Miniopterus cf. approximatus Woloszyn, 1988

Popov, Vasil V., 2004, Pliocene small mammals (Mammalia, Lipotyphla, Chiroptera, Lagomorpha, Rodentia) from Muselievo (North Bulgaria), Geodiversitas 26 (3), pp. 403-491 : 434-437

Miniopterus cf. approximatus Woloszyn, 1988 ( Figs 17 ; 18 )

MATERIAL EXAMINED. — 8 fragments of mandible with: c1-m1 (Ms201), m2-m3 (Ms202, 212), m1-m2 (Ms207), m1 (Ms213), m2 (Ms208, 209), m3 (Ms210); 7 mandibular fragments without teeth (Ms211, 221); 36 C1 (Ms203, 217, 218); 2 M1 (Ms204, 220); 4 M2 (Ms205, 220); 1 M3 (Ms206); 4 c1 (Ms214); 6 m 1-2 (Ms215); 1 m 3 (Ms218); 4 distal fragments of humerus (Ms222).

MEASUREMENTS. — See Table 6.

DESCRIPTION AND COMPARISONS

C1: the basal cross-section is elliptical with longer axis parallel to tooth row; the cingulum is well developed; there are four grooves along the crown, the anterior furrow is particularly narrow and deep.

M1: in occlusal view, the outline of this tooth is subrectangular with a well pronounced posterolingual talon; the parastyle is well developed forming a right angle with the preparacrista; the tooth is provided with a metaconule, paraloph and metaloph; both lingual and posterior cingula are well developed while the anterior one is lacking.

M2: the tooth resembles the M1, except for the smaller talon and the obtuse angle between the parastyle and preparacrista.

M3: in occlusal view, the tooth has a subtriangular crown, elongated transversely with respect to the tooth row; the parastyle is similar to that of other upper molars, but smaller; the preparacrista is the longest crista.

c1: it possesses a rounded postero-lingual edge, while in the recent species it is better developed and sharper. The lingual cingulum is poorly pronounced slightly incurved upwards, forming anteriorly a poor protrusion; in the modern species, Miniopterus schreibersii (Kuhl, 1819) , this cingulum is well developed, clearly bent up, rising higher upward, and forming a distinct antero-lingual swelling. The talonid is poorly pronounced, forming a small surface in the postero-lingual border of the crown, while in the modern species it is well developed along the whole rear margin of the crown.

The crowns of p2 and p3 are loosely spaced and barely touch at the margins of the cingula. The crowns of p3 and p4, although contiguous, do not overlap in their lingual margins and, as a consequence, in p4 there is not a protruding antero-lingual corner; in contrast, in the recent species the lingual parts of the crowns overlap and as a results there is a well pronounced anterolingual angle on p4. In general, the crowns of p2- p4 are less compressed antero-posteriorly than in the recent species. In particular, in labial view, the ventral margins of the crowns of p2 and p3 are slightly convex in the fossil form, whereas in the recent species the margins projects considerably ventrally and as a result their cingula have a form of an asymmetrical V in labial view. The crowns of p3 and p4 are longer than wide, while in the modern species the situation reversed.

In labial view, the crown of p2 is slightly lower than that of p3, while in the recent species they are equally high.

p2 has no tubercle on the antero-lingual cingular margin, while in the modern species this bulge is well developed; the crown cross-section is irregularly oval.

p3 is two-rooted; in occlusal view, the crown is trapezoidal or subrectangular.

p4 shows trapezoidal outline in occlusal view, orally tapering, with nearly straight labial margin; it is longer than wide. In the living species this tooth is wider than long, at most squarish, with a clearly convex labial margin (occlusal view). The labial ridge running from the tip reaches the postero-lingual edge of the crown, forming a well pronounced angle at this place. In the recent comparative material, this ridge does not reach the crown margin and there is no postero-lingual angle as seen in occlusal view. The labial cingulum on m1 is wider under hypo- and protoconid, while on m2 it is uniformly narrow.

m1-m2: nyctalodontic. In labial view the ventral margin of the crown has two convexities each towards a root, and a concavity between the roots; this medial concavity is however shallower than in the recent species, indicating that these molars are not so compressed antero-posteriorly as in the modern species. The labial cingulum of m1 is wider under the hypo- and protoconid, while this cingulum is uniformly narrow in m2 and m3.

m3: nyctalodontic; in labial view, the ventral margin of the crown is nearly straight. The talonid is slightly narrower than the trigonid.

REMARKS

Many features of the available remains such as a two rooted p3, nyctalodontic lower molars, a well developed postero-lingual talon on M1 and M2, etc., clearly indicate that they are referable to the genus Miniopterus . In general morphology the material is similar to the extant species Miniopterus schreibersii , though the lower right mandible from Muselievo, carrying c1-m1, shows some differences. These concern the anterior part of the lower tooth row: it is more elongated because the canine and premolars, especially p3 and p4, are less compressed oro-caudally and these teeth are more loosely spaced than in the modern species. Having in mind that the shortening of the anterior part of tooth row, as shown above and as pointed out by Topál (1979), is one of the best markers of the evolutionary degree in many bat phyletic lineages, it might be considered that the characters that differentiate the fossil material from Muselievo are in less evolved state than in the modern species from North Bulgaria. In this respect it is similar to the Pliocene (MN14) species, Miniopterus approximatus , described from Podlesice, Poland ( Woloszyn 1988). On the other hand, the material from Muselievo differs considerably in having longer lower molars. In this respect, it is closer to the extant species. These comparisons, as well as the age of our material (see below), younger than the form from Podlesice, show that the remains from Muselievo represent an intermediate evolutionary stage between the Pliocene form from Poland and the modern species. The presence of such a transitive form in Muselievo constitutes an important fact, which substantiates the Woloszyn’s (1988) assumption for “the probable phylogenetic links” between M. approximatus and the present-day M. schreibersii . Unfortunately, owing to a lack of sufficient material it is at present impossible to analyze these relationships in a reliable detail. For the time being, the remains from Muselievo are tentatively referred to M. approximatus based on their less specialized nature.

Order LAGOMORPHA Brandt, 1855

Figures

FIG. 17. — Miniopterus cf. approximatus Woloszyn, 1988; A, right fragment of mandible with p4-m1, Ms201, occlusal view; B, the same, labial view; C, the same, lingual view. Scale bar: 1 mm.

FIG. 18. — Miniopterus cf. approximatus Woloszyn, 1988; A, right upper canine, Ms203, labial view; B, the same, lingual view; C, the same,occlusal view;D, right M2, Ms205, occlusal view; E, left M1, Ms204,occlusal view; F, right M3, Ms206,occlusal view;G, fragment of right mandible with m2, m3, Ms202, occlusal view; H, the same, labial view; I, the same, lingual view. Scale bar: 1 mm.