Centralomys benericettii (De Giuli, 1989) (Mammalia, Rodentia): a latest Messinian murid from Northern and Central Italy. New data from Piedmont

New remains of the small-sized stephanodont murid Centralomys benericettii (De Giuli, 1989), a Late Miocene form exclusively found in Italy, were recently collected in the post-evaporitic deposits of the Tertiary Piedmont Basin (Piedmont, NW Italy) in two new localities of latest Messinian age: Moncucco Torinese and Verduno. These data considerably enlarge the knowledge of this species, formerly documented only by the late Messinian record from Monticino gypsum quarry (Brisighella, Emilia Romagna, Central Italy) and from very sparse remains from Borro Strolla (Tuscany, Central Italy) and Ciabòt Cagna (Piedmont, Northern Italy) at the Mio-Pliocene limit. The recently recovered remains of C. benericettii from Piedmont are described herein in order to better define the spectrum of variation of this poorly known form. The morphological differences between the populations of C. benericettii from Moncucco Torinese and Verduno can be related to palaeoenvironmental differences, even if further evidence is required to confirm this hypothesis. RIASSUNTO [Centralomys benericettii (De Giuli, 1989) (Mammalia, Rodentia): un muride del Messiniano terminale dell’Italia centrosettentrionale. Nuovi dati dal Piemonte] Nuovi resti fossili di Centralomys benericettii (De Giuli, 1989), un piccolo muride stefanodonte che rappresenta una forma italiana del Miocene terminale, sono stati recentemente rinvenuti nei depositi messiniani post-evaporitici del Bacino Terziario Piemontese (Piemonte, Italia) nelle due località di Moncucco Torinese (AT) e Verduno (CN). Questi dati ampliano notevolmente la conoscenza di questa specie, fin qui documentata solamente dal record di età Messiniano terminale proveniente dalla cava di gesso di Monticino (Brisighella, RA, Emilia Romagna, Italia centrale) e da alcuni rarissimi resti provenienti da Borro Strolla (SI, Toscana, Italia centrale) e Ciabòt Cagna (CN, Piemonte, Italia settentrionale) al limite Miocene-Pliocene. In questo lavoro vengono descritti i resti fossili di C. benericettii rinvenuti recentemente nelle località piemontesi in modo da evidenziare lo spettro di variazione di questa forma così poco conosciuta. Le differenze morfologiche che si riscontrano tra le popolazioni di Moncucco Torinese e Verduno potrebbero essere messe in relazione a differenti condizioni paleo-ambientali. Bollettino della Società Paleontologica Italiana, 52 (1), 2013 28 Moncucco Torinese The site of Moncucco Torinese is located in a gypsum quarry in the northern sector of the TPB. The Messinian succession of this area is quite disturbed by sinsedimentary tectonic and diapiric processes, resulting in the in-situ dismemberment and consequent resedimentation of the pre-evaporitic (S. Agata Fossili Marls) and evaporitic (PLG) deposits during the subsequent phase that led to the formation of the Valle Versa chaotic complex (VVC) in the “MSC acme” (Dela Pierre et al., 2007). This complex succession was afterwards sealed, during the postevaporitic phase of the MSC, by the fresh and brackish water sediments of the Conglomerati di Cassano Spinola Formation. The unit is then overlain by the Zanclean marine marly clays of the Argille Azzurre Formation. The Sphaeroidinellopsis acme interval (5.30-5.21 Ma) is recognized slightly above the base of the Pliocene succession, thus corroborating the correlation to the MPl1 Zone (Violanti et al., 2011). Vertebrate fossils were recovered together with fresh and brackish molluscs and ostracods in the Conglomerati di Cassano Spinola Formation (Angelone et al., 2011). During the excavation campaign, nine levels were recognized in a 3 m-thick succession. Layers 3, 4, 5 and 7 of Angelone et al. (2011) contain vertebrate fossil remains. The ostracod assemblage recovered in layer 1 is correlated with the Loxocorniculina djafarovi Zone (Angelone et al., 2011) thus constraining the deposition of the investigated succession in the second post-evaporitic phase of the MSC between 5.40 and 5.33 Ma (CIESM, 2008; Grossi et al., 2011). Moreover, the taxonomical composition and the relative abundances of rodent taxa are very similar in each of the fossiliferous layers of Moncucco Torinese (Colombero, 2012). Therefore, we can suppose that the deposition of the studied succession occurred in a short time-lapse, at least less than 80 Ky, during the post evaporitic phase of the MSC under approximately unvarying palaeoecological conditions. The occurrence of Prolagus sorbinii Masini, 1989 and Centralomys benericettii indicates that the vertebrate assemblage can be referred to the MN13 unit (latest Messinian) (Angelone et al., 2011). Verduno The site of Verduno is located on the left bank of the Tanaro River, in the southern sector of the TPB. The studied layers belong to the Pollenzo section, one of the most complete Messinian sections composing the Alba succession (Bernardi et al., 2010; Dela Pierre et al., 2011). The pre-evaporitic marls and euxinic shales of the topmost S. Agata Fossili Marls represent the base of the Messinian succession. The PLG, composed by alternated gypsum and shale beds, overlie the S. Agata Fossili Marls and record the terminal part of the evaporitic interval. The MSC acme is marked by an erosive surface on which slumped mudstones are present. The post-evaporitic phase is recorded by an 80-100 m thick succession of muddy, silty and gravelly beds that characterize the continental and brackish deposits of the Conglomerati di Cassano Spinola Formation. The succession is closed by the Pliocene marine sediments of the Argille Azzurre Formation. Because of the presence of the nannofossil species Reticulofenestra zancleana Di Stefano & Sturiale, 2010 the lowermost consisting of different gypsum lithofacies alternated with euxinic shales. This unit roughly corresponds to the evaporitic interval of the MSC and was deposited between 5.96 Ma and 5.60 Ma (CIESM, 2008). The ciclicity observed in the alternation of gypsum and shale beds is believed to have been controlled by climatic changes linked to the Earth’s precession (Krijgsman et al., 1999). The second stage of the MSC, also known as “MSC acme” (5.60-5.55 Ma), corresponds to a sea-level drop occurring at the Mediterranean scale, caused by the strong reduction in the Atlantic connections that in some areas led to the erosion of the PLG with the formation of the Messinian Erosional Surface (MES) and the resedimentation of the erosive products (CIESM, 2008; Dela Pierre et al., 2011). The uppermost portion of the Messinian succession of the TPB consists of freshand brackish-water sediments of the Conglomerati di Cassano Spinola Formation. This unit was deposited during the post-evaporitic phase of the MSC (5.55-5.33 Ma) (CIESM, 2008; Dela Pierre et al., 2011) a period that recorded the so-called Lago Mare events (CIESM, 2008). The TBP succession is then closed by the Zanclean deposits of the Argille Azzurre Formation that consist of marine shales and marls (Dela Pierre et al., 2007; Rossi et al., 2009; Mosca et al., 2010).