Rhinolophus mehelyi birzebbugensis Storch, 1974

Popov, Vasil V., 2004, Pliocene small mammals (Mammalia, Lipotyphla, Chiroptera, Lagomorpha, Rodentia) from Muselievo (North Bulgaria), Geodiversitas 26 (3), pp. 403-491 : 415-419

Rhinolophus mehelyi birzebbugensis Storch, 1974 ( Fig. 8 )

Rhinolophus mehelyi birzebbugensis Storch, 1974: 414- 417 , abb. 4, 14-17.

Rhinolophus mehelyi – Sevilla 1988: 147-153, figs 25, 26: 1-3, 28, 29: 1-4.

MATERIAL EXAMINED. — 67 fragments of mandible (Ms149:1-67), 1 fragment of maxillae with P4-M3 (Ms150), 118 right C1 (Ms150), 113 left C1 (Ms152), 4 P4 (Ms153), 33 M1 (Ms154), 46 M2 (Ms155), 19 M3 (Ms156), 44 left c1 (Ms157), 72 right c1 (Ms158), 6 p4 (Ms159), 59 m 1 (Ms160), 46 m 2 (Ms161), 28 m 3 (Ms162), 2 fragments of maxillae with P4-M1 and M1-M3 (Ms163), 3 fragments of maxillae with P4-M1, M3 and M2-M3 (Ms164), 18 fragments of humerus (Ms165).

MEASUREMENTS. — See Table 2.

DESCRIPTION AND COMPARISONS

The material from Muselievo is described in comparison with the three medium-sized extant species of horseshoe bats ( Rh. mehelyi Matschie, 1901 ; Rh. euryale Blasius, 1853 ; and Rh. blasii Peters, 1866 ) from Bulgaria ( Popov & Ivanova 2002). Since the form from Muselievo overlaps in many measurements with some modern populations of Rhinolophus ferrumequinum (cf. Sevilla 1988), comparisons with this species have also been included.

C1: the crown is more or less oval, when seen from above; the postero-lingual margin presents a slight concavity, similar in this respect to the three modern medium-sized species, and differing from the recent comparative material of Rh. ferrumequinum , which possesses a convexity in this part of the tooth margin, and showing a depression on the postero-buccal margin of the tooth, resulting of the pressure of P2. In the fossil material, from labial view, the cingulum runs slightly downwards up to the posterior part of the crown, where it starts to run upwards, forming in this way an obtuse angle. In this feature the available upper canines are similar to the recent medium sized species and differ from the recent Rh. ferrumequinum in which the anterior and posterior parts of this cingulum form a right or sharp angle, due to the antero-posterior compression of this tooth.

P2 is not present in the material examined, but the size and position of the alveolus (specimen Ms150), indicate that this tooth must have been of moderate size and slightly displaced labially. In this respect, the fossil material is similar with Rh. blasii , which possess a relatively large P2, laying in the tooth row. As a result, there is a well pronounced depression on the middle part of the anterior margin of P4, pointing to the presence of a pressure from P2. In the other modern species, the P2 is quite reduced, positioned labially to the tooth row, and there is no impression of this tooth on the anterior margin of P4.

P4: the tooth is moderately elongated transversely with respect to the tooth row. This tooth is slightly more elongated in the recent Rh. mehelyi and Rh. euryale and much more in Rh. blasii .

M1-M2: the posterior emargination of these teeth is shallow like in the three modern medium-sized species, whereas in Rh. ferrumequinum the rear margin of the crown has a well pronounced emargination. The recent Rh. blasii differs considerably from the remaining two medium-sized species in having a strongly developed talon on these molars and especially on M1. So, these molars are strongly elongated transversely. In this respect, the fossil material is similar to Rh. mehelyi and Rh. euryale .

M3: the tooth is massive and more elongated transversely than in the recent Rh. mehelyi . In this respect, it is similar with the other two modern medium-sized species. On the other hand, the fossil material differs from the three comparative species in having a proportionately larger M3.

c1: in the crown outline the tooth is an irregular trapezium with convex labial and concave posterior margins. The anterolingual corner is poorly pronounced and rounded as in the modern Rh. mehelyi , whereas in the comparative specimens of Rh. euryale it is sharp. In contrast, this corner is not developed in Rh. blasii , and the outline of its crown in occlusal view is triangular.

p3: this tooth is not preserved, but judging by the size and position of the alveolus, it may be assumed that p3 must have been similar with the recent species Rh. euryale and in a lesser degree with Rh. blasii . These species present moderately reduced p3 situated in the tooth row (some specimens of Rh. blasii ) or slightly shifted laterally (some specimens of Rh. blasii and Rh. euryale ). At the same time it differs from Rh. mehelyi which has more reduced p3 and displaced further labially.

p 4 in the outline of crown is a triangle with rounded corners, with a well developed anterolingual cingular shelf, and straight or slightly concave lingual margin. In these respects, the available teeth are similar to those of the modern comparative specimens of Rh. mehelyi . In the other two medium-sized species, the outline of the crown is a shortened ( Rh. euryale ) or more or less elongated ( Rh. blasii ) trapezium. In Rh. ferrumequinum the p4 is almost square with a poorly developed cingular shelf and convex lingual margin.

m1-m2: the structure of these nyctalodontic molars is similar to those of the recent Rh. mehelyi from Bulgaria though differing in some proportions and dimensions. The m1 deserves special attention in this respect. The length of this tooth is considerably greater than in the recent comparative material, while there is a broad overlap in the talonid breadth ( Table 2). Storch (1974) reported similar relations between the recent and fossil (early Pleistocene) populations of Rh. mehelyi , though the talonid width of m 1 in the Mediterranean modern form is even greater, nearly equal to the average value of the population from Muselievo.

m3: nyctalodontic. As compared with the modern medium-sized species, the form from Muselievo differs in having broadest talonids and larger size of this molar.

Palate: the posterior emargination of the palate is shallow (specimen Ms150) and anteriorly reaches the middle part of the M3. In this respect, the fossil specimen is quite different from the three recent medium-sized species in which this emargination is quite deep, reaching anteriorly the posterior or middle part of the crown of M2.

REMARKS

T h e a b o v e d e s c r i p t i o n s a n d c o m p a r i s o n s suggest that the material examined presents a horseshoe bat of medium size close to the contemporary species Rh. mehelyi . It differs c o n s i d e r a b l y, h o w e v e r, f r o m t h e m o d e r n comparative material in its generally greater size, more elongated m1, etc. In this respect the specimens from Muselievo fit well to the description of the limited early Pleistocene material from Malta, designated as a separate subspecies, Rhinolophus mehelyi birzebbugensis ( Storch 1974) . The rich material from Muselievo and the above comparisons reveal some additional peculiarities of this form: relatively large p4, P4, m3 and M3, less reduced talonid on m3, and probably relatively large P2 and p3 not very shifted from the tooth row, a shallow posterior emargination of the palate.

Having in mind the morphologic evolutionary trends in large horseshoe bats and the general direction of specialization in recent rhi- nolophids (see above), the characters that differentiate the Muselievo material from the modern Rh. mehelyi are of less specialized nature. In this respect, it is somewhat similar to the smaller recent species Rh. euryale and especially to Rh. blasii . However, considering that, according to the recent situation, the large forms should be more specialized in the above respects, the form from Muselievo would fit better in the evolutionary line of Rh. mehelyi and might even be regarded as an ancestor of the recent species. That is why, following Storch (1974), I considered the fossil form as a chrono-subspecies of Rh. mehelyi .

Figures

FIG. 8. — Rhinolophus mehelyi birzebbugensis Storch, 1974; A, right fragment of mandible with p4-m3, Ms149, lingual view; B, the same, labial view; C, the same, occlusal view; D, right lower canine, Ms158-1, lingual view; E, the same, occlusal view; F, the same, buccal view; G, right upper canine, Ms151, buccal view; H, the same, occlusal view; I, the same, lingual view; J, right palatal fragment with P4-M3, Ms150, occlusal view. Scale bar: 1 mm.