Simplomys meulenorum, 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 : 642-644

SIMPLOMYS MEULENORUM GARCÍA- PAREDES

SP. NOV. ( FIG. 8 )

Synonymy Pseudodryomys robustus in Díaz Molina & López

Martínez, 1979. Pseudodryomys robustus in Alférez et al., 1982. Pseudodryomys robustus in Álvarez Sierra et al.,

1994. Pseudodryomys robustus in Alférez et al., 1999. Pseudodryomys robustus in Morales et al., 1999.

Pseudodryomys robustus pro-parte in Van Dam et al., 2006.

Pseudodryomys robustus pro-parte in Van der Meulen et al., 2005.

Pseudodryomys robustus pro-parte in Van der Meulen & Peláez-Campomanes, 2007 .

Diagnosis: Medium to large-sized Simplomys with simple dental pattern. Centrolophs are absent. The anteroloph is interrupted in the middle in half of the M1 and may be connected medially to the protoloph. The centrolophid is absent or poorly developed and does not extend into the central valley. The mesolophid of the m3 is reduced and limited to the lingual part (entoconid). In most cases the mesolophid and posterolophid are fused as a unique ridge and the posterior valley is absent.

Differential diagnosis: Simplomys meulenorum sp. nov. differs from S. simplicidens by having a less developed centrolophid and by its less reduced and simplified premolars. When these species occur in the same association, S. meulenorum sp. nov. is larger, and the m3 is more reduced and simplified. When the mesolophid and posterolophid of the m3 are fused in a single ridge, in S. meulenorum sp. nov. the last ridge is mainly composed of the posterolophid and the mesolophid is almost completely reduced ( Fig. 8L, P ), whereas in S. simplicidens the last ridge is equally composed of the lingual part of the mesolophid and the labial part of the posterolophid ( Fig. 4H ).

Simplomys meulenorum sp. nov. differs from S. robustus by having a less-developed centrolophid and by the simpler morphology of the posterior part of the m3. When both species co-occur in the same locality S. meulenorum sp. nov. is smaller than S. robustus .

Simplomys meulenorum sp. nov. differs from S. aljaphi by its larger cheek teeth and by having in general a less complicated dental pattern, less developed centrolophid, and by having the posterior part of the m3 more reduced and simplified.

Simplomys meulenorum sp. nov. differs from S. julii by its larger cheek teeth and by having a more concave occlusal surface. In S. meulenorum sp. nov. the central valley of M1 and M2 is narrower and its protoloph–metaloph connection is more pointed than in S. julii . In S. meulenorum sp. nov. the anteroloph and the anterior valley of M1 are not straight as in S. julii .

Etymology: After our friend and colleague Dr Albert J. van der Meulen (Utrecht University, The Netherlands) and his family.

Type locality: Artesilla, Calatayud–Montalbán basin, Spain (local zone C, MN 4, Lower Miocene).

Holotype: m1 left (ART-894 stored at MNCN) Figure 8N .

Paratypes (stored at MNCN)

P4: ART-1142; ART-1148 to ART-1152; ART-1227; ART-1228

M1: ART-870 to ART-876; ART-922; ART-929; ART- 1035

M2: ART-878; ART-879; ART-881 to ART-886; ART- 888; ART-890; ART-950

M3: ART-524; ART-1160; ART-1162 to ART-1168; ART- 1217

p4: ART-1225; ART-2426; ART-2498; ART-2499

m1: ART-891 to ART-898; ART-900 to ART-907

m2: ART-908 to ART-920; ART-984

m3: ART-1154 to ART-1159; ART-1222; ART-1224

Stratigraphical distribution: Local zones A to C (MN 3-MN 4, Lower Miocene).

Material and measurements from localities in the Aragonian type area: Tables 1–3.

Description of Simplomys meulenorum sp. nov.

from Artesilla

P4: The occlusal surface is slightly concave and it has an oval or subtriangular outline. It is small in comparison to the molars. The dental pattern is simple and all specimens have four ridges. The anteroloph is usually short and situated in the middle part of the anterior border. Its labial and lingual parts end free in all the specimens. The anteroloph may be interrupted in its medial part and shows a medial connection with the protoloph in three out of eight specimens. The protoloph is oblique and its lingual end shows a cusp-like shape (protocone). The metaloph is short and its lingual end extends just to the centre of the occlusal surface. Protoloph and metaloph are connected in seven out of eight specimens forming a composite Y-shape. The short isolated posteroloph is situated medially and reaches neither the lingual nor the labial border.

M1: The occlusal surface of the M1 is concave and has a square outline with rounded corners. The most common morphotype shows four main ridges, with the metaloph connected to the protoloph, forming an asymmetric Y-shape, and the anteroloph interrupted and medially connected to the protoloph. The anteroloph is well developed and its labial and lingual parts end free in all specimens. The anteroloph is interrupted in seven out of nine specimens. There is a longitudinal connection between the anteroloph and protoloph in six out of nine specimens. The protoloph is the longest ridge; its lingual part is more oblique than the anteroloph and reaches the posterolingual corner of the occlusal surface. The labial end of the protoloph is curved anteriorly near the border of the tooth. There are no centrolophs. The lingual end of the metaloph shows a slight bend and its labial end is curved backwards. The isolated posteroloph is relatively straight, it reaches neither the lingual nor the labial border.

