Mygalea antiqua ( Pomel, 1848 )

Ziegler, Reinhard, 2003, Moles (Talpidae) from the late Middle Miocene of South Germany, Acta Palaeontologica Polonica 48 (4), pp. 617-648 : 619-620

Mygalea antiqua ( Pomel, 1848)

Fig. 1 .

Material and measurements.—Petersbuch 6: NHMA P6−1065/1, left dentary fragment with m1–m3; Lm1–m3 (6.45), h of dentary below m1 (2.80), m1 (2.38×1.17×1.36), m2 (2.32×1.25×1.35), m3 (1.97×1.09×1.02); NHMA P6− 1065/2, left dentary fragment with m3 and complete ascending ramus; h of dentary below m1 (2.70), h1 of coronoid (9.15), h2 of coronoid (7.80), m3 (1.86×1.04×0.95).

Description

Dentary.—The coronoid process, which is slightly bent posteriorly, forms a nearly right angle with the horizontal ramus. The masseteric fossa is moderately deep. The internal temporal fossa is deeply excavated. The mandibular foramen opens directly below the mylohyoid ridge, slightly posterior to the centre of the ascending ramus. The angular process is shovel−shaped with an internal concavity and a crest on the external side. The condylar process lies high above the level of the tooth−row. There are two mental foramina: one between the roots of m1, another beneath p1 or the posterior root of p2. There are 10 alveoles anterior to m1: two for p2–p4 each and one for i1, i2, c and p1 each. Consequently, the mandibular dental formula is 2−1−4−3. According to the alveoles the lower premolars decrease in size anteriorly, the i1 is procumbent.

Lower molars.—The size relation of the lower molars is m1>m2>m3. In the m1 the trigonid is distinctly narrower than the talonid, in the m2 only slightly, in the m3 it is somewhat wider. The protoconid is slightly higher than the hypoconid in the m1, but distinctly higher in m2 and m3. Most conspicuous in the lower molars is the strong cingulid, which extends from below the paraconid to the hypoconid. Postcingulids are somewhat weaker on m1 and m2 and rudimentary on m3. Lingual cingulids are absent. A short entostylid is developed in m1 and m2. The oblique cristid terminates at the posterior wall of the trigonid below the protocristid, slightly lingual to the protocristid notch. In the m2 a faint metacristid is developed.

Discussion

There are three Mygalea species in the Miocene of Europe. Mygaleamagna Ziegler, 1990, the oldest and largest species, is only known from the type locality Budenheim or Hessler from the Calcareous Tertiary in the Mainz Basin. It is correlated with the Lower Miocene (Middle Agenian, MN 2 a). This species has distinctly larger, primarily wider, teeth than the Petersbuch specimens and has the i3 retained .

Mygalea jaegeri ( Seemann, 1938) is mainly known from faunas correlatable with MN 5, e.g., the type locality Viehhausen near Regensburg ( Seemann 1938) and Sandelzhausen ( Ziegler 1990, 2000). This species also has retained its i3 and it is smaller than the specimens under study.

In the evolutionary level, as indicated by the reduced number of lower incisors, both Petersbuch dentaries come closest to Mygalea antiqua from Sansan, where the i3 is lost. The position of the mental foramina is quite variable in the Sansan sample. In four dentaries the following combinations are present: (1) anterior part broken/ below anterior root of m1, (2) below p1 and anterior root of p3, (3) below c and p4/m1, (4) below p1 and p4. Compared to Petersbuch 6, the mental foramina are slightly shifted anteriorly in the Sansan sample. In two dentaries the m1 is larger than the m2, in another it is smaller. However, in overall size the lower molars are larger, mainly wider than ours. In spite of this small size difference, the Petersbuch 6 specimens are considered to represent Mygalea antiqua . This species is also recorded in the Swiss localities Zeglingen, Rümikon and Schwamendingen ( Kälin 1993, all MN 6), and in the German sites Langenau ( Sach and Heizmann 2001, MN 4) and Hambach 6C ( M. cf. antiqua, MN 5/6, Z iegler and Mörs 2000). The Petersbuch 6 sample is the latest record of this species and its genus thus far.

Mygalea is allocated to the Desmaninae by most students except Rümke (1985: 16). She considers the subfamilial allocation not justified, unless the intermediate position of Mygalea can be demonstrated. I think this is not necessary. The humeri of all three Mygalea species are known and show clear desmanine affinities. In the most advanced species, M.antiqua , the i3 is absent. Hence it cannot be ancestral to any extant desmanine. The genus may be a desmanine side branch that became extinct in the early Late Miocene.

Figures

Fig. 1. Mygalea antiqua, Petersbuch 6. A. Left m1–m3, NHMA P6−1065.1, in occlusal (A1) and buccal (A2) views; ca. × 10. B. Left dentary with m3 and complete ascending ramus, NHMA P6−1065.2, buccal view; ca. × 5.