Microdyromys monspeliensis Aguilar 1977
Creators: name: Crespo, Vicente Daniel
name: Ríos, María
name: Marquina-Blasco, Rafael
name: Montoya, Plini
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Gliridae
Microdyromys
Microdyromys monspeliensis

description: Microdyromys aff. monspeliensis Aguilar, 1977
(Fig. 4 A-T)
LOCALITIES. — BC1, MAB0B, MAB3, MAB5, MAB11, CBR0E, and CBR0G.
MATERIAL. — BC1: 2 m2; MAB 0B: 1 d4, 1 M1; MAB3: 2 p4, 4 m1, 2 m2, 1 m3, 2 P4, 6 M1, 3 M2, 2 M3; MAB5: 4 m1, 1 m2, 1 m3, 3 P4, 3 M1, 4 M2, 1 M3; MAB11: 1 M1; CBR 0E: 1 m2, 1 M2; CBR 0G: 1 M3.
MEASUREMENTS. — Appendix 4
DESCRIPTION
d4 (MAB0B)
The tooth is subtriangular in occlusal view with high and fine crestids and narrow valleys. The anterolophid is long. The metalophid is long and isolated and enlarged in the lingual side. The mesolophid and the posterolophid are long, curved, and connected. The posterotropid is well developed.
p4 (MAB 3)
Subtriangular tooth with high, fine crestids and narrow valleys. The anterolophid is short. The metalophid is short and semicircular.The mesolophid and the posterolophid are curved, long and connected. The posterotrophid may be small (1 out of 2) or absent (1 out of 2).
m1 (MAB 3)
Tooth subrectangular in occlusal view. The anterolophid is short. The metalophid is curved. The anteroconid and the metaconid are connected. The centrolophid is longer than half of the tooth width, and perpendicularly connected to the endolophid; in one specimen it is independent. The mesolophid and the posterolophid are long and well-connected. The posterotropid may be large (2 out of 3) or of intermediate size (1 out of 3). The labial cuspids are better developed than the lingual ones. A specimen in the MAB 5 material has an anterotropid, and a better developed posterotropid.
m2 (MAB 3)
The tooth shows a subrectangular outline in occlusal view. The anterolophid is long. The metalophid is longer than in the m1. The anteroconid and the metaconid are connected. The centrolophid is longer than half of the tooth width and perpendicularly connected to the lingual side. The mesolophid and the posterolophid are long and well connected. The posterotropid may be well (2 out of 3) or poorly developed (1 out of 3). The labial cuspids are better developed than the lingual ones. In the BC1 material there is a specimen with anterotropid, a more curved metalophid isolated in the lingual side, and a posterotropid divided in two; in MAB 5 the anterolophid is shorter; in one specimen there is an anterotropid and a more curved metalophid; in CBR 0E the metalophid is also more curved.
m3 (MAB 3)
The tooth is subrectangular in occlusal view. The anterolophid is short. The metalophid is curved. The anteroconid and the metaconid are connected. The centrolophid exceeds half of the tooth width and perpendicularly connected in the lingual side. The mesolophid and the posterolophid are long and well connected. The posterotropid is low. The labial cuspids are better developed than the lingual ones. These characteristics are also found in the MAB 5 material.
P4 (MAB 3)
The tooth has a rounded outline. The endoloph is complete. The anteroloph is short and labially isolated. The protoloph and the metaloph are long, straight and isolated. The precentroloph is long and isolated. The posteroloph is longer than the anteroloph and it is labially isolated. In the MAB 5 material a specimen shows an isolated anteroloph and another specimen a non-isolated centroloph.
M1 (MAB 3)
The tooth is subquadrate in occlusal view. The anteroloph is relatively short. The endoloph is complete and becomes narrower near the anteroloph. The protoloph and the metaloph are independent. The prototrope may be well developed (1 out of 6) or absent (5 out of 6). The precentroloph is longer than half (4 out of 6) or about three-quarters (2 out of 6) of the tooth width. The postcentroloph is short, about half of the tooth width (1 out of 5) or very short (4 out of 5), and it may be either independent (2 out of 5) or not (3 out of 5). The posteroloph is long and without labial connections. The labial cusps are better developed than the lingual ones. The lingual ornamentation is poorly developed. In the material from MAB 0B there is an extra crest in the precentroloph. 2 out of 3 specimens from MAB 5 lack a postcentroloph. On the other hand, the MAB 11 specimens show no significant differences with the material from MAB 3.
M2 (MAB 5)
The outline is subquadrate. The anteroloph may be relatively short (2 out of 4) or long (2 out of 4). The endoloph is complete, although it is narrow in the contact with the anteroloph. The protoloph and the metaloph are independent. The prototrope may be low and short (2 out of 4) or absent (2 out of 4). The precentroloph is well developed to just over half of the tooth width. The postcentroloph may be very short (1 out of 4) or just short (3 out of 4), and it may be independent (3 out of 4) or not (1 out of 4). The posteroloph is short and without connection in the labial side. The labial cusps are more developed than the lingual ones. The lingual ornamentation is poorly developed. In the material from MAB 3 the postcentroloph is mostly independent. The specimen from CBR 0E shows no differences with the described MAB 5 material.
M3 (MAB 3)
The outline of the tooth is trapezoid. The anteroloph is long. The endoloph is complete. The protoloph and the metaloph are independent. The precentroloph may be either longer (1 out of 2) or shorter (1 out of 2) than half of the tooth width. The postcentroloph may be long (1 out of 2) or absent (1 out of 2). The posteroloph is short and without labial connections. The labial cusps are more developed than the lingual ones. The lingual ornamentation is poorly developed. In the CBR 0G material both centrolophs are joined in a single crest; the MAB 5 specimen is similar to the already described MAB 3 material.
REMARKS
This is the smallest and morphologically simplest Microdyromys species found in the Ribesalbes-Alcora Basin. It was described by Aguilar (1977) in the lowermost Miocene (MN1) of France. In the Iberian Peninsula it first appears in the locality of Buñol (local biozone Cb, MN4), and becomes extinct in the local biozone H (MN7/8-9) of the site of Nombrevilla 1 from the Calatayud-Montalbán Basin (Daams 1981).
Later, Daams (1999a) and Vianey-Liaud (2003) proposed that the material assigned to this species in the Iberian Peninsula should instead be ascribed to the species M. legidensis, thus restricting the distribution of M. monspeliensis to the MN 1-2 in Europe. Subsequent authors accept M. monspeliensis as the lowermost Miocene species, while the populations from the uppermost Early Miocene and Middle Miocene are ascribed to M. aff. Monspeliensis, which is probably a new species.
According to the morphological classification of Daams (1981), the rank of abundance of the upper molar morphotypes present in this species are (from most to less abundant): the morphotype G (short precentroloph, long postcentroloph, and without prototrope and metatrope), the morphotype H (long precentroloph, postcentroloph longer than precentroloph, prototrope present and metatrope absent) and the morphotype J (similar to the morphotype H, but with presence of the prototrope). The same abundance pattern is found in the material here studied: predominance of the morphotype G, followed by the morphotype H, while the remaining morphotypes are absent. On the other hand, in the localities of Buñol or Las Planas 4A, the morphotypes G, H, and J are equally abundant (Daams 1981). As for the lower molars, all specimens are included in morphotype 2 (with a posterotropid and a long centrolophid) of Daams (1981), excepting one specimen that belongs to morphotype 3 (similar to morphotype 2, but with an anterotropid). This distribution is like the one observed in the site of Buñol, although in Buñol morphotype 3 is better represented and there is an exceptional appearance of morphotype 1 (without anterotropid, posterotropid and short centrolophid). Biometrically, the material studied here corresponds to the lower size ranges described in Buñol and the sites studied by Daams (1981).
The material described here in the first local biozone of Crespo et al. (2019a), within the Ribesalbes-Alcora Basin, constitutes the oldest known record of this taxon so far.
description: Published as part of Crespo, Vicente Daniel, Ríos, María, Marquina-Blasco, Rafael & Montoya, Plini, 2023, They are all over the place! The exceptional high biodiversity of dormice in the Early Miocene of the Ribesalbes-Alcora Basin (Spain), pp. 589-641 in Geodiversitas 45 (20) on pages 595-598, DOI: 10.5252/geodiversitas2023v45a20, http://zenodo.org/record/10137206