M2: The occlusal surface of the M2 has a more rectangular outline than the M1. The anteroloph is not divided and there is no longitudinal connection with the protoloph. The anteroloph ends free lingually and it is connected labially to the protoloph in one out of ten specimens. As in the M1, the protoloph is the longest ridge. Its lingual end reaches the posterolingual corner of the occlusal surface. The metaloph is relatively straight. The protoloph and metaloph are connected, forming an asymmetrical Y-shape. Centrolophs are absent. The posteroloph is relatively straight; it reaches neither the lingual nor the labial border. It is labially connected to the metaloph in one out of ten specimens and it is lingually connected to the protoloph in four out of 11 specimens.

M3: The M3 has a concave occlusal surface and trapezoidal outline. The posterior part is narrower than the anterior one and it is slightly rounded. All specimens have four ridges. The labial and lingual ends of the anteroloph are curved backwards, and all specimens have the anteroloph connected labially to the protoloph. The anteroloph and protoloph are always connected labially, whereas they are lingually connected in only four out of ten specimens. As in the M2, the anteroloph is neither divided nor medially connected to the protoloph. The protoloph is curved posterolingually. Its lingual and labial ends are aligned at right angles to the anteroposterior axis of the tooth. Most specimens (eight out of ten) show a strongly asymmetric Y-shaped trigon but in two specimens the protoloph and metaloph are joined on the lingual border and the trigon shows an asymmetric V-shape. Centrolophs are absent. The curve of the metaloph is variable. Its labial part may be directed backwards. The posteroloph is the shortest ridge and ends free labially. The lingual end of the posteroloph reaches the border of the occlusal surface. It is lingually connected to the protoloph in seven out of ten specimens (forming an asymmetric Y-shaped trigon) and to the metaloph in two out of ten specimens (forming a V-shaped trigon). Only in one specimen is the posteroloph lingually free-ending.

p4: The outline of the occlusal surface is oval and slightly concave. The p4 is small compared to the molars and its morphology is simpler than these. The anterior part is occupied by a curved ridge which is assumed to be formed by the union of the anterolophid and metalophid. The mesolophid is very short and connected to the posterolophid near the lingual border in three out of four specimens. There is a narrow trace of the posterior valley.

m1: The occlusal surface is slightly concave, with a subrectangular outline. The anterior part is narrower than the posterior one. The short anterolophid is slightly curved. Its labial part ends free in all specimens and does not reach the labial border of the tooth. The metalophid is sharply bent and its isolated labial end constitutes the anterolabial corner of the tooth, whereas its lingual border does not reach the anterolingual corner, but is connected to the anterolophid in 11 out of 14 specimens. The centrolophid is absent (three out of 14 specimens) or is poorly developed. This ridge, interpreted as a residual centrolophid, extends along the lingual border instead of into the central valley. The centrolophid, metalophid, and anterolophid are connected at the lingual border of the tooth in six out of 14 specimens. Only two specimens show a short isolated centrolophid. The mesolophid is bent and its lingual part is directed anteriorly. The posterolophid is the longest ridge and is more curved than the mesolophid. These ridges are connected lingually in eight out of 14 specimens.

m2: The m2 differs from m 1 in having a more rectangular outline, but its morphology is very similar. In general, the anterolophid is not as short as the m1 and its labial end neither reaches the border of the tooth nor joins the metalophid. The angle of the metalophid, situated in its middle part, is less acute than in the m1. The metalophid ends behind the anterolingual corner of the tooth and is connected to the anterolophid in eight out of 12 specimens. In 11 out of 12 specimens a small ridge, interpreted as a residual centrolophid, extends along the lingual border, sometimes almost reaching the mesolophid. In one specimen this structure is absent. The centrolophid, metalophid, and anterolophid are connected at the lingual border in four out of 12 specimens. In the remaining specimen, the centrolophid is connected to the metalophid. The centrolophid is isolated in four out of 12 specimens but connected to the lingual border of the anterolophid in three out of 12 specimens. The mesolophid is less bent than in the m1 and is lingually connected to the posterolophid in six out of 12 specimens. The posterolophid is as described in the m1.

m3: The occlusal surface is not very concave and its outline forms a half-ellipse. The anterolophid and metalophid are connected lingually in eight out of nine specimens. The centrolophid is more variable than in m1 and m2 and it is absent in five out of nine specimens. The centrolophid is isolated in one specimen; in the remaining specimens with a centrolophid (three out of nine) it is connected to the metalophid and the anterolophid at the lingual border of the tooth. The posterior part of the m3 is rounded, narrow, and very simplified in all specimens. The mesolophid and posterolophid are fused, forming a single composite posterior ridge and the posterior valley is absent in eight out of nine specimens. In the remaining specimen, the mesolophid is a very small, cusp-like, ridge connected to the posterolophid, but separated from it by a narrow trace of the posterior valley.

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 8. Simplomys meulenorum sp. nov. from Artesilla (collection MNCN). A, P4 ART-1142. B, M1 ART-874. C, M2 ART-882. D, M3 ART-1164. E, P4 ART-1227. F, M1 ART-873. G, M2 ART-886. H, M3 ART-1163. I, p4 ART-2498. J, m1 ART-901. K, m2 ART-910. L, m3 ART-1156. M, p4 ART-2499. N, m1 ART-894 holotype. O, m2 ART-918. P, m3 ART-1158. Right side specimens underlined. Holotype in italics.