THE FORGOTTEN ICHTHYOSAUR: REVALUATION OF THE FIRST OPHTHALMOSAURID SPECIMEN FROM THE UPPER JURASSIC OF THE MARCHE APENNINES (CENTRAL ITALY)

With the exception of the Triassic material of Monte San Giorgio, which is quite abundant and well-preserved, the Italian fossil record about ichthyosaurs for the remainder of the Mesozoic is very poor, and usually consists of few disarticulated elements. Lower Cretaceous remains have been described from the Northern Apennines, south of Modena and Bologna; another rostrum belonging to Platypterygius sp. has been recently reported from the Lessini Mts., near Verona; and a few vertebrae are reported from the Triassic of Sicily. In the summer of 1976, an ichthyosaur specimen was discovered in the locality of Camponocecchio, near Genga (Ancona, Marche, Italy) in an Upper Jurassic outcrop of the Marche Apennines. The specimen consists of a reasonably complete skeleton crushed on a slab, with a disarticulated skull, partially articulated vertebral column (from the atlas-axis to the tail bend, with few missing vertebrae), part of the pectoral girdles and some elements of the forelimbs. During the Late Jurassic, the Umbria-Marche area was occupied by a pelagic domain consisting of numerous structural highs and lows, as a result of the fragmentation and drowning of the pre-rifting Early Jurassic carbonate platform. The Genga ichthyosaur comes from the Calcari ad aptici e Saccocoma Formation (sensu Galluzzo & Santantonio, 2002), and thanks to the combination of the occurrence/lack of some micro- and macrofossils with biostratigraphic meaning, it has been possible to date the ichthyosaur-bearing level to the late Kimmeridgian – earliest Tithonian. The history of the Genga ichthyosaur has always been problematic, mainly because of the lack of attention that the authorities turn to paleontological findings: it took more than 20 years before the specimen could find a proper location, where it was finally prepared and where it is still exposed, in the Abbey of San Vittore di Genga. Since its discovery, few studies have focused on the Genga ichthyosaur (e. g. Fastelli & Nicosia, 1980; De Marinis & Nicosia, 2000), but never addressing its taxonomy and paleogeographical importance. This is the first time that this Mesozoic marine reptile is described and compared with other Late Jurassic and Early Cretaceous ichthyosaurs by including it in the most recent phylogenetic analysis of ophthalmosaurids.