Pliospalax cf. macoveii (Simionescu, 1930)

Popov, Vasil V., 2004, Pliocene small mammals (Mammalia, Lipotyphla, Chiroptera, Lagomorpha, Rodentia) from Muselievo (North Bulgaria), Geodiversitas 26 (3), pp. 403-491 : 475-477

Pliospalax cf. macoveii (Simionescu, 1930) ( Fig. 39 )

MATERIAL EXAMINED. — 2 M1 (Ms114, 115), 2 M2 (Ms116, 117), 1 M3 (Ms118), 2 m 1 (Ms120, 121), 1 m 3 (Ms119).

MEASUREMENTS (L × W). — M1 = 2.37 × 2.05; 2.37 × 2.05; M2 = 2.00 × 2.00; 1.87 × 2.00; M3 = 1.60 × 1.57; m1 = 2.02 × 1.57; 2.00 × 1.70; m3 = 1.75 × 1.87.

DESCRIPTION

M1: both teeth available possess a mesocone (mesoloph) and a more or less well developed posterior cingulum. The postero-labial reen- t r a n t f o l d i s a n e p h e m e r a l f e a t u r e, w h i c h becomes rapidly narrower and shallower as it descends, until it is represented be a mere groove, which may or may not persist in the worn tooth. In the slightly worn specimen, both the paracone and the metacone are still separated from the mesocone and the hypocone, respectively. The anterior loop is oblique in relation to the mesial axis of the occlusal surface. The teeth are three-rooted.

M2: in the younger stage of wear, the anterolingual and postero-lingual valleys are closed labially. In the other, adult, tooth the posterior islet had already vanished. The tooth possesses three roots.

M3: the tooth belongs to a young specimen with the pulp-cavities still open below. The occlusal surface is e-shaped, due to a nearly crescent shaped reentrant fold.

m1: the teeth available belong to individuals of advanced ontogenetic age, as they are considerably worn. The occlusal surface is simple, elongated antero-posteriorly, S-shaped with two reentrant folds (one lingual and one labial), and an enamel island which corresponds to the postero-lingual reentrant fold, separating the entoconid from the posterior cingulum. The lingual sinus is obliquely directed forward, while the posterior one is more or less transversal in relation to the sagital axis of the occlusal surface. Two roots.

m3: the occlusal surface is nearly S-shaped but at this stage of attrition the posterior loop is shut off from the anterior part.

REMARKS

The determination of isolated molars of spalacids is difficult because the occlusal pattern is relatively simple and uniform within the genera but varies considerably with crown wear ( De Bruijn & Van der Meulen 1975; Sen 1977). As a result, similar morphotypes may occur in the related species. According to the structure of the occlusal surface, the available M1s show some similarities with the most primitive species within the genus, Pliospalax compositidontus : small size, occurrence of a mesocone, a well pronounced posterior cingulum and a postero-lingual reentrant fold, three roots. These peculiarities differentiate the specimens from the latter species, Pliospalax macoveii (Simionescu, 1930) and P. odessanus (Topacevsky, 1969) ( Topachevsky 1969) . In particular, P. macoveii and P. odessanus have more simplified occlusal surface of upper molars, a reduced number of roots, and larger size, which, according to Topachevsky (1969), is a result of an evolutionary trend whitin this evolutionary branch. On the other hand, a latter form from the early Pleistocene of Greece (Tourkobounia-1, Athens), described as Pliospalax tourkobounensis De Bruijn & Van der Meulen, 1975 , does not fit within this trend. According to De Bruijn & Van der Meulen (1975) “the stratigraphically youngest of these three species [ P. macovei , P. sotirisi ], P. tourkobounensis , is morphologically more archaic having relatively low-crowned cheek teeth and a mesoloph and posterior cingulum in M1”. It is remarkable that some of the first upper molars from Çalta ( Sen 1977: pl. XIII: 1, 3a), initially attributed to Pliospalax compositidontus , are also very similar to these of P. tourkobounensis and to the M1s from Muselievo in having a mesocone and a postero labial reentrant forld. According to Sen (1998), these molars should also be referred to Pliospalax macoveii . It should be mentioned that these three forms (Tourkoubonia 1, Çalta, and Muselievo) have relatively small molars, similar to these of Pliospalax compositidontus , but considerably smaller than the molars of Pliospalax macoveii and P. odessanus ( Topachevsky 1969) .

In contrast to the upper molars, the first lower molars from Tourkobounia 1 ( P. tourkobounensis ), Çalta ( P. macoveii ), and especially these from Muselievo have a simplified occlusal pattern, quite different from the respective teeth of Pliospalax compositidontus , as figured in Topachevsky (1969: 18, fig. 6). In this respect they are similar to the first lower molars of Pliospalax macoveii and P. odessanus ( Topachevsky 1969; De Bruijn 1984), but, as in the case of the upper molars, they are smaller. As concern the first lower molars from Muselievo, it must be emphasized that they are rather worn, which prevents more detailed comparisons.

The mole rate from Maritsa (isle of Rhodes), initially described as Spalax sotirisi De Bruijn, Dawson & Mein, 1970 , is considered by the latter authors ( De Bruijn & Van der Meulen 1975; Sen 1977) to belong to Pliospalax macoveii . This form shows a simplified occlusal pattern of M1.

The material from Muselievo, the above comparisons and discussion match the opinion of De Bruijn & Van der Meulen (1975) that “the relationship among the Pliospalax species may be rather complex” and, no doubt, the available materials from the southern part of Russian plain, Balkan Peninsula, and Asia Minor need a comprehensive revision. For the time being I refer tentatively the material from Muselievo to P. macoveii on the basis of its overall similarity to the sample from Çalta.

Family HYSTRICIDAE Fischer, 1817

Figures

FIG. 39. — Pliospalax cf. macoveii (Simionescu, 1930); A, left M1, Ms114, occlusal view; K, the same, labial view; B, left M1, Ms115, occlusal view; C, right M2, Ms116, occlusal view; D, right M2, Ms117, occlusal view; E, right M3, Ms118, occlusal view; F, right m3, Ms119, occlusal view; G, right m1, Ms120, occlusal view; J, the same, lingual view; H, left m1, Ms121, occlusal view; I, the same, lingual view. Scale bar: 1 mm.