Trilophomys depereti Fejfar, 1961

Popov, Vasil V., 2004, Pliocene small mammals (Mammalia, Lipotyphla, Chiroptera, Lagomorpha, Rodentia) from Muselievo (North Bulgaria), Geodiversitas 26 (3), pp. 403-491 : 472-474

Trilophomys depereti Fejfar, 1961 ( Fig. 38 )

Trilophomys depereti Fejfar, 1961b: 71-73 , abb. 10, b, e. — Brandy 1979: 107, 110-112, fig. 17f, g.

MATERIAL EXAMINED. — 1 m 1 (Ms52), 2 m 2 (Ms53- 54), 1 m 3 (Ms55), 1 M1 (Ms56), 2 M2 (Ms57, Ms58), 1 M3 (Ms140).

MEASUREMENTS (maximal length at the base of the crown). — Lm1 = 2.05; 1.85; Lm2 = 1.65; 1.67; Lm3 = 1.10; LM1 = 1.85; LM2 = 1.55; LM3 = 1.47.

DESCRIPTION

m1: the tooth is two-rooted, the crown is high, and the enamel free areas are moderately high. The occlusal surface comprises a posterior loop, two opposite triangles and a rhomboidal anterior cap. There is a well pronounced but shallow antero-lingual reentrant fold. The enamel is not differentiated.

m2: two roots. The dentine tracks at the sides of the crown, although not very high are well pronounced. The occlusal surface consists of three more or less rhomboidal dentine fields, well separated one from the other by deep opposite reentrant angles. The triangles are clearly asymmetrical – the lingual ones are larger than the labial ones.

m3: this tooth has two roots, which are nearly coalescent. The anterior dentine track is high. There is a shallow and ephemeral anterolabial infold, which would vanish quickly with further wear. The lingual reentrant fold is well pronounced transversely, while the postero-labial one is shallow. These folds separate the occlusal surface in two rhomboidal dentinal spaces, which are more or less isolated from each other.

M1: the tooth is with three roots, of which the anterior is larger. The posterior dentine track is rather high, reaching the occlusal surface even in a relatively early stage of wear. The irregular triangles, situated behind the anterior dentine field are distinctly alternating. The posterior two triangles are in relatively wide confluence while the remaining ones are more or less well separated.

M2: the tooth possesses three roots. The anterolingual is the larger one and consists of two completely fused though clearly recognizable elements, which in turn tend to fuse with the anterolabial root. The posterior dentine track is high. The triangles are alternate and more or less confluent.

M3: the occlusal surface is simple, consisting of two largely confluenting dentine fields, separated by two, lingual and labial, shallow reentrant angles.

REMARKS

The genus Trilophomys introduced by Depéret in 1892 from Perpignan ( France) is later found in many other early Pliocene MN14-15 localities in Europe ( Fejfar & Repenning 1998). Up to now the following species have been described: Trilophomys pyrenaicus (Depéret, 1892) , T. depereti Fejfar, 1961 , T. schaubi Fejfar, 1961 , and T. vandeweedi Brandy, 1979 . Sulimski (1964) synonymizes T. schaubi , T. depereti , and T. pyrenaicus , and refers the material from Weze 1 to the last species. The synonymy of T. schaubi and T. pyrenaicus is also confirmed by Brandy (1979). In his analysis, based mainly on the degree of hypsodonty, he recognized two evolutionary lineages of Trilophomys . The first lineage represents the evolution from T. pyrenaicus to T. vandeweerdi . The last species is the most advanced form, particularly the populations from Layna, Balaruc II and IV, Seynes ( France), and Wölfersheim ( Germany) ( Fejfar & Repenning 1998). The second lineage, with relatively high dentine tracks, is poorly known and includes some chronopopulations (Ivanovce, Weze) of T. depereti . Brandy (1979) regards the dental pattern of the specimen from Weze 1, illustrated on figure 14 in Sulimski (1964: 192) to be different from T. pyrenaicus and belonging to the second evolutionary lineage. It is more evolved (more hypsodont with higher enamel-free areas) in comparison with the material of T. depereti from Ivanovce. Brandy (1979) designates the population from Weze 1 as Trilophomys cf. depereti (see also Nadachowski 1990). The available m1 from Muselievo is more primitive than the tooth from Weze 1 ( Sulimski 1964: fig. 14) in its lower dentine tracks. It fits with the material of T. depereti from Ivanovce in having a comparable level of hypsodonty. It can be assumed that the geological age of the remains from Muselievo is closer to that of Ivanovce. However, the m1 from Muselievo has more elaborated anterior part (the presence of a shallow antero-lingual reentrant angle), being more similar with the type specimen of T. schaubi from Ivanovce and with the specimen from Weze 1, illustrated by Sulimski (1964) on figure 14a. However, Sulimski (1964), by a series of sections, showed that the pattern of the occlusal surface varies with the attrition of the crown, argumenting in this way the synonymy of T. shaubi with T. depereti . Hence, the determination of the material from Muselievo is based mainly on the level of hypsodonty. In accordance with the evolutionary scheme proposed by Brandy (1979), I assign the material from Muselievo to T. depereti .

Figures

FIG. 38. — Trilophomys depereti Fejfar, 1961; A, right m1, Ms52, occlusal view; B, the same, labial view; C, left m2, Ms53, occlusal view; D, the same, buccal view; E, left m3, Ms55, occlusal view; F, the same, buccal view; G, left M1, Ms56, occlusal view; H, the same, buccal view; I, left M2, Ms57, occlusal view; J, the same, buccal view; K, left M3, Ms140, occlusal view; L, the same, buccal view. Scale bar: 1 mm.