Blackia miocaenica Mein, 1970

Laere, Gaëlle Van & Mörs, Thomas, 2023, Beavers and flying squirrels (Rodentia: Castoridae, Pteromyini) from the Late Pliocene of Hambach 11 C, Germany, Geodiversitas 45 (7), pp. 223-241 : 234

Blackia miocaenica Mein, 1970

( Fig. 8 )

MATERIAL EXAMINED. — A left M3 ( IPB-HaR-5636 ).

MEASUREMENTS. — See Table 3.

DESCRIPTION

M3 – HaR-5636 ( Fig. 8A )

This tooth is triangular and has a deep trigon basin with rugose enamel. The protocone is very marked with no accessory inner loph. The anterior valley delimited by the parallel anteroloph and protoloph, exhibits some rugosity although less marked than in the trigon basin. The paracone and metacone, while also marked, are dominated by the protocone. The protocone is linked to the paracone by a low protoloph and to the metacone by a low posteroloph. The anteroloph is low as well and the parastyle is very small. There is no mesostyle. Two roots are preserved, one is broken, one is under the protocone and the other is on the posterior side of the tooth. Both are tilting posteriorly but the root under the protocone has more length preserved. The posterior root seems to be oval.

REMARKS

The small size, simple morphology coupled with the lack of metaloph on the M3, and the granulated enamel ( Mein 1970) of this specimen easily permit its attribution to the genus Blackia , a genus of small sized flying squirrels. Because our specimen is an M3 whereas most specimens in the literature are M1/2 and m1/2 comparisons are difficult. We found that its dimensions are similar to those of the left M3 of Blackia miocaenica from the Late Miocene (MN9) of Richardhof-Golfplatz in Daxner-Höck (2004) and the M3s from the Miocene of Oberdorf ( de Bruijn 1998) as well as the Miocene tooth from La Grive mentioned in Mein (1970). It is smaller than the ones from the Early Miocene of Aliveri ( de Bruijn et al. 1980). de Bruijn (1999) accepts only two species in this genus, B. miocaenica Mein, 1970 and Blackia woelfersheimensis Mein, 1970 . Additionally, in the original diagnoses of the species, ( Mein 1970) states that B. woelfersheimensis is slightly bigger than B. miocaenica . However, this is inconsistent in the more recent literature. For example, the molar in Fejfar & Storch (1990) from the Pliocene of Gundersheim is assigned to B. woelfersheimensis despite being in the range of B. miocaenica and smaller than the specimens of de Bruijn et al. (1980) from the Early Miocene of Aliveri, assigned to B. miocaenica . Considering the similarity in size ranges and the lack of strong morphological differences between the two species ( Daxner-Höck 1975), we follow here Dahlmann (2001) and consider these two species synonymous, with B. woelfersheimensis being the junior synonym. This interpretation is the one followed by Daxner-Höck (2004), Hellmund & Ziegler (2012) and us. Therefore, and since its size fits well into the species ( Daxner-Höck 2004), we attribute the M2 of Blackia aff. woelfersheimensis from the Pliocene of Hambach in Mörs et al. (1998) to B. miocaenica instead. Blackia has been found in the Late Miocene of Eichkogel (MN11) in Austria ( Daxner-Höck 1975) as well as in the Pliocene Sondershausen Lower Muschelkalk fissure filling (MN15) in Thuringia, Germany ( Hellmund & Ziegler 2012). Both findings have been attributed to B. miocaenica for the reasons discussed above. Blackia has also, as mentioned previously, already been found in the Pliocene of Gundersheim, Wölfersheim, Hambach, and Frechen ( Fejfar & Storch 1990; Mörs et al. 1998; Kolfschoten et al. 1998; Dahlmann 2001). These are the only four other recorded occurrences of Blackia in the Pliocene. Blackia is a rare genus in the German Neogene ( Mörs et al. 1998) with most findings of Miocene age. In the Pliocene, where it finally gets extinct, it seems to be especially rare ( Hellmund & Ziegler 2012). Blackia is considered to be relatively stable in size and morphology from the lower Miocene and throughout the Pliocene ( Daxner-Höck 2004). The occurrence in Hambach 11C is one of the youngest of the genus Blackia , alongside that reported in Mörs et al. (1998) from Hambach 11 and that reported by Kolfschoten et al. (1998) from Frechen, which is the youngest record (MN16b).

Figures

FIG. 8. — A, Blackia miocaenica Mein, 1970 from Hambach 11C, IPB-HaR-5636, left M3; B-K, Pliopetaurista pliocenica from Hambach 11C: B, IPB- HaR-5614, right m1/2; C, IPB- HaR-5625 left m1/2; D, IPB- HaR-5627, right m1/2; E, left m3; F, IPB-HaR-5629, right P4; G, IPB- HaR-5631, left P4; H, IPB- HaR-5632, left M1/2; I, IPB- HaR-5634, right M1/2; J, IPB- HaR-5633, left M1/2; K, IPB- HaR-5635, left M1/2. All the teeth are shown as left teeth, the teeth that have been mirrored are indicated by underlined letters. Scale bar: 1 mm.