Miostrellus, RACHL, 1983

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 : 231-232

Miostrellus (sp. n.)

Text-fig. 1d, e, g, m

M a t e r i a l a n d m e a s u r e m e n t s. Forsthart, BSP 1959 XXVII-Ch6 ( Text-fig. 1m ), the right C sup. 0.98 × 0.73 × 1.60; BSP 1959 XXVII-Ch1 ( Text-fig. 1e ), the right M1 1.30 × 1.50; BSP 1959 XXVII-Ch3 ( Text-fig. 1g ), the left M3, LM3 = ca. 0.85; BSP 1959 XXVII-Ch10 ( Text-fig. 1d ), the left m3 1.30 × ca. 0.75 × ca. 0.65.

D e s c r i p t i o n. The M1 ( Text-fig. 1e ) has no conules, but shows a distinct paraloph. The postprotocrista extends posteriorly to the base of the metacone, thus the trigon basin is closed. The crown has neither the hypocone nor the posterolingual talon. The considerable expansion of the posterobuccal part of the ectoflexus cingulum forms a wide and flat posterobuccal shelf.

The M3 ( Text-fig. 1g ) is much damaged: the stylocone and the most part of paracrista are broken, a small part of paracone, the metacone and the protocone are preserved. The metacone is somewhat reduced, thus, the tooth crown is slightly compressed.

The crowns of both the upper canine and the m3 (Textfig. 1d) were broken, but were later restored by being glued together. The upper canine ( Text-fig. 1m ) is slender and triangular in cross-section. It is shaped by a well-developed cingulum, and shows distinct posterior and lingual crests. The buccal crest is weak, but also visible. The posterobuccal face is slightly concave. The posterolingual concavity is wide.

The lingual part of the talonid of m3, including the entoconid, is broken ( Text-fig. 1d ). However, some parts of the hypoconilid and entoconid, as well as the postcristid and the hypoconid are preserved. The trigonid is also damaged: the tips of the paraconid and protoconid are broken, and the metaconid is heavily damaged. Nevertheless, the lower molar is evidently myotodont, with a slightly reduced talonid.

C o m p a r i s o n. According to the general appearance of the crowns, all fossils evidently belong to vespertilionid bats.

The M1 from Forsthart is similar to the Miostrellus in general appearance of the first upper molar crown, which has a distinct paraloph, but neither paraconule nor hypocone. This fossil is most similar to the M1 of M. risgoviensis (e.g., BSP 1966 XXXIV705; see also Rachl 1983: 229, fig. 70c), but the Forsthart fossil is appreciably larger in size (compare with Rachl 1983: 226, tab. 52). It is close in size to the Early Miocene M. petersbuchensis ( Rosina and Rummel 2012: tab. S7, supplementary data). However, the Forsthart fossil is effectively distinguishable from M. petersbuchensis in having a high postprotocrista, which extends to the base of the metacone without any metaloph, and a weaker protocone area (compare with Rosina and Rummel 2012: 471, fig. 5A). The M1 from Forsthart shares these traits with M1 of M. risgoviensis, which is much smaller. The Middle Miocene M. noctuloides from Sansan (e.g., specimens Sa. 13.617-618, MN 6, France; Baudelot 1972) and M. aff. noctuloides from Sandelzhausen (MN 5, Germany; Ziegler 2000) are very close in size to the Miostrellus sp. from Forsthart ( Baudelot 1972: 53). However, the latter differs from both the M. noctuloides from Sansan and the M. aff. noctuloides from Sandelzhausen in the lack of a hypocone (compare with Baudelot 1972: 57, 369, fig. 21, pl. II, figs 10–11, Ziegler 2003: 462, fig. 3.3, Ziegler 2000: 127, pl. 10, fig. 120). Due to this feature, the Miostrellus from Forsthart is also separated from the Early Miocene Eptesicus aurelianensis ZIEGLER, 1993 (Wintershof- West, Stubersheim 3, Germany, MN 3; Ziegler 1993, 1994), the M1 of which have a distinct hypocone and something like a metaloph (specimens BSP 1980 XXX II 641, SMNS 45744 H1; Ziegler 1994: 113, pl. 5, figs 5–6).

The M3is similar to the Early Miocene M.petersbuchensis from Petersbuch ( Rosina and Rummel 2012: 471, fig. 5A) and M. aff. noctuloides from Sandelzhausen ( Ziegler 2000: 127, pl. 10, fig. 122) in the somewhat compressed shape of the crown, due to a less developed metacone, and in having a well-developed cingulum. However, the Forsthart fossil is somewhat larger (compare with Rosina and Rummel 2012: tab. S7, supplementary data, Ziegler 2000: 101, tab. 7). Moreover, it corresponds in size to specimen BSP 1959 XXVII-Ch1.

Despite the damage, the upper canine crown can be seen to be triangular in cross-section, its posterobuccal face is slightly concave, and the lingual talon is absent. All these features of the upper canine from Forsthart are shared with those of Miostrellus risgoviensis (e.g., BSP 1966 XXXIV705; see also Rachl 1983: 229, fig. 70c), but the Forsthart canine is somewhat larger ( Rachl 1983: 226, tab. 52). It is close in size to specimen BSP 1959 XXVIII630-2 of cf. Vespertilio sp. from Rembach, but differs from it primarily in the lack of the lingual talon and in having a slightly concaved posterobuccal face ( Text-fig. 1m 2 ). On the other hand, the Forsthart canine is very similar in size to the upper canines of M. aff. noctuloides from Sandelzhausen ( Ziegler 2000: 101, tab. 7), and appears to correspond in size to other specimen of Miostrellus from Forsthart (BSP 1959 XXVII-Ch1).

The m3 from Forsthart is similar to Miostrellus in appearing to have a somewhat reduced talonid. In addition, it has a somewhat elongated paralophid, as in Miostrellus petersbuchensis , and is very similar to the latter in size ( Rosina and Rummel 2012: tab. S7, supplementary data). The m3 from Forsthart differs from the M. aff. noctuloides from Sandelzhausen in being larger ( Ziegler 2000: 101, tab. 7). Nevertheless, according to all the above listed morphological features, we assign all these specimens from Forsthart to the genus Miostrellus .

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.