The body mass of Paludotona (Lagomorpha, Mammalia): first approach to the ecology of the last stem lagomorph (Tusco-Sardinia palaeobioprovince, Late Miocene)

Paludotona, an insular lagomorph genus endemic of the Tusco-Sardinia palaeobioprovince (~8.3-6.7 Ma), is the last representative of the heterogeneous basal group of early lagomorphs. It post-dates the last appearance datum of stem lagomorphs to 6.7 Ma, i.e., by 2.5 my with respect to the previous datum. This makes Paludotona, during the Late Miocene, a living fossil thriving in an insular refugium. We have a record of only the last 15% or less of the temporal distribution range of Paludotona: in fact Paludotona developed in isolation sensu lato as a ghost lineage for at least 14 my. Paludotona matched the pattern followed by small mammals in insular environments, acquiring a gigantic size with respect to continental ancestors. Its body mass (BM) is here estimated in ~1100 g, i.e., three to five times the BM of the taxa here taken as reference for European MP28-MN1 stem lagomorphs, the group from which Paludotona likely stemmed. The reasons for such an enormous BM increase are multiple and interconnected: synecological factors s.l., lower extrinsic mortality, changesin size and degree/pattern of fragmentation of the area of the insular palaeobioprovince, and successive climate changes (which caused a rapid evolutionary pulse followed by a relative stasis following the pattern of Mein’s biphasic model). At any rate, through BM estimation and morphological observation we discuss some biological traits of Paludotona: there is evidence of increased lifespan (though, at present, not quantitatively determined), and we suspect a change in posture and locomotion caused by the noticeable BM increase.