Butseloglis tenuis ( Bahlo, 1975 )

Lu, Xiaoyu, Costeur, Loïc, Hugueney, Marguerite & Maridet, Olivier, 2021, New data on early Oligocene dormice (Rodentia, Gliridae) from southern Europe: phylogeny and diversification of the family, Journal of Systematic Palaeontology 19 (3), pp. 169-189 : 172-174

Butseloglis tenuis ( Bahlo, 1975)

( Fig. 3A–H)

1971 Gliravus aff. majori ; Hugueney et al.: 2432.

Type locality. Heimersheim, Germany, MP24.

Holotype. HLMD /Hhm 409, right M2.

Specimens and measurements from St-Martin-de-Castillon C. UCBL-FSL_218048 to 218055 and 218070, for measurements see Table 1 and Supplemental material, Appendix 2 ( Fig. 3A–H).

Description of the specimens from St-Martin-de-Castillon C. The occlusal surface of P4 is strongly concave and cusps are well developed. The paracone is slightly higher than the protocone. The anteroloph and posteroloph are weak and shorter than other lophs. The protoloph is straight and as developed as the metaloph. A weak precentroloph is the only centroloph in the ‘V’- shaped trigone; it is interrupted and connects to the paracone. All tropes are absent.

M1/M2. The pattern is as simple as P4 but with a trapezoid shape. The occlusal surface of M1 is usually more concave than M2. The cusps are strong. The anteroloph is longer than the posteroloph in M2, and both of them are straight and as high and developed as the other lophs in upper molars. The protoloph and metaloph are slightly bent anteriorly in their middle. A weak unique centroloph is present; it either connects usually to the paracone (precentroloph) or more rarely to the metacone (postcentroloph).

M3. Only one M3 has been found; it is smaller than M1 and M2 and about the size of P4. The shape is more triangular than other teeth but the pattern is otherwise similar to M1 and M2. Although the anteroloph and protoloph are transverse, the metaloph extends substantially posterolabially with a bend which results in the metacone being located more lingually than the paracone. The precentroloph is free labially. The posteroloph is oblique (instead of transverse in M1 and M2) due to the reduction of the posterolingual side of the tooth.

p4. The tooth is strongly concave on the lingual side. The metaconid is the highest cuspid. The entoconid and hypoconid are distinct and connected to each other by a well-developed and rounded posterolophid. Comparatively other lophids are weak. The anterolophid and the mesolophid are very weakly developed. The metalophid connects to both the metaconid and protoconid. There is no connection between the mesolophid and the entoconid. No tropid is observed between the main lophids.

m1/m2. They are trapezoidal in shape but m2 is slightly wider in the anterior part. All main cuspids are distinct and lophids are transverse and parallel. The posterior arm of the metaconid and the mesolophid do not join. The anterolophid is very weak and disconnected from the protoconid. The metalophid extends from the protoconid but does not connect to the metaconid. In the unique m1, the short and weak centrolophid is located anterolingually to the mesolophid and is free. However, in m2s, the centrolophid and all tropids are absent. The posterolophid only connects to the base of the entoconid.

m3. The unique m3 is smaller than m2, with a rounded posterior border. Its pattern is the same as other lower molars; however, the lophids seem more robust. The centrolophid is difficult to observe (either weakly developed or poorly preserved), but it seems to connect to the posterior arm of the metaconid. There is a deep groove between the posterolophid and the entoconid.

Remarks. Butseloglis tenuis was initially described under the genus Gliravus Stehlin & Schaub, 1951 , then referred to genus Schizogliravus Freudenthal, 2004 , which is now a junior synonym of genus Butseloglis ( Vianey-Liaud 2003) . The material of Gliravus tenuis in Vianey-Liaud (1994) from Montalb́an S was later referred to B. montisalbani ( Freudenthal 2004) . Likewise, B. montisalbani is also present in MLB1D but not B. tenuis (Freudenthal & Mart́ın-Súarez 2007a). The size of B. tenuis is indeed similar to that of B. montisalbani but its dental pattern is simpler than both B. montisalbani and Butseloglis hispanicus van Dam, 1998 : the posterotropid is absent, and only one centroloph is present in upper molars. Here we report for the first time the occurrence of this species in SMC (MP24).