LEPORIDAE Gray, 1821

Popov, Vasil V., 2004, Pliocene small mammals (Mammalia, Lipotyphla, Chiroptera, Lagomorpha, Rodentia) from Muselievo (North Bulgaria), Geodiversitas 26 (3), pp. 403-491 : 440-443

Family LEPORIDAE Gray, 1821

Since the species determination of the isolated teeth of Leporidae , others than p3, is problematic when isolated, they are considered separately. Teeth were divided with respect to their morphology into groups referred to as morphotypes. In some cases, it is possible to refer tentatively some morphotypes to one or another species already identified based on p3.

P2 ( Fig. 20 ): the sample consists of 14 teeth (Ms93, 93-1, 2, 97-107, 107-1). Three morphotypes can be singled out based on the degree of development of hypoflexus, paraflexus and mesophlexus: 1) the paraflexus is only pronounced ( Fig. 20J ): two specimens (Ms107, 107- 1). Similar teeth are known in Trischizolagus maritsae De Bruijn, Dawson & Mein, 1970 ; 2) the paraflexus and mesoflexus present but the latter is shallow and wide: six specimens (Ms100- 105) ( Fig. 20 E-I). This pattern occurs in Hypolagus beremendensis ( Petényi, 1864) ( Sych 1965: pl. III, 4a, b); and 3) the three reentrant folds are well pronounced; the paraflexus is the deepest one and tends to have slightly crenulated margins: four teeth (Ms93, 93-1, 93-2, 97-99) ( Fig. 20 A-D). Similar teeth are known in Pratilepus kutschurganicus Topachevsky, 1980 ( Topachevsky 1980: figs 16, 17).

The last two morphotypes are not well individualized because they are connected by many intermediates with variable deepness of the hypoflexus and mesophlexus (Ms106, 93-1, 93-2) ( Fig. 20I ). Some variants of these two morphotypes are known in Pliopentalagus dietrichi (Fejfar, 1961) ( Daxner & Fejfar 1967) .

Upper molariform teeth (P3-M2): four morphotypes can be distinguished based on the degree of waviness of the margins of the hypostria: 1) teeth with wavy walls of the hypostria; 1a) both walls of the hypostria are considerably and irregularly undulated: 21 teeth (Ms108-109, Ms389) ( Fig. 21A, C ); 1b) the walls are regularly folded, forming a sinusoid with a great amplitude but with a short period. The peaks and depressions of the walls are strictly opposite: nine teeth. Most probably, these two subgroups reflect the differences between molariform teeth within the same row, likewise in the recent species Pentalagus furnessi (Stone, 1900) ( Gureev 1964: fig. 58). As concern the fossil forms, the morphotype 1a is known for Pliopentalagus dietrichi ( Fejfar 1961a; Daxner & Fejfar 1967) and for the genus Pratilepus Hibbard, 1939 ( Hibbard 1939) ; 2) both walls of the hypostria are no more than slightly wavy or one of them is smooth: 11 teeth (Ms110 and Ms390, Fig. 21F ); and 3) nearly smooth walls of the hypostria: 2 teeth (Ms111, Fig. 21E ).

The last two morphotypes may be recognized as characteristic of Hypolagus beremendensis ( Sych 1965) and Trischizolagus maritsae ( De Bruijn et al. 1970) . However such teeth are also known for M1 and M 2 in species whose premolars and M1s show heavily folded walls of the hypostria, for instance some species of the genera Pratilepus , Pliopentalagus Gureev & Konkova, 1964 , and Pentalagus Lyon, 1943 .

Lower molariform teeth (p4-m2): the distinction of the three morphotypes is based on the shape of the anterior wall of talonid: 1) the wall is heavily folded ( Fig. 21D ): five teeth (Ms113 and Ms391). Such teeth occur in Pliopentalagus dietrichi ( Fejfar 1961a; Daxner & Fejfar 1967). Most probably all these teeth belong to this species. The degree of undulation is lower than in the recent Pentalagus furnessi ; 2) the wall is slightly wavy or nearly smooth ( Fig. 21G ): 12 teeth (Ms112 and Ms392). This pattern occurs in Hypolagus beremendensis ( Sych 1965: fig. 5), Trischizolagus ( De Bruijn et al. 1970) (= Alilepus Dice, 1931 from Malusteni, Daxner & Fejfar 1967: fig. 5), Pratilepus ( Hibbard 1939) . It is difficult to find any additional features to permit the separation of these teeth between the species identified in the locality (see below).

The sample of Leporinae involves also: 9 upper incisives, 3 lower incisives, 11 upper milk premolars, 19 dp3, 13 dp4, 9 m3 (Ms393).

Figures

FIG. 20. — Leporidae indet., P2 in occlusal view; A, left, Ms93; B, right, Ms97; C, left, Ms98; D, right, Ms99; E, left, Ms100; F, left, Ms101; G, left, Ms102; H, left, Ms103; I, left, Ms106; J, left, Ms107. Scale bar: 1 mm.

FIG. 21. — A, Leporidae, left upper molariform tooth, Ms108, occlusal view; B, Pliopentalagus dietrichi (Fejfar, 1961), right p3, Ms92, occlusal view; C, Leporidae, right upper molariform tooth, Ms109, occlusal view; D, Leporidae, left lower molariform tooth, Ms113, occlusal view; E, Leporidae, left upper molariform tooth, Ms11, occlusal view; F, Leporidae, right, Ms110, occlusal view; G, Leporidae, right lower molariform tooth, Ms112, occlusal view. Scale bar: 1 mm.