The skull of Stephanorhinus kirchbergensis (Jäger, 1839) (Mammalia, Rhinocerotidae) from Spinadesco (Cremona, Lombardia, Northern Italy): morphological analyses and taxonomical remarks – an opportunity for revising the three other skulls from the Po Valle

• The new S. kirchbergensis is an opportunity for revising other fossils of Po valley.
• The exceptional preservation show new distinctive characters to classify the species.
• The discovery improves the knowledge of the Pleistocenic rhinoceroses of Europe.

The exceptional discovery of a complete and extraordinary well-preserved skull of Stephanorhinus kirchbergensis (Jäger, 1839) on an alluvial bar of the Po river near Spinadesco (Cremona, Lombardia, Northern Italy) in July 2013 presented us with the opportunity for reporting on the specimen. The thorough morphometric and morphological analyses carried out on the specimen (dentition included) revealed typical characteristics of S kirchbergensis – also known as “Merck's rhinoceros”. These peculiar tracts highlighted distinctive taxonomic characteristics which are useful for reassessing the classifications of the specimens found in adjacent areas up to now.In this paper, the distinguishing characters are discussed privileging the morphological features rather than the metrical characteristics also if the dimensions of the skull are significative. The adopted criteria, employed for the first time by Loose (1975), were used also for comparing the skull from Spinadesco with other fossil rhinoceros skulls discovered in the Po Valley adjacent areas: the Dicerorhinus hemitoechus falconeri ( Azzaroli, 1962) from Mezzana Rabattone (Zinasco, Pavia), the Dicerorhinus hemitoechus aretinus ( Azzaroli, 1962) from San Colombano al Lambro (Milano), and the Dicerorhinus hemitoechus intermedius from the Torrente Stirone studied by Cigala-Fulgosi (1976).Up to now, S. kirchbergensis appears to be a rather rare species on the vast Eurasian landmass as few fossils have been found in a relatively limited number of localities. Furthermore, there are generally not available chrono- or biostratigraphic data.