Glirulus lissiensis Hugueney & Mein, 1965 (Fig. 7A, B)

Glirulus lissiensis Hugueney & Mein, 1965: 117, figs 57- 63. — Daxner-Höck & Höck 2009: 419, fig.17 (cum syn.).

TYPE LOCALITY. — Lissieu, France.

Occurrence in the studied layers. — MCC5; MCC7.

Referred material: — Two isolated M2; a single isolat- ed m1.

Measurements. — M2: MGPT-PU 127496 (1.05 × 1.03); MGPT-PU 127510 (0.98 × 0.93); m1: MGPT-PU 128351 (0.96 × 0.95).

DESCRIPTION

M2

Five main and four accessory ridges; well-developed endoloph connected with all main ridges; slightly convex anteroloph; protoloph and anterior centroloph connected on the labial side; metaloph and posteroloph connected on the labial side; posterior centroloph elongate and weakly connected to the metaloph; three main roots plus a small rootlet partially fused with the antero-labial root.

m1

Five main and five accessory ridges; endolophid connected with all main ridges and narrowed between mesolophid and centrolophid; two accessory ridges between anterolophid and metalophid, the posterior one being very small; centrolophid not reaching the labial border; mesolophid long, strongly forward bent and weakly connected to the endolophid and to a small anterior accessory ridge on the lingual side; labial side of posterolophid strongly curved forward reaching the level of the lingual end of the mesolophid; two roots.

REMARKS

The small glirid recovered at MCC can be distinguished from the Miocene genus Paraglirulus Engesser, 1972 based on the absence of a free labial end on the anterior centroloph of the upper molars and of the presence of a complete endolophid in the m1 (van der Meulen & de Bruijn 1982). These features indicate that the material from MCC belongs to the genus Glirulus Thomas, 1906, distributed in Europe since the Early Miocene and currently represented by the small Japanese dormouse Glirulus japonicus (Schinz, 1845).

The comparison with the material of Glirulus lissiensis Hugueney & Mein, 1965 from its type locality Lissieu did not reveal substantial morphological differences with the specimens from MCC. Moreover, the single m1 recognized in MCC is very similar to the holotype of G. lissiensis since both display a very similar structure of the endolophid that narrows between mesolophid and centrolophid, five accessory ridges, the first two lying between anterolophid and metalophid, and mesolophid and posterolophid strongly bent forward.

The size of the material from MCC is consistent with that of G. lissiensis from Lissieu (Hugueney & Mein 1965) and other Miocene European localities such as Oberdorf (de Bruijn 1998), Rudabanya (Daxner-Höck 2005), Eichkogels (Daxner-Höck & de Bruijn 1981), Belchatów (Kowalski 1997), Richaldholf, Schernham, and Kohfidish (Daxner- Höck & Höck 2009) except for one of the two available M2 (MPST-PU127496), which is slightly larger. The size of this latter specimen, however, fits well with those of G. aff. lissiensis from Saint Bauzile (Mein & Romaggi 1991). The material from MCC is also roughly similar in morphology and size to Glirulus pusillus (Heller, 1936) from some Pliocene and Pleistocene European localities (Kowalski 1963; Michaux 1970; Fejfar & Storch 1990; Daoud 1993; Mörs et al. 1998; Dahlmann 2001; van den Hoek Ostende 2003). According to Hugueney & Mein (1965), G. lissiensis differs from G. pusillus in having a less-developed endolophid, shorter labial branches of the main ridges in the lower molars and biradiculated lower molars. However, the number of roots in lower molars does not seem to be a reliable feature to distinguish these two species since lower molars of G. pusillus from Gundersheim 4 (Fejfar & Storch 1990) and many other localities (Daoud 1993; van den Hoek Ostende 2003) are biradiculated. The specimens of Glirulus from MCC are assigned to G. lissiensis since they are morphologically nearly indistinguishable from those of the type population from Lissieu. G. lissiensis is currently considered as the descendant of the Lower Miocene Glirulus diremptus (Mayr, 1979) (Daxner-Höck & de Bruijn 1981; van der Meulen & de Bruijn 1982; Nadachowski & Daoud 1994). According to Daxner-Höck & Höck (2009) its biochronological range extends from MN4 to MN13. The Plio-Pleistocene G. pusillus possibly derived from G. lissiensis (Daxner-Höck & de Bruijn 1981; van der Meulen & de Bruijn 1982; Nadachowski & Daoud 1994). The extant G. japonicus, a taxon endemic of the Japanese Archipelago, shows a dental pattern very similar to that of the extinct European species, also displaying slightly larger sizes and lower molars with three roots (van der Meulen & de Bruijn 1982; Mein & Romaggi 1991); this taxon has been classically interpreted as the descendant of Villanyan immigrant populations of G. pusillus from Europe (van der Meulen & de Bruijn 1982).

An exceptionally preserved specimen of G. aff. lissiensis was found at Saint-Bauzile (MN11) (Mein & Romaggi 1991). The extraordinary preservation of soft tissues revealed the presence of a patagium suggesting an adaptation to gliding, a locomotor behavior not observed in extant glirids.