Centralomys benericettii ( De Giuli, 1989 )

Colombero, Simone, Pavia, Giulio & Carnevale, Giorgio, 2014, Messinian rodents from Moncucco Torinese, NW Italy: palaeobiodiversity and biochronology, Geodiversitas 36 (3), pp. 421-475 : 436-439

Centralomys benericettii ( De Giuli, 1989) ( Fig. 4 M-R)

Castillomys (Centralomys) benericettii De Giuli, 1989: 204 , pl. 3, figs 1-10.

Centralomys benericettii – Martín-Suárez & Mein 1991: 68, pl. 2, figs 12-17. — Abbazzi et al. 2008: 622, fig. 6E, F. — Colombero et al. 2013: 113, fig. 4D-F, M-O.

Castillomys sp. – Cavallo et al. 1993: 17, fig. 8A.

Centralomys cf. benericettii – Angelone et al. 2011: 98, fig. 14.

TYPE LOCALITY. — Brisighella 1, Italy.

OCCURRENCE IN THE STUDIED LAYERS. — MCC3, MCC4, MCC5, MCC7.

REFERRED MATERIAL. — One maxillary fragment bearing M1 and M2; one mandibular fragment bearing m1 and m2; 31 isolated M1; 26 isolated M2; four isolated M3; 35 isolated m1; 31 isolated m2; three isolated m3.

MEASUREMENTS. — Table 4.

DESCRIPTION

M1

t3-t6-t9 are aligned forming a straight labial margin; t1 bis always present; t1 connected to t5; the t3 exhibits a posterior spur reaching the base of t 5 in about 45% of the specimens; t4-t5-t6-t9-t8 form a stephanodont crest with low (or absent) t4-t8 connection; t12 strongly reduced.

M2

t1 bis always present, the t1 exhibits a posterior spur that reaches the base of t 5 in 65% of the specimens; t3 smaller than t1; t4-t5-t6-t9-t8 form a stephanodont crest with low (or absent) t4-t8 connection; t12 absent or very reduced; three or four (10%) roots

M3

Large t1; t3 absent; t4-t8 connection low, t6-t8 connection rare and low.

m1

A tiny tma is present in 30% of the specimens, a longitudinal spur connects the hypoconid-entoconid complex and the protoconid-metaconid complex in 33% of the specimens; posterior heel poorly developed; the labial cingulum departs from the c1 and reaches the anteroconid without contacting the protoconid.

m2

A longitudinal spur connects the hypoconid-entoconid complex with the protoconid-metaconid complex in 35% of the specimens; c1 small; it can merge with the hypoconid; labial cingulum low without accessory cusplets.

m3

Anterolabial cuspid formed by a slight swelling of the enamel; the posterior complex exhibits a very compressed and transversely elongated shape; it is slightly shifted on the lingual side

REMARKS

The studied material belongs to a small stephanodont murid and is assigned to the genus Centralomys . As a matter of fact, the stephanodonty, the tendency to develop longitudinal connections between the tubercles of the molars ( Schaub 1938), is not as well developed as in Castillomys Michaux, 1969 , a genus that usually displays more developed longitudinal crests. Besides, the genus Centralomys differs also from Occitanomys Michaux, 1969 , in which the longitudinal connections are less developed. Moreover, the presence of well-developed t1bis and t1-t5 connection in the M1 supports the ascription of the studied material to Centralomys . The measurements of Centralomys from MCC are nearly identical to those of Centralomys benericettii from the latest Miocene localities of Verduno (Colombero et al. 2013) and Brisighella 25 (Martín-Suárez& Mein 1991). Direct comparison of the material from MCC with that from Brisighella 1 (type locality), Brisighella 25 ( De Giuli 1989), and Verduno (Colombero et al. 2013) revealed a very similar morphology especially in the t3-t5 connections in the upper molars (which are generally absent and, when present, are low) and in the poorly developed longitudinal spurs in the lower molars, thereby justifying the assignment to the species Centralomys benericettii . Moreover, the material from MCC is characterized by M2 always bearing a t1 bis and, like in the assemblages from Brisighella and Verduno, the 30% of the available m1 exhibit a tiny tma. However, it should be noted that specimens with slightly more pronounced stephanodonty are more frequent at Brisighella 25 and Verduno than in MCC (Colombero et al. 2013). As far as concerns Verduno and MCC, such differences might be related to different palaeoecological conditions (Colombero et al. 2013; Colombero & Pavia 2013).

According to some authors (García-Alix et al. 2008b; Hordijk & de Bruijn 2009), C. benericettii should be placed within the genus Occitanomys . In particular, García-Alix et al. (2008b) considered C. benericettii as a junior synonym of Occitanomys alcalai Adrover, Mein & Moissenet, 1988 , a species present in the latest Miocene and Early Pliocene deposits of Spain,arguing that there is no morphological difference between these two forms. Actually, the measurements of O. alcalai are slightly larger than those of C. benericettii from Moncucco ( Adrover et al. 1988; 1993a; García-Alix et al. 2008b; Minwer-Barakat et al. 2009a, b), as they only partially overlap. From a morphological point of view, in the M1 of O. alcalai the posterior spur of the t3 never reaches the t5 whereas in C. benericettii from MCC the contact is feeble but present in 45% of the M1. Other differences can be detected in the position of the t 1 in the M1 that is more anteriorly placed in O. alcalai , in the less developed longitudinal spurs of the m1, in the lower frequency of the tma in the m1 and in the rarity of the t1bis in the M 2 in O. alcalai . Moreover, in our opinion Centralomys cannot be considered a synonym of Occitanomys differing in particular in the presence of more developed longitudinal connections in both upper and lower molars.

Castillomys magnus Sen, 1977 from the Pliocene of Çalta (see Sen 1977) was ascribed to the genus Centralomys by Martín-Suárez & Mein (1991) mainly due to the presence of four roots (see Hordijk & de Bruijn 2009). In a successive paper, Sen (1998) confirmed the attribution of this species to the genus Centralomys pointing out the presence of four roots in the M2, weak longitudinal spurs in the lower molars and larger dimensions than Castillomys . Centralomys magnus differs from the studied material mainly in the larger average dimensions, even if the size ranges partially overlap, and in the presence of more developed longitudinal connections in the upper molars.

We compared the specimens of C.benericettii from MCC with Castillomys gracilis van de Weerd, 1976 , known in Spain between the Late Miocene and the Pliocene. This species is smaller than C. benericettii ( van de Weerd 1976; García-Alix et al. 2008b) except for the population from La Gloria 4 ( Adrover et al. 1993a) whose range overlaps with that of MCC. Morphologically, C. gracilis mainly differs in the most developed stephanodont crest in the upper molars, and in the absence or very rare occurrence of the t1bis in the M2. In addition, the tma is usually absent in the m1 of C. gracilis , being only sketched in a single specimen from Calicasas-4b (García-Alix et al. 2008b), the longitudinal spurs are more developed and the labial cingula are weaker.

The record of C. benericettii is therefore restricted to the latest Messinian of Italy. Unfortunately, the very sparse record of continental vertebrates in the Italian Peninsula during the Miocene does not allow to define the evolutionary history of this taxon. Nonetheless, its occurrence in other localities such

as Verduno (Colombero et al. 2013), Ciabót-Cagna ( Cavallo et al. 1993), Borro Strolla ( Abbazzi et al. 2008) and Brisighella ( De Giuli 1989), indicates the existence of geographical connections between the northern and central parts of the Italian Peninsula, at least during the post-evaporitic phase of the MSC.

Figures

FIG. 4. — Isolated teeth of Paraethomys Petter, 1968, Occitanomys Michaux,1969, Centralomys De Giuli,1989 and Micromys Dehne, 1841 from Moncucco Torinese. A-F, Paraethomys meini (Michaux, 1969); A, MGPT-PU128032, M1 dex.; B, MGPT-PU128040, M2 sin.; C, MGPT-PU127602, M3 sin.; D, MGPT-PU127146, m1 sin.; E, MGPT-PU127302, m2 sin.; F, MGPT-PU127603, m3 sin.; G-L, Occitanomys brailloni Michaux, 1969; G, MGPT-PU127062, M1 sin.; H, MGPT-PU127447, M2 dex.; I, MGPT-PU127657, M3 dex.;J, MGPT- MGPTPU127166,m1 dex.; K, MGPT-PU127305,m2 dex.; L, MGPT-PU127658,m3 sin.;M-R, Centralomys benericettii (De Giuli, 1989); M, MGPT-PU128090, M1 sin.; N, MGPT-PU128278, M2 sin.; O, MGPT-PU128115, M3 sin.; P, MGPT-PU128272, m1 sin.; Q, MGPT-PU128321, m2 sin.; R, MGPT-PU128144, m3 dex.; S-V, Micromys bendai van de Weerd, 1979; S, MGPT-PU127434, M1 dex.; T, MGPT-PU127251, M2 dex.; U, MGPT-PU127600, m1 dex.; V, MGPT-PU127601, m2 sin. Scale bar: 1 mm.