Armantomys daamsi (de Visser, 1991)

Ruiz-Sánchez, Francisco J., Murelaga, Xabier, Larrasoaña, Juan C., Freudenthal, Matthijs & Garcés, Miguel, 2012, Hypsodont Myomiminae (Gliridae, Rodentia) from five new localities in the Lower Miocene Tudela Formation (Bardenas Reales, Ebro Basin, Spain) and their bearing on the age of the Agenian-Ramblian boundary, Geodiversitas 34 (3), pp. 645-663 : 654-655

Armantomys daamsi (de Visser in Álvarez-Sierra, Daams, Lacomba, López Martínez, Van Der Meulen, Sesé & De Visser, 1991)

( Fig. 4 F-M)

HOLOTYPE. — SJ-193, right M1 (in Álvarez-Sierra et al. 1991: pl. 8, fig. 3).

TYPE LOCALITY. — San Juan, Ebro Basin, Spain.

LOCALITY AND AGE. — Cuesta Agujeros 2 ( CA 2), Province of Navarre, Spain. Agenian (Local subzone Y2, MN 2).

MATERIAL AND MEASUREMENTS. — See Table 2.

DESCRIPTION

m1

Anterolophid separated from the protoconid by a narrow furrow. Metalophid connected to metaconid. Centrolophid short (1) or absent (4). Mesolophid and posterolophid separated at the entoconid by a shallow furrow (2), or connected (2). The mesolophid is not connected to the mesoconid in one specimen. In the rest it is continuous and connected to the mesoconid.

m2

Anterolophid separated from the protoconid by a deep furrow. Metalophid connected to metaconid. One out of three m2 has a short centrolophid. Mesolophid and posterolophid separated at the entoconid by a shallow furrow. Mesolophid continuous and connected to mesoconid.

m3

The anterolophid is separated from the protoconid by a deep furrow. Metalophid connected to metaconid. Centrolophid absent. In one specimen the mesolophid is connected to the labial end of the posterolophid. In another specimen the mesolophid is of medium length, ending labially free. Mesolophid and posterolophid separated at the entoconid by a deep furrow.

P4

The anteroloph is reduced to an isolated, very short and low cusp. Protoloph continuous with a shallow and narrow furrow halfway (2) or transverse, free and not connected to protocone. Metaloph transverse and not connected to protocone (2) or continuous with a deep furrow near the protocone. Posteroloph long and curved, low connected to protocone and metacone.

M1

The anteroloph joins the paracone and lingually it is separated from the protocone by a shallow furrow. Protoloph oblique and continuous. The metaloph is short and ends free, neither connected to protoloph nor to protocone. No centroloph ridges. Posteroloph connected to protocone and metacone.

M2

Anteroloph transverse and separated from the paracone by a deep furrow. The anteroloph is not connected to the protocone. Protoloph continuous.One out of two specimens has an anterior spur directed towards to the anteroloph and separated from it by a narrow and deep furrow. Metaloph connected to protoloph, forming a Y-pattern. Posteroloph transverse, low or high connected to protocone.

M3

The anteroloph is low connected to the protocone and it is separated from the paracone by a shallow furrow. Protoloph and metaloph form a Y-pattern. Posteroloph connected to protocone and metacone.

REMARKS

The material of Armantomys from CA2 is similar to A. daamsi , described by Álvarez-Sierra et al. (1991) from San Juan. Some differences may be observed. The diagnosis of this species says it is of medium size with an M1,2 that may have one or two short centrolophs and an m1,2 with a short centrolophid (Álvarez-Sierra et al. 1991).

Like in Armantomys from CH 1, the hypsodonty of the upper molars from CA2 is very similar to A. bijmai (Lacomba & Martínez-Salanova 1988: 116, fig. 5), and clearly distinct from the species of large size ( A. aragonensis from the Ramblian and Lower-Middle Aragonian and A. tricristatus from the Middle-Upper Aragonian).

The three P4 from CA2 also have a very similar morphology. These specimens have a very short anteroloph, not connected to protocone and paracone, protoloph continuous or interrupted, transverse metaloph, not connected to protocone and a long posteroloph, joined to protocone and metacone.

The M1,2 from CA2 do not have centroloph ridges. In A. daamsi from San Juan, 4 out of 10 M1 present precentroloph only, three present both centrolophs and three have no centroloph at all. In that locality five out of 15 M2 have a precentroloph. The connection between metaloph and protoloph is an important character to distinguish small-medium sized Armantomys species. Álvarez-Sierra et al. (1991) do not specify the connections between metaloph and protoloph. Nevertheless, the holotype M1 of A.daamsi has a free-ending metaloph, not connected to the protoloph (SJ-G 193). The connection between metaloph and protoloph is constant in the M2 from San Juan (Álvarez-Sierra et al. 1991). In CA2 there is an almost complete M1 ( Fig. 4F ) with a short metaloph not connected to the protoloph. On the other hand, all M2 from CA2 have a metaloph connected to the protoloph. The M3 from CA2 also presents a forward directed metaloph, connected to the protoloph. In A. bijmai from the localities of the Ebro Basin (Lacomba & Martínez- Salanova 1988) the connection between metaloph and protoloph is characteristic in all upper molars. On the contrary, in several M1 of A. daamsi from the type locality the metaloph is not connected to the protoloph and in the rest of the upper molars (M2,3) this connection is constant. This is identical to the upper molars of Armantomys from CA2. On the other hand, the distinction between A. daamsi and A. jasperi is based on the metaloph-protoloph connection in M3. This connection is constant in A. daamsi and variable in A. jasperi ( Daams 1990) .

The m3 from San Juan have an anterior side very similar to m1,2 (Álvarez-Sierra et al. 1991). In the majority of the m3 from San Juan (72%) mesolophid and posterolophid form a Y. In the rest of the material, mesolophid and posterolophid form a composite ridge (14%) or the mesolophid ends labially free (14%). The morphology and size of the m3 from CA2 is very similar to the material of A. daamsi from San Juan described by Álvarez-Sierra et al. (1991) and with a more complicated dental pattern than described by Daams (1990) for A. parsani .

Figures

FIG. 4. — A-E, Armantomys cf. bijmai from Cabezo Hermoso 1 (CH1): A, left M2,CH1-6;B, right M3,CH1-8; C, right P4,CH1-4;D, right D4, CH1-5; E, right m1, CH1-3; F-M, Armantomys daamsi from Cuesta Agujeros 2 (CA2): F, left M1, CA2/1-6; G, right M2, CA2/1-5; H, right M2, CA2/2-6; I, right M3, CA2/1-15; J, right P4, CA2/1-12; K, left m1, CA2/1-8; L, left m1, CA2/1-10; M, right m3, CA2/2-5; N, Armantomys cf. jasperi from Cuesta Agujeros 4 (CA4), fragmentary right m2, CA4/1-27; O, P, Armantomys cf. parsani from Cuesta Agujeros 3 (CA3): O, left M2, CA3-1; P, left P4, CA3-2; Q, R, Armantomys cf. daamsi from Cabezo Carboneras 1 (CC1): Q, right M1, CC1-31; R, left M2, CC1-38; S, cf. Praearmantomys crusafonti from Cabezo Carboneras 1 (CC1), right m3, CC1-22. Scale bar:1 mm.