Mimomys savini, HINTON, 1910

Masini, Federico, Maul, Lutz C., Abbazzi, Laura, Petruso, Daria & Savorelli, Andrea, 2020, Independent Water Vole (Mimomys Savini, Arvicola: Rodentia, Mammalia) Lineages In Italy And Central Europe, Fossil Imprint 76 (1), pp. 59-83 : 62

Mimomys savini

Mimomys savini is known only from Palaearctic Biharian sites. The Biharian biochronological unit is based on the co-occurrence of the genera Microtus and Mimomys ; it therefore extends from the first occurrence of Microtus (represented by Allophaiomys, which includes primitive members of the genus Microtus ) to the disappearance of Mimomys (represented by M. savini ) ( Fejfar et al. 1998). Allophaiomys and M. savini appear roughly at the same time in Eurasia, around 2 Ma.

In Europe, and more specifically in Italy, M. savini characterises both the early Biharian (defined by the cooccurrence of M. savini and M. pusillus and correlated with the Calabrian Age, early Early Pleistocene) and the late Biharian (time interval when M. savini was not associated with M. pusillus ), which corresponds approximately to the first part of the early Middle Pleistocene. Readers are kindly referred to Gliozzi et al. (1997), Sala and Masini (2007) and Masini and Sala (2007) for correlations between Fejfar et al.’s (1998) standard biochronological scale based on small mammals and Azzaroli’s (1977) Italian Mammal Ages, on the one hand, and the International Chronostratigraphic Scale, on the other.

Mimomys savini is first recorded in Italy based on a few remains from the localities Le Strette and Bosco Chiesa Nuova, in Upper Valdarno, where also large mammal remains of the Tasso Faunal Unit were found ( Bosco 1898, 1899, Torre 1985, Sala and Masini 2007). These Lower Pleistocene deposits are magnetostratigraphically correlated with the base of the Calabrian Stage and biochronologically with the early part of the early Biharian; they therefore date to around 1.6–1.8 Ma ( Torre et al. 1996, Azzaroli 1998, Masini and Sala 2007, Sala and Masini 2007, Rook and Martínez-Navarro 2010). Breda and Marchetti (2007) correlated the M. cf. savini bearing levels of Leffe ( Stehlin 1930, Masini et al. 1996) with the transition between the Early Pleistocene Tasso and Farneta Faunal units and therefore with the early Biharian. Scoppito (L’Aquila Basin) is yet another early Biharian site that yielded Mimomys savini ( Masini et al. 1996, Kotsakis et al. 2003). A younger age is assumed for the fossiliferous site of Soave/ Cava Sud ( Mimomys cf. savini ) ( Pasa 1947, Bartolomei 1980, Masini and Santini 1991), and further Italian early Biharian sites with M. savini are Monte Peglia ( Van der Meulen 1973, Masini et al. 1998), and Castagnone/Pontrestura I (Northern Monferrato, Piedmont, NW Italy) ( Siori and Sala 2007). In the latter site fossils come from both the basal levels of the local sedimentary succession (1 st Alluvial Unit, fluviatile deposits and soils) and from the Alluvial Unit, at the (pedogenetic) top of the sequence. At least the basal levels are late Early Pleistocene (late early Biharian) in age because M. savini co-occurs with evolved representatives of Microtus (Allophaiomys) cf. nutiensis, Mimomys pusillus , and Ungaromys cf. nanus ( Giraudi et al. 2003, Sala and Masini 2007, Siori and Sala 2007). The fossil bearing stratigraphical sequence yielded a positive magnetization referred to the Jaramillo by Giraudi et al. (2003).

Late Biharian faunas with M. savini were found at Soave/ Monte Tenda ( Bon et al. 1991, Masini et al. 1996), and Slivia ( Ambrosetti et al. 1979, Bon et al. 1991, Gliozzi et al. 1997). Scant, late Biharian remains of M. savini , somewhat more recent than the specimens from Soave/Monte Tenda, also come from Rifreddo in Sant’Arcangelo Basin (Basilicata), which yielded Microtus (Terricola) arvalidens , Microtus (Iberomys) ex gr. huescarensis -brecciensis, Macroneomys cf. brachygnathus and which show normal magnetisation of the early part of the Brunhes magnetochron ( Fanfani 2000, Masini et al. 2000, 2005).