Proscapanus sansaniensis ( Lartet, 1851 )

Ziegler, Reinhard, 2003, Moles (Talpidae) from the late Middle Miocene of South Germany, Acta Palaeontologica Polonica 48 (4), pp. 617-648 : 626-629

Proscapanus sansaniensis ( Lartet, 1851)

Fig. 4 .

Material (measurements see Tables 3, 4).— Petersbuch 10: CRW P10−620–621, left dentary fragment with p1–p3, right humerus. Petersbuch 31: NHMA P31−163A1 , 163 C 1, 163E 3, 162B2, 164A1, 2 dentary fragments with teeth, 2 upper teeth, left humerus; CRW P31−163, 164, 4 dentary fragments with teeth, 2 maxilla fragments with teeth, 8 isolated teeth, 6 humeri, 5 ulnae, 3 radii. Petersbuch 35: CRW P35−55, 56, 5 isolated teeth, left humerus, left ulna fragment, right radius. Petersbuch 48: NHMA P48−89A1 +B2, right dentary fragment with teeth, left M1; CRW P48−89, 90, right maxilla fragment with P4, 4 isolated teeth, 4 humeri .

Description

Dentary —Only some more or less complete fragments of the horizontal ramus are preserved. The jaw slightly tapers anteriorly. The dentary fragment from Petersbuch 10 shows mental foramina below p4/m1 and beneath p2. In two specimens from Petersbuch 31 the anterior mental foramen is situated between the roots of p2 and p3, the posterior one under the trigonid of m1. In the dentary fragment from Petersbuch 48 there are three mental foramina, one situated between the roots of p1 and p2, and one below the anterior and posterior root of p4 each. All teeth anterior to p4 are single−rooted. According to their alveoles the three incisors are increasingly inclined anteriorly, i2 being larger than i1 and i3. The canine is only slightly inclined anteriorly.

Lower dentition.—p1 to p3 are slightly inflated and increase in size. There is an incipient anterior crest extending toward the apex of the protoconid. A faint posterior basal cuspule is developed. The p4 is rectangular in occlusal outline and has an antero−buccal and posterior cingulid, the latter culminating in a postero−lingual basal cuspule. The sizes of the molars are ranked in the following order, m2>m1>m3. The oblique cristid extends lingually to join the metacristid. In the m1 the paralophid is curved and leaves a long trigonid, whereas it is very short in m2 and m3. There is a marked precingulid in m2 and m3. In the Petersbuch 31 sample the pre− and ectocingulid of m1 are indistinct, whereas they are better developed in the Petersbuch 48 dentary. In the m1 the talonid is wider than the trigonid, in the m2 the trigonid is somewhat wider and in the m3 distinctly wider than the talonid.

Maxilla.—Two fragments from the Petersbuch 31 sample show the infraorbital foramen above the mesostyle of M1, the anterior opening of the infraorbital canal above the posterior root of M2 and the origin of the zygomatic arch above M3.

Upperdentition.—Only P4 to M3 are preserved. The P4 has an indistinct, hardly projecting parastyle. On the lingual talon there is no vestige of a protocone, but a lingual cingulum. The molars have four roots, the posterior one being the strongest and the central one the weakest. The M1 has a deeply divided mesostyle, a slightly projecting parastyle and indistinct para− and metaconule. The marked paracingulum joins the parastyle; the metacingulum tapers but extends to the postero−labial corner. The M2 also has a divided mesostyle. In some specimens the lingual conules are somewhat better developed than in the M1. Para− and metacingulum are either very thin or even absent. In the M3 the mesostyle is only superficially divided. There are only three M3 from the Petersbuch 31 sample, which are assumed to belong with Proscapanus sansaniensis because of their size. One has a marked paracingulum, in two M3 it is absent.

Postcranial bones —The humerus strongly resembles the specimens from Sansan in all morphological details and in gracility. The brachialis fossa is deeply excavated, the teres tubercle long, the supratrochlear fossa small, and the scalopine ridge marked and shelf−like.

In the ulna the most conspicuous character is the deep abductor fossa, which extends on the proximal moiety of the lateral side. The proximal crest delimits the large area of insertion for the triceps.

The radius has a capitular process projecting proximally. The distal joint is characterised by the large scaphoid articular facet.

Discussion

Proscapanus sansaniensis is based on an anterior fragment of a dentary with the four premolars from Sansan, described by Lartet (1851: 13) as Mygalesansaniensis. Gaillard (1899) described Proscapanussansaniensis and selected as type the humerus from Sansan, once described as Talpasansaniensis by Lartet (1851: 14). Ginsburg (1963) synonymized the type of Mygalesansaniensis