Tenuibrachiatum storchi gen. et sp. nov., 2003

Ziegler, Reinhard, 2003, Moles (Talpidae) from the late Middle Miocene of South Germany, Acta Palaeontologica Polonica 48 (4), pp. 617-648 : 637-640

Tenuibrachiatum storchi gen. et sp. nov.

Fig. 10 .

Etymology: In honour of Dr. Gerhard Storch, Frankfurt, thus appreciating his outstanding contributions to our knowledge of the Tertiary small mammals.

Holotype: Left dentary fragment with p1, p4–m2 and the alveoles of i1, i2, c, p2–p3; NHMA P31−166 A1 , Fig. 10A .

Measurements of the holotype: p1 (0.70×0.43), p4 (0.97×0.58), m1 (1.40×0.88×1.00), m2 (1.54×1.00×0.95), lingual height of the dentary below m1 (1.35).

Type locality: Petersbuch 31 (details see p. 618).

Age : Upper part of the Middle Miocene (MN 7 according to Rummel 2000: 157, means MN 7+8).

Paratypes and measurements.—Petersbuch 31: NHNA P10−166A2 , right dentary with m1, m1 (1.40×0.85×0.91); CRW P31−166A3, right dentary with m1, m1 (1.40×0.78×–); NHMA P10−166A4 , right m2 (1.56×0.97×0.90); CRW P31−166A5, right m2 (1.51×1.02×0.97); CRW P31−166C1, left m3 (1.41×0.88); CRW P31−166C2, left m3 (1.41×0.86); CRW P31−166C3, left m3 (1.44×0.89); CRW P31−166C4, right m3 (1.42×0.85); CRW P31−166C5, right m3 (1.33× 0.82×0.68); CRW P31−166D1, left maxilla fragment with P4, P4 (1.34×1.12); NHMA P31−166D2 , left maxilla fragment with P4–M1, P4 (1.29×1.03), M1 (1.87×1.38); CRW P31−166D3, left M1 (1.95×1.50); CRW P31−166D4, left M1 (–×1.50); CRW P31−166D5, right M1 (1.80×1.38); CRW P31−166E1, left M2 (– ×1.57); NHMA P31−166E2 , right M2 (1.42×1.64); NHMA P31−167 /1, left humerus GL (7.74), Bp (>3.56), BpwT (>3.30), DS (1.44), Bd (3.94), BdwE (3.81); NHMA P31−167 /8, right humerus GL (7.62), Bp (6.63), BpwT (3.33), DS (1.40), BdwE (3.58), Bp*100/GL (47.6); CRW P31−167/2–7, 9–11, 9 humeri .

Diagnosis.—As for the genus.

Description of the holotype

The horizontal ramus from the first incisor alveolus to the fracture behind m2 is preserved. The dentary was broken between p4 and m1 and was glued. It tapers anteriorly. The anterior mental foramen is situated under the anterior root of p2. The posterior foramen beneath the trigonid of m1 is filled with not removable sediment, thus hardly visible. The four alveoli of p2 and p3 are slightly overlapping. There are three alveoli anterior to p1: the first two nearly procumbent, the third slightly inclined anteriorly. They are interpreted as alveoli of i1, i2, and c, resulting in the tooth formula 2143. Alternatively they can be interpreted as i2, i3, and c, resulting in the same tooth formula, or as i1, i2, and i3. In the latter case the tooth formula was 3043. According to their alveoli the size relation is i1>i2>c. The symphysis extends to c/p1. The double−rooted p1 is oval in occlusal outline. Its cusp is situated above the anterior root. There is a weak posterior and lingual cingulid, respectively. The p4 has a postero−lingual and an anterior crest. It is surrounded by a weak cingulum. There is a tiny parastyle and a well−developed heel. In the m1 the oblique cristid terminates far labially, whereas in m2 it ascends and joins the marked metacristid. In the m1 there is only a vestige of a short ectocingulid below the hypoflexid, in the m2 a faint precingulid. Both have a well−developed entostylid.

Description of the paratypes

Dentary.—In two further fragments the posterior mental foramen is situated below the trigonid of m1; in one specimen, like in the type, the p3 is obliquely implanted. The slightly crowded p3 and p2 seem to be a consistent character of the species.

Lower dentition.—With respect to the lower dentition there is no additional information except for the m3. In the last molar the precingulid is more marked, the oblique cristid joins the metacristid. The reduced talonid has no entostylid. In size and morphology all five m3 fit well with one another. However, it cannot be excluded that one or more belong to Urotrichini gen. et sp. indet. II and/or to Desmanella sp. , which is of roughly the same size. The well−developed precingulids of these m3 would argue in favour of the association with Desmanella sp. whose m1 and m2 have well−developed precingulids. However, Desmanella sp. is represented only by six specimens. It is unlikely, that all five m3 belong to this species.

Upper dentition.—The P4 has a tiny parastyle and a well−developed protocone. There is a weak precingulum and a more pronounced postcingulum. The M1 has an undivided mesostyle, hardly differentiated para− and metaconule respectively, a marked paracingulum, which joins the projecting parastyle and a weak metacingulum, which tapers distolabially. In the M2 there is a marked paraconule and a well−developed metaconule. Para− and metacingulum are absent. The mesostyle is undivided.

Humerus.—The associated humeri are the smallest and most gracile ones among the Petersbuch 31 talpid humeri. There is a suite of urotrichine characters: large, pocketed supratrochlear fossa, deep, concave notch between trochlea and the fossa m. flexor digitorum profundus ligament, small and moderately deep brachialis fossa. In anterior view the trochlea is broadening towards the capitulum. The long axis of the elliptical head runs nearly parallel to the shaft. The marked ledge extending from the lesser tubercle to beneath the head is rounded. The olecranon fossa is shallow. The teres tubercle forms a long crest proximally not covered by the pectoral ridge. The pectoral tubercle is situated labially on the shaft. There is a deep groove between head and major tubercle. The passage of the biceps tendon between teres tubercle and pectoral crest is a bicipital notch.

Comparisons

As the material under study without any doubt represents a species of the tribe Urotrichini , the comparisons mainly refer to the fossil and extant species of this tribe. Storch and Qiu (1983: tabes 6 and 7) listed a suite of features characterising both the Recent genera Urotrichus Temminck, 1841 and Neurotrichus Günther, 1880 .

The Recent Urotrichustalpoides Temminck, 1841 and U. pilirostris ( True, 1886) differ from Tenuibrachiatum storchi in the:

– humerus with a long axis of the head directed disto−laterally,

– shorter, proximally angled teres tubercle (see Storch and Qiu 1983: figs. 20, 21),

– pectoral tubercle bent laterally, thus being visible in posterior view,

– dentary with a reduced antemolar region not tapered anteriorly,

– more posterior position of the mental foramina,

– at large more compact teeth (see Hugueney 1972: figs. 16, 17).

? Urotrichus dolichochir ( Gaillard, 1899) from La Grive, originally described as Scaptonyx? dolichochir on the basis of a humerus and tentatively assigned to Urotrichus by Hutchison (1974) shows striking resemblance to the Recent genus. In size and gracility it fits well with the humeri of T. storchi , but they differ in the same characters as the Recent species. The lectotype dentary of “ Scaptonyx ” edwardsi ( Gaillard, 1899) , which Hutchison (1974: 226, pl 38: 1.) “considered a possible candidate for the association with? U. dolichochir ”, has a more reduced antemolar region and m1 and m2 with stronger precingulids.

? Urotrichus dolichochir from Petersbuch 6 is based on a humerus and an assigned dentary fragment (this paper, p. 634). The humerus fits well in size and gracility with the humerus of T. storchi , but the crest running from the lesser tubercle to beneath the head is distinctly weaker and forms no ledge, and the long axis of the head is pointed slightly more disto−laterally with respect to the shaft. The tentatively associated dentary fragment differs in having:

– a reduced antemolar region,

– a p4 with a disto−lingual cuspule,

– a m1 with a better−developed precingulid.

Urotrichus sp. from the uppermost Miocene locality Maramena in Greece is known from nine isolated upper molars (see Doukas et al. 1995). This species differs from Tenuibrachiatum storchi in (see Doukas et al. 1995: 51, table 5, pl. 5): – the distinctly bigger size, – the less differentiated lingual conules of M1 and M2.

Neurotrichus gibbsi ( Baird, 1858) , the Recent species of the genus and Quyania chowi Storch and Qiu, 1983 from the Neogene of Inner Mongolia differ from Tenuibrachiatum storchi in (see Storch and Qiu 1983: tables 6, 7): – lacking two lower antemolars in Neurotrichus (? two premolars) and p 1 in Quyania ; – having only 8 antemolar alveoles (p3 and p4 doublerooted) in Neurotrichus and 10 in Quyania , – the presence of a metaconid on p4, – the presence of a marked precingulid on m1, – the more buccal termination of the oblique cristid of m2 and m3, – the ectocingulid of P4 and the very short premetacrista of M1, – the presence of an metacingulum and the weaker paraconule of m2.

Neurotrichuspolonicus Skoczeń, 1980 from the Pliocene of Poland differs from Tenuibrachiatum storchi in: – being distinctly bigger (see Skoczeń 1980: tables 5, 7), – the morphological characters listed above for N. gibbsi .

Yanshuella columbiana ( Hutchison, 1968) from the Hemphillan (Middle to Late Pliocene) of Oregon originally was tentatively assigned to Neurotrichus , thus being an urotrichine. Storch and Qiu (1983: 111) referred the species to the scalopine genus Yanshuella . This species, only known from the type dentary and some lower teeth, differs from Tenuibrachiatum storchi in having: – distinctly bigger lower molars, – m2 and m3 without metacristid and an oblique cristid terminating more labially, – all lower antemolars between i1 and p4 and single−rooted p1–p3.

Myxomygale antiqua Filhol, 1890 , the earliest urotrichine from the Oligocene in Europe, differs from Tenuibrachiatum in: – its distinctly bigger size, – having the complete set of lower antemolars, but singlerooted lower premolars, – having lower molars with marked pre− and ectocingulids.

Myxomygale vauclusensis Crochet, 1995 from the Oligocene of Southern France differs from Tenuibrachiatum in: – being distinctly bigger, – having lower molars with marked pre− and ectocingulids, – the projecting parastyle of P4, – the presence of para− and metacingulum on M2.

Among the Miocene species of Myxomygale there are two with associated humeri. M.hutchisoni Ziegler 1985 from the Early Miocene of South Germany and M. gracilis sp. nov. from Petersbuch 10. M. hutchisoni differs from Tenuibrachiatum in having:

– the complete set of lower antemolars, but single−rooted lower premolars,

– lower molars with marked pre− and ectocingulids,

– more robust humerus, which shows advanced fossorial adaptations.

M. gracilis differs from Tenuibrachiatum in having:

– lower molars with better developed pre− and ectocingulid respectively,

– M1 without projecting parastyle and with divided mesostyle,

– a slightly bigger humerus with a pectoral tubercle situated more laterally and being visible in posterior view.

Myxomygale engesseri Doukas, 1986 , a poorly recorded species from the Lower Miocene of Greece, differs from Tenuibrachiatum in the:

– better developed cingulids of m2,

– less projecting parastyle of M1,

– hardly developed metaconule of M2.

Myxomygale minor Ziegler, 1990 from the Early Miocene of South Germany is mainly known from isolated teeth. It differs from Tenuibrachiatum in the:

– better developed cingulids of the lower molars,

– projecting parastyle of P4,

– better developed para− and metacingulum of M1 and M2. Paratalpa Lavocat, 1951 is known from the Oligocene species P. micheli Lavocat, 1951 , the Agenian P. micheli saulcetensis Hugueney, 1972 , P. brachychir (von Meyer, 1846) , and P. meyeri ( Schlosser, 1887) . They are all distinctly bigger, have a dentary with a more reduced antemolar region, lower molars with better−developed cingulids and further buccally terminating oblique cristids, upper molars with deeply divided and spaced mesostyles. The humerus, known from P.micheli , P.brachychir , and P.meyeri , is bigger, more robust and has a shorter teres tubercle.

Pseudoparatalpa Lopatin, 1999 is known from its type species, P.shevyrevae Lopatin, 1999 , from the Lower Oligocene and P. lavrovi ( Bendukidze, 1993) from the Lower Miocene of Kazakhstan ( Lopatin 1999). This genus, scarcely represented only by some dental remains, differs from Paratalpa just in the structure of the p4−talonid and the m1−trigonid, in the position of the posterior mental foramen and in its larger size. These differences are sufficient to describe new species, but not to distinguish a new genus. Hence, Pseudoparatalpa is considered a junior synonym of Paratalpa .

Discussion

Both dentition and associated humeri show a suite of urotrichine characters, which leaves the tribal assignation beyond any doubt. I think the association of humeri and dentition is correct. The smallest are expected to belong to the smallest dentition. Additionally, it is assumed that the humeri have to be associated with the dentition that roughly corresponds in the number of specimens. The Petersbuch 31 fauna also yielded four dentary fragments and two m2 of Desmanella , which correspond in size to Tenuibrachiatum . The only Desmanella species with associated humeri is D. engesseri Ziegler, 1985 from the Early Miocene fissure fill Petersbuch 2 ( Ziegler 1985: fig. 2). In this species the teres tubercle is distinctly shorter and forms no ledge. Consequently, we can be rather confident that the association of humeri – dentition for Tenuibrachiatum is correct.

T.storchi cannot be ancestral to the Recent Neurotrichus nor to Quyania . Both have all three lower incisors, whereas one is lost in Tenuibrachiatum . In anterior view the humerus of the later genera shows a narrow trochlea, which is connected to the capitulum by a thin bridge of the articular facets (see Storch and Qiu 1983: figs. 17–19). In the humerus morphology Tenuibrachiatum shows more affinities to Urotrichus . In the extant species the antemolar region is more reduced. Tenuibrachiatum is a possible candidate for the ancestry of Urotrichus . The ancestor of Tenuibrachiatum is expected to have the full set of lower antemolars and double−rooted lower premolars, hence one tooth (?i3) with one additional alveolus. Neither Myxomygale nor Paratalpa fulfil this qualification. In spite of the Oligocene to Early Miocene correlation of most species, both genera are more advanced with respect to the degree of reduction in the lower antemolar region. In dental morphology Tenuibrachiatum is somewhat closer to Myxomygale .

Figures

Fig. 10. Tenuibrachiatum storchi gen. et sp. nov., Petersbuch 31. A. Holotype, left dentary with p1, p4–m2, NHMA P31−166A1, in occlusal (A1) and buccal (A2) views; ca. × 10. B. Right m1, NHMA P31−166A2, occlusal view; ca. × 15. C. Right m2, NHMA P31−166A4, occlusal view; ca. × 15. D. Left maxillary fragment with P4–M1, NHMA P31−166D2, occlusal view; ca. × 15. E. Right M2, NHMA P31−166E2, occlusal view; ca. × 15. F. Left humerus, NHMA P31−167/1, anterior view; ca. × 7.5. G. Right humerus, NHMA P31−167/8, posterior view; ca. × 7.5.