Hesperoptenus, PETERS, 1868

Rosina, Valentina V. & Rummel, Michael, 2017, The New Early Miocene Bat Records From The Molasse Sites Of South Germany, Fossil Imprint 73 (3 - 4), pp. 227-235 : 228-230

cf. Hesperoptenus (sp. n.)

Text-fig. 1a

M a t e r i a l a n d m e a s u r e m e n t s. Rembach, BSP

1959 XXVIII630-1, right M1 2.23 × 2.70.

D e s c r i p t i o n. The M1 is very massive and compacted, with a regular W-shaped ectoloph. It has a short paracrista and a large protocone. The preprotocrista connects with the paracingulum and extends to the parastyle. The regions of the stylocone and mesostyle are damaged, but they seem to be well developed. The crown is without conules or para- or metalophs, and is shaped by a well-developed cingulum. The postprotocrista extends to the lingual base of the metacone without either the hypocone or posterolingual talon, thus, the trigon basin is closed.

C o m p a r i s o n. In view of all the above characters, the fossil specimen belongs to the family Vespertilionidae . The molar from Rembach is very close in size to those of Otonycteris, Ia and some large species of Eptesicus. However, it differs from both recent and fossil species of these genera in having a closed trigon basin, and a high posterolingual slope of the protocone, lacking any trace of the hypoconal undulation and/or talonal extension ( Text-fig. 1a ; compare with Menu 1985: 115, figs 30–31, Mein and Ginsburg 2002: 24, fig. 38). In these characters, it differs also from Ia lanna MEIN et GINSBURG, 1997 (MN 4 site Li Mae Long of Thailand; Mein and Ginsburg 1997: 801, fig. 11B), and from the European Eptesicus campanensis, which is similar to our fossil in having a closed trigon basin (compare with Rosina and Rummel 2012: 469, fig. 4H).

The shape of the fossil molar crown from Rembach corresponds most to type С of Menu (1985: 115, fig. 32). Indeed, the fossil is similar to the Scotophilus in general appearance of the first upper molar crown, but it is noticeably different from Scotophilus in having a regular W-shaped ectoloph, and by the lack of the posterolingual talon. Precisely in these morphological features the large recent species of Hesperoptenus (tickelii and tomesii) differs from Scotophilus ( Hill 1976: 25) . The Rembach fossil specimen is morphologically most similar in size and in the general appearance of the M1 crown to the large species of Hesperoptenus ( Text-fig. 2 ; see also Hill 1976: pl. 3 figs d–f). In particular, it is much closer to H. tomesii, which is however somewhat large than the Rembach specimen (M1 2.28 × 3.08 in the specimen SMF 69325 of H. tomesii). Furthermore, the first upper molar of H. tomesii differs from the Rembach specimen in having a small but distinct depression of the lingual cingulum separating the protoconal and hypoconal parts of the crown ( Text-fig. 2 ). Therefore, we regard the Rembach specimen as a form close to Hesperoptenus (supposedly belonging to that genus), though obviously not identical with the extant species distributed in the Oriental region. In our opinion, the morphological peculiarities of the Rembach fossil convincingly support its independent taxonomical status. On the other hand, description of a new taxon on the basis of only a single tooth could be inaccurate. In any case, if our interpretations are correct, and the Rembach bat represents the first fossil record of Hesperoptenus , it is the first record of that clade beyond realm of the Oriental region.

For a definite taxonomic conclusion, more material is needed, as well as more detailed information on dental variation in early clades of vespertilionine bats, including the fossil bats, for which no data on maxillary dentition are available. Such a situation exists with Scotophilisis libycus HORÁČEK et al., 2006 from the MN 4–5 site Jebel Zelten ( Libya), and with an articulated skull of Samonycteris majori REVILLIOD, 1922 ( Horáček et al. 2006: 139, fig. 4) from the Late Miocene site of Mytilini (Samos, Greece). The upper molar from Rembach is somewhat similar to the upper molars of the Late Paleogene African genus Philisis ( Sige 1985: 165, fig. 3), which probably belongs to the same phylogenetic clade as Scotophilisis ( Horáček et al. 2006) . Naturally, though, the Oligocene Philisis shows many distinct trends distinguishing it from the cf. Hesperoptenus from Rembach.

R e m a r k s. From the Middle Miocene site of Anwil (MN 7/8, Switzerland), a single upper second molar (specimen Al. 198) was identified by Engesser (1972) as “ Vespertilionidae , Scotophilus ?”. This specimen is very similar in the general appearance of the crown to the Rembach specimen (compare with Engesser 1972: 130, fig. 38), and it is assumed that it could also be classified as Hesperoptenus . If so, the Hesperoptenus from Rembach might not be the sole record of this Oriental genus in Europe.

Figures

Text-fig. 1. a – cf. Hesperoptenus (sp. n.), right M1, BSP 1959 XXVIII630-1, Rembach, occlusal view; b – cf. Vespertilio (sp. n.), right C sup., BSP 1959XXVIII630-2, Rembach; c – Submyotodon petersbuchensis, fragment of right dentary with m3, BSP 1959 XXVIII630-3, Rembach, occlusal view; d – Miostrellus (sp. n.), left m3, BSP 1959 XXVII-Ch10, Forsthart, occlusal view; e – Miostrellus (sp. n.), right M1, BSP 1959 XXVII-Ch1, Forsthart, occlusal view; f – Miostrellus cf. risgoviensis, right M2, BSP 1959 XXVII-Ch2, Forsthart, occlusal view; g – Miostrellus (sp. n.), left M3, BSP 1959 XXVII-Ch3, Forsthart, occlusal view; h – Myotis sp., left m1, BSP 1959 XXVII-Ch9, Forsthart, occlusal view; i – Miostrellus cf. risgoviensis, right C sup., BSP 1959 XXVII- Ch8, Forsthart; j – M. cf. risgoviensis, right C sup., BSP 1959 XXVII-Ch7, Forsthart; k – cf. Miostrellus sp., right C sup., BSP 1959XXVII-Ch4, Forsthart; l – Myotis sp., left C sup., BSP 1959 XXVII-Ch5, Forsthart; m – Miostrellus (sp. n.), right C sup., BSP 1959 XXVII-Ch6, Forsthart; 1 – lingual view, 2 – occlusal view.

Text-fig. 2. a – left M1 of recent Scotophilus dingari, SMF 2515; b – left M1 of recent Hesperoptenus tomesi, SMF 69325; c – right M1 of cf. Hesperoptenus (sp. n.), BSP1959 XXVIII630-1, Rembach, occlusal view (mirror image). Black arrows mark sites of differences between the crowns.