Leptoscaptor bavaricum, Ziegler, 2003

Ziegler, Reinhard, 2003, Moles (Talpidae) from the late Middle Miocene of South Germany, Acta Palaeontologica Polonica 48 (4), pp. 617-648 : 620-625

Leptoscaptor bavaricum gen. et sp. nov.

Fig. 2 .

Etymology: From Latin bavaricum, Bavarian. The species is recorded from the state of Bavaria, Germany.

Holotype: Left dentary fragment with c, p2–m1 and the alveoles of i1–i2, P10−608/6, fig. 2A.

Measurementsoftheholotype:lc–p4(3.35),lp2–p4(2.52),c(0.64×0.38), p2 (0.67×0.40), p3 (0.80×0.45), p4 (1.03×0.65), m1 (1.54×0.90×1.16); h of the corpus below the lingual side of m1 (1.80).

Type locality: Petersbuch 10 (details see p. 618).

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

Paratypes (measurements see Tables 1, 2).—Petersbuch 10: NHMA P10−608 /36, 37, 2 left dentary fragments with teeth ; NHMA P10−624 /1+3, 2 left maxilla fragments wilth teeth ; NHMA P10−625D1 +H4, 2 upper molars ; NHMA P10 − 610.2 +612, 2 left humerus fragments; CRW P10−608– 611, 613, 624, 625, 102 dentary fragments with teeth, 27 maxilla fragments with teeth, 44 isolated teeth, 11 humerus fragments, 5 ulna fragments .

Referred material, L. bavaricum vel robustior (measurements see Tables 1, 2).—Petersbuch 6: CRW P6−1063, 5 dentary fragments with teeth; Petersbuch 18: CRW P18−752, 756, 5 dentary fragments with teeth, 2 maxilla fragments with teeth, 5 isolated teeth.

Diagnosis.— Leptoscaptor species with slender humerus and a single mental foramen in the vast majority of the dentaries.

Description of the holotype

Only the horizontal ramus of the dentary anterior to m2 with c and p2–m1 insitu is preserved. The mental foramen is situated beneath the anterior alveolus of p3; the symphysis extends posteriorly to c/p2. The dental formula is reduced, two antemolar teeth being lost: probably the i3 and the p1. The lost incisor is interpreted as i3, because it is the smallest one in those scalopines where it is still present, for example, in Proscapanus and Scalopoides . In the designation of the missing tooth between i2 and p2 as the p1 ( Hutchison 1968: 63) is followed. Based on the alveoles, the i2 was distinctly larger than the i1, both being procumbent. All teeth are heavily worn. The canine is single−rooted, chisel−shaped and slightly inclined anteriorly. The p2–p4 are double−rooted, increasing in size posteriorly. The protoconid of p2 and p3 is centred over the anterior root, a small heel over the posterior one. The p4 is more inflated, the heel a veritable talonid with posterior cuspule. In m1 the talonid is distinctly wider than the trigonid. The oblique cristid extends lingually, but does not join the postero−lingual face of the metaconid. The only cingulid is a short ectocingulid below the hypoflexid. The entostylid is small.

Description of paratypes and referred material

Dentary.—Some other specimens show the alveoli of two incisors, the canine, three premolars, and three molars. The mandibular dental formula is 2i, 1c, 3p, 3m. There is some variability in the position of the mental foramen. In the Petersbuch 6 sample there are four dentaries with the mental foramen preserved. In one specimen there are two foramina, one below the posterior root of p2, the other beneath the posterior root of p4. In three further dentaries a single foramen is situated either beneath the anterior root of p3, or between the roots or under the posterior root of p3. In the Petersbuch 10 sample there is consistently one mental foramen: twice between the roots of p2 and p3, 24 times below the anterior root of p3, thrice between the roots of p3 and five times beneath the posterior root of p3. In the Petersbuch 18 sample there are four dentaries with the mental foramina preserved: one with one foramen between the roots of p4 and another between the roots of p2 and p3, one with the foramina under the anterior root of m1 and beneath p3/p4, respectively, and two dentaries with a single foramen below the posterior root of p4.

Lower dentition.—The i2 has a strong root, a laterally compressed crown with a mesial crest and no cingulids. It is distinctly larger than the canine. The p2 is similar to p3, but smaller. The size relation of the lower molars is consistently m2>m1>m3. In the m1 the trigonid is longer than in the m2, the talonid is distinctly wider than the trigonid. The oblique cristid terminates at the posterior wall of the trigonid well below the trigonid notch. As there is no metacristid the talonid is lingually open. The m2 has a very narrow trigonid, as it is known from Proscapanus . The trigonid is wider than the talonid. The oblique cristid runs lingually to join the marked metacristid; the talonid is lingually closed. There is a prominent precingulid and a weak ectocingulid below the hypoflexid. The entostylid is small. The m3 is distinctly smaller than the m2, has a talonid reduced in width and no entostylid. Maxilla.—Only two anterior fragments and some with one or two teeth are preserved. The two anterior fragments carry the double−rooted P1–P3 and the alveolus of the canine. In one specimen the canine is single−rooted but in the other double−rooted. Lingually to the canine alveolus of each fragment a foramen pierces the palate, probably the fissura palatina. In front of the canine alveolus there is one large incisor alveolus. The anteriormost part is broken. But on this small flake of bone broken off probably have been no incisor alveoli. Thus two incisors are eliminated, which ones cannot be determined. The maxillary dental formula is?1−1−4−3. In one specimen the origin of the zygomatic arch above the metastyle of M2 is preserved; some other fragments show the lacrimal foramen above the anterior root of M1.

Upperdentition.—The antemolar size relation is I>>C~P3> P1>P2. P1–P3 are double−rooted and monocuspulate. The P3 has a small posterior cingulum. The only P4 of the Petersbuch 18 sample has a small protocone and a tiny parastyle, which is rather a small protuberance of the anterior cingulum. In the Petersbuch 10 sample in 15 P4 the parastyle is tiny with some transitions to a projecting parastyle in three specimens. The protocone is conical in 13 P4 and more or less fused with the lingual cingulum in 5 P4. The mesostyle is clearly divided in all molars. Para− and metaconule are hardly individualised in the M1. The preprotocrista is continuous with paracingulum, which joins a more or less projecting parastyle. Postproto− and postmetacrista run parallel to one another, the premetacrista parallel to the anterior margin. The four roots are situated above protocone, paracone, metastyle, and a very small one above and slightly labial to the centre. In the M2 para− and metaconule are somewhat better developed. The parastyle is completely fused with the preparacrista. Neither a para− nor a metacingulum is developed. On the M3 there are no lingual conules and no paracingulum. There are no labial and lingual cingula in the upper molars.

Humerus.—No complete humerus is preserved, but 12 distal fragments and one proximal from Petersbuch 10. The overall morphology and slenderness indicates a moderate stage of fossorial adaptation. The proximal epiphysis is wider than the distal one. The head is directed parallel to the shaft. The brachialis fossa is large but not very deep. The teres tubercle is moderately long and situated close to the pectoral crest. The pectoral tubercle is situated in mid−shaft position. The deltoid process is short. A prominent scalopine ridge runs from the head to the medial side of the lesser tubercle and separates two areas in different planes. The area delimited by pectoral crest, pectoral ridge and greater tubercle is slightly concave. The notch between head and lesser tuberosity is well defined. On the distal epiphysis there is a large olecranon fossa and a somewhat smaller supratrochlear fossa. The trochlea is broad, thus leaving only a narrow notch between trochlea and the fossa for the m. flexor digitorum profundus ligament.

Ulna.—Only the proximal part is preserved. The abductor fossa is deeply excavated. The proximal crest forms a large blade widely separated from the semilunar notch. A prominent processus anconaeus and smaller but distinct coronoid process delimit the well−defined semilunar notch.

Comparisons

Leptoscaptor shows clear scalopine affinities as defined by Hutchison (1968: 58): the enlarged i2, not enlarged p1 and upper canine, moderately to very broad humerus with a moderately deep brachialis fossa. The allocation with any other talpine tribe can be excluded with certainty. Consequently, with few exceptions, we can restrict our comparison to scalopine genera.

The only Recent Old World member of the Scalopini as defined by Hutchison (1968) is Scapanulus oweni Thomas, 1912 , the Kansu mole, which lives in parts of China. It corresponds to Leptoscaptor in dental formula, the number of roots in the P1–P3 and in the divided mesostyles of the upper molars. However, Leptoscaptor differs from this species in: – the absence of a metastylid on m2 and m3,

– the trigonid of the m1, which is not compressed antero−posteriorly,

– the double−rooted p2,

– the small but present parastyle on P4,

– the pectoral tubercle situated more in the midline of the shaft,

– the greater tubercle and head of the humerus not being twisted medially.

No specimen has been seen. The Scapanulus oweni criteria have been concluded from Storch and Qiu (1983: 119) and from Hutchison (1968: figs. 10D, 11).

Proscapanus Gaillard, 1899 (including Alloscapanus Baudelot, 1968 ) from the Early and Middle Miocene of Europe is distinguished from Leptoscaptor in:

– the complete lower and upper dental formula,

– the well−developed metastylids on m2 and m3,

– the more lingual termination of the oblique cristid on m1, – the better−developed cingulids,

– the more robust humerus, which indicates a better fossorial adaptation.

“ Scalopoides” agrarius ( Skoczeń, 1980) from the Ruscinian of Poland and Germany, described by Skoczeń as Scapanulus agrarius and referred to “ Scalopoides ” by Dahlmann (2001), has similar measurements on the humerus (see Dahlmann 2001: table 8; Skoczeń 1980: table 11). However, if we compare the figures of the humeri of S. agrarius ( Dahlmann 2001: fig. 7.4; Skoczeń 1980: pl. 7/4) to those of Leptoscaptor (see Fig. 2H, I ) the latter is distinctly more slender. Furthermore, the Ruscinian species differs from Leptoscaptor in:

– the oblique cristid of m1 and m2 terminating more buccally,

– the absence of a metacristid on m2,

– the undivided mesostyle on M2 and M3,

– the prominent para− and metaconule on M2.

Scalopoides Wilson, 1960 from the Hemingfordian (Middle Miocene) to Clarendonian (Early Pliocene) and the Hemphillian (Late Pliocene) of the United States has a more robust humerus (cf. Hutchison 1968: fig. 55, table 15), thus indicating a more advanced fossorial adaptation. In the dentition it differs from Leptoscaptor in:

– the presence of the i3,

– the well−developed metastylid on m2 and m3,

– the weakly divided mesostyle on the upper molars,

– the better−developed metaconule and metacingulum on M1.

Scapanoscapter Hutchison, 1968 from the Barstovian (Late Miocene) of Oregon is known only from its dentition. In addition to its distinctly bigger size it differs from Leptoscaptor in having:

– a complete lower dentition,

– a not hypertrophied i2,

– lower molars with antero−posteriorly more compressed trigonids.

Domninoides Green, 1956 from the Lower Pliocene in South Dakota and from some Late Miocene sites in North America has a more reduced lower dentition and a more robust humerus (see Green 1956: fig. 4; Hutchison 1968: fig. 68).

cf. Scalopoides sp. from the Middle Miocene of La Grive is represented by a humerus and some additional similar humeri, referred to the genus by Hutchison (1974). This humerus (see Hutchison 1974: figs. 18, 19) is quite similar in slenderness and overall size to the humeri under study. With some reserve we can refer it to Leptoscaptor . However, there are no dental remains in the La Grive fauna similar to those of Leptoscaptor .

Leptoscaptor is readily distinguishable from all living North American scalopines. Parascalops True, 1894 and Scapanus Pomel, 1848 have a complete lower dentition (3i, 1c, 4p, 3m) and single−rooted p1–p3. Furthermore, their broader humeri indicate a distinctly better fossorial adaptation. Scalopus Desmarest, 1804 also has a broader humerus, a greatly reduced dentition and hypsodont teeth.

Yanshuella Storch and Qiu, 1983 from Late Turolian or Ruscinian of Inner Mongolia and from the Hemphillian of Oregon is distinguished from Leptoscaptor in:

– more robust humerus,

– in the presence of three upper and lower incisors,

– in the single−rooted p2,

– the presence of a small metaconid on p4,

– the better developed cingula on all teeth,

– the oblique cristid terminating more buccally on m2 and m3,

– the undivided mesostyle on the upper molars.

Yunoscaptor Storch and Qiu, 1991 from the Late Miocene of the Yunnan Province, China, so far represented by its type species Y.scalprum only, is in fossorial adaptation quite similar to Leptoscaptor . The Chinese genus differs from ours in (cf. Storch and Qiu 1991):

– the larger overall size,

– the complete set of three lower incisors with an enlarged i1,

– the single−rooted p2,

– the higher−crowned lower molars,

– the undivided mesostyles on the upper molars,

– the head of the humerus, which is directed medio−distally.

Mongoloscapter Lopatin, 2002 is a monospecific scaptonychine genus from the Oligocene Shand Gol Formation of the Tatsin Gol locality in Mongolia. Mongoloscapterzhegalloi Lopatin, 2002 is known only from its type, a dentary fragment with m2–m3. This is an extraordinarily poor basis for the designation of a new genus. This specimen differs from Leptoscaptor in (cf. Lopatin 2002):

– its wider m2 and m3 with well−developed metastylid,

– the oblique cristid joining the metacristid.

Van den Hoek Ostende (2001) described the new talpid subfamily Suleimaninae with the only species Suleimania ruemkae Van den Hoek Ostende, 2001 from the Lower Miocene localities Harami, Kilçak, and Keseköy in Anatolia. This species is mainly known from isolated teeth. This large−sized species is distinctive by the loss of the M3 and the loss of the talonid in the m3, a character known from the erinaceines and the dimylid Exoedaenodus . Furthermore, this species differs from Leptoscaptor in:

– the sharp cutting edges of the premolars,

– the inflated cusps of the m1 and M1,

– the presence of a well−developed hypocone in the upper molars.

Hugueneya Van den Hoek Ostende, 1989 is a monospecific species from the Early Miocene of South Germany. The only species H. primitiva ( Hutchison, 1974), in spite of being also a scalopine, cannot be confused with Leptoscaptor . Hugueneya differs from Leptoscaptor in (cf. Hutchison 1974: fig. 21, pl. 39):

– the presence of four lower premolars,

– the more inflated teeth,

– the more prominent metaconule and the more spaced mesostyles of the upper molars,

– the distinctly more robust humerus.

Discussion

Along with Talpa minuta , Leptoscaptor bavaricum represents the most common talpid in the samples of Petersbuch 6, 10, and 18. Petersbuch 10 yielded the most numerous sample of this species and the only one with postcranial bones. Therefore it was chosen as type locality though the dentaries are better preserved in Petersbuch 6 and 18. The association of lower and upper dentition and of the humerus fragments to the dental remains is without alternative and is certainly correct. The ulna fragments match the humerus fragments in size. The only noticeable difference between the three samples is the position of the mental foramen. It is more variable in the smaller samples than in Petersbuch 10. In the size of the teeth there are no significant differences between the three samples even though some specimens of Petersbuch 18 are slightly smaller (P3) or larger (p2) than the corresponding teeth of the Petersbuch 10 sample. In the talpid samples of Petersbuch 6 and 18 there are no postcranial remains left that can be associated with the teeth of Leptoscaptor . There is another species of Leptoscaptor with a somewhat more robust humerus, L. robustior . This species can unambiguously be identified in its type locality Petersbuch 35. As the fissures from Petersbuch 6, 10, and 18 are directly adjacent to one another, they probably all belong to one fissure system and all three fissure fills may result from the same filling process. Consequently, the three samples possibly represent only one population instead of three different ones. This spatial viewpoint argues in favour of an affiliation between the Petersbuch 6 and 18 samples with L.bavaricum . However, the position of the mental foramen is more variable in Petersbuch 6 and especially in Petersbuch 18, as it is characteristic of the Petersbuch 35 sample, which undoubtedly represents L. robustior . Therefore, we cannot exclude with certainty that either Petersbuch 6 or Petersbuch 18 or even both samples represent L.robustior . The fact that two species only can unambiguously be identified by their humeri is not unique to the genus Leptoscaptor . Regarding Paratalpa , an Oligocene to Agenian genus, and Desmanodon , which appeared in Europe in the Orleanian, there are even two different genera that are only distinguishable by their humeri (see discussion in van den Hoek Ostende 1989, Ziegler 1990). However, in talpids the humeri usually allow discrimination to the level of the tribe and the dentition is more distinctive.

Regarding the loss of two lower antemolars, Leptoscaptor is more advanced than the majority of the scalopine genera. Only the living Scalopus from North America has more reduced dentition with single−rooted premolars. For Scapanulus the data are somewhat contradictory. Storch and Qiu (1983: 119) mention the loss of two upper and lower antemolars of questionable homologies. Consequently, the dental formula could be as in Leptoscaptor . Hutchison (1968: 74), in contrast, mentions a complete lower dentition. Gerhard Storch told me that his antemolar count is correct (personal communication, 18th December 2002). Ziegler (1971: 59) gives the same conclusion as Storch and Qiu, referring to the original description by Thomas (1912: 397). Obviously, Hutchison's antemolar count is erroneous.

Concerning the number of roots in the lower premolars, Leptoscaptor is less advanced than all living scalopines. As Scalopus is too specialised in other characteristics and as the other extant species have more complete dentitions, Leptoscaptor cannot be ancestral to any extant genus. Obviously it is a Miocene offshoot that became extinct somewhat later.

Figures

Fig. 2. Leptoscaptor bavaricum gen. et sp. nov., Petersbuch 10. A. Holotype, left dentary with c, p2–m1 and the alveoles of i1–i2, NHMA P10−608.6, in occlusal (A1) and buccal (A2) views; ca. × 10. B. Left dentary with m1–m3, NHMA P10−608.36, buccal view; ca. × 10. C. Left dentary with m1–m3, NHMA P10−608.37, occlusal view; ca. × 10. D. Left maxillary fragment with P1–P3 and the two roots of the canine, NHMA P10−624.1, occlusal view; ca. × 15. E. Left maxillary fragment with P4–M1, NHMA P10−624.3, occlusal view; ca. × 15. F. Left M2, NHMA P10−625D1, occlusal view; ca. × 15. G. Right M3, NHMA P10−625H4, occlusal view; ca. × 15. H. Left humerus, NHMA P10−612, proximal fragment, anterior view; ca. × 7.5. I. Left humerus, P10−610.2, distal fragment, anterior view; ca. × 7.5.