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 (similar to 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 similar to 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, changes in 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.

Automated summary

Paludotona is an insular lagomorph genus that existed from approximately 8.3 to 6.7 million years ago. It is considered a living fossil and thrived as a ghost lineage in an insular refugium for at least 14 million years. Paludotona acquired a much larger body size compared to its continental ancestors, possibly due to synecological factors, lower mortality rate, changes in the insular palaeobioprovince, and successive climate changes.