A revision of the trionychid turtle Procyclanorbis sardus Portis, 1901 from the late Miocene of Sardinia (Italy)

Procyclanorbis sardus Portis, 1901 is the first fossil trionychid turtle described from Sardinia. This late Miocene taxon was originally considered to have affinities with the African and southern Asian cyclanorbines. We here redescribe in detail the holotype specimen of this species, which has suffered severe degradation since its original publication. A comparison between the original state of the fossil and its current state of preservation is provided. On the basis of its anatomy, affinities of Procyclanorbis sardus with cyclanorbines are discarded and this taxon is demonstrated to be an indeterminate pan-trionychine. The distribution of fossil trionychids in the Mediterranean Islands is also discussed.