Simplomys, García-Paredes & Peláez-Campomanes & Álvarez-Sierra, 2009

García-Paredes, Israel, Peláez-Campomanes, Pablo & Álvarez-Sierra, M. Ángeles, 2009, Gliridae (Rodentia, Mammalia) with a simple dental pattern: a new genus and new species from the European Early and Middle Miocene, Zoological Journal of the Linnean Society 157 (3), pp. 622-652 : 637-640

REMARKS ON SIMPLOMYS SIMPLICIDENS

Simplomys simplicidens was proposed by De Bruijn (1966) for glirid material with a rather simple dental pattern from Miocene localities of the Calatayud– Montalbán basin. This author named an assemblage Ps. ibericus if more than 75% out of at least ten M1-2 had the ‘ ibericus – morphotype’ and Ps. simplicidens if more than 75% of at least ten M1-2 had the ‘ simplicidens – morphotype’. If one of the two patterns did not exceed 75% of the total number of M1-2 or if the assemblage consisted of fewer than ten specimens, the indication Ps. ibericus – simplicidens was used ( De Bruijn, 1967). According to De Bruijn & Moltzer (1974) it was not clear whether the specimens with ‘ ibericus ’ morphology and those with ‘ simplicidens ’ morphology were morphotypes occurring in one natural population, or represented two species. In fact, there are several specimens belonging to S. simplicidens amongst Ps. ibericus paratypes, such as paratype number 60–422, figured in plate IV, figure 7 in De Bruijn (1967).

Daams (1974) studied Pseudodryomys material from ten Miocene localities of Spain, analysing the distribution of standard morphotypes of the cheek teeth. The results show that Ps. ibericus and Ps. simplicidens are separated species and the original diagnoses were emended. Later field campaigns, mainly in the Aragonian and Ramblian type areas (Calatayud–Montalbán basin), have increased the number of localities with Pseudodryomys and Simplomys gen. nov. enormously (see Supporting Information Appendix S1).

Based on more than 2700 specimens from 59 localities of the type area of the Aragonian, García-Paredes (2006) demonstrated trends toward size increase of the cheek teeth ( Fig. 10 ), toward simplification of the p4 and toward simplification of the posterior part in the m3 of S. simplicidens . This study also demonstrated that morphological features, such as simplification degree of the m3, can be used to distinguish S. simplicidens from S. robustus , even though size ranges of S. simplicidens and S. robustus overlap ( Fig. 10 ).

S. julii S. simplicidens S. meulenorum sp. nov. S. robustus

However, when these species occur in the same locality, S. robustus is always larger than S. simplicidens .

Given these new insights, the material from several middle Aragonian localities in the area of Madrid ( Spain), described as Pseudodryomys robustus ( Alberdi et al., 1980, 1981, 1984, 1985; Sesé et al., 1985; López Martínez et al., 1987; Herráez, 1993; Cerdeño & Íñigo, 1997), could be revised. The measurements of this material fit within the size ranges of Simplomys simplicidens from biochronologically similar localities in the Calatayud–Montalbán basin ( Fig. 10 ). Furthermore, the m3 from Madrid show the same degree of simplification as S. simplicidens ( Fig. 4H ). As a consequence, the Ps. robustus assemblages from middle Aragonian localities of Madrid (Moratines; Estación Imperial; Paseo de las Acacias; O’Donnell; Henares 2; Arroyo del Olivar) are now assigned to S. simplicidens . This change in the specific determination was already suggested by Amezua et al. (2000), Peláez-Campomanes & Herráez (2000), Soria et al. (2000) and Peláez-Campomanes et al. (2003), without, however, justification or mention of the previous specific status of the aforementioned material.

The situation with the material from Middle Miocene locality Armantes 3 in the Calatayud– Montalbán basin described as Pseudodryomys cf. simplicidens by De Bruijn (1967) and assigned to Pseudodryomys robustus by Daams (1974) and Daams et al. (1977) is similar and is here assigned to Simplomys simplicidens .

Pseudodryomys meini Adrover, 1978 described from Navarrete del Río (local biozone Z, MN1, Lower Miocene) was considered a junior synonym of Ps. simplicidens by Agustí (1983) as well as by Daams & de Bruijn (1995). However, these authors did not give any argument to justify this decision. The morphology of the specimens described as Ps. meini fits the diagnosis of Simplomys simplicidens . Adrover (1978) noted that the Navarrete del Río material is smaller than the type material of Pseudodryomys [= Simplomnys] simplicidens . Because of the trend toward size increase in S. simplicidens , this species is smaller in older than younger localities ( Fig. 10 ). Therefore, Ps. meini Adrover (1978) is considered a subjective synonym of S. simplicidens .

Simplomys simplicidens has been reported from localities of Portugal (e.g. Antunes & Mein, 1986), France (e.g. Baudelot & Collier, 1982; Aguilar, Escarguel & Michaux, 1999), Germany (e.g. Mayr, 1979; Wu, 1990, 1993), and Switzerland (e.g. Kälin, 1997) (see Supporting Information Appendix S1 for details on localities and references).

The material from the Lower and Middle Miocene fissure fillings in southern France listed by Aguilar et al. (1999) is of special interest. Several of these localities (Ste. Catherine 3, Ste. Catherine 4, Ste. Catherine 5, and Ste. Catherine 9) contain both S. simplicidens and S. robustus . As a result of the nature of these fossil sites, the material assigned to S. simplicidens and to S. robustus in Aguilar et al. (1999), may represent the same species at different stages of evolution ( Fig. 10 ). Therefore, further analysis is needed in order to establish whether this material belongs to S. robustus , S. simplicidens , or to Simplomys meulenorum sp. nov.

Figures

Figure 4. Simplomys simplicidens (De Bruijn, 1966) from Valdemoros 3F (Fig. 4A–H) and Artesilla (Fig. 4I–P) (collection MNCN). A, P4 VA3F-27. B, M1 VA3F-39. C, M2 VA3F-52. D, M3 VA3F-62. E, p4 VA3F-342. F, m1 VA3F-73. G, m2 VA3F-76. H, m3 VA3F-95. I, P4 ART-1134. J, M1 ART-931. K, M2 ART-943. L, M3 ART-1173. M, p4 ART-2455. N, m1 ART-966. O, m2 ART-990. P, m3 ART-1186. Right side specimens underlined.

Figure 10. Temporal distribution of average surface of the upper and lower cheek teeth in species of Simplomys gen. nov. from the Aragonian type area (Calatayud–Montalbán basin, Spain). Only localities with at least five measurable specimens of each element are included. Horizontal bars represent two times the standard deviation. Modified after García-Paredes, 2006.