have been extended with respect to those stated in the literature. 
The new zonation based on UAZ-SA A to F is a regional syntheses that will be used both to improve the zonation of the INTERRAD Jurassic-Cretaceous Working Group, and to create a database for the definition of new radiolarian zones for the Jurassic Mediterranean Tethys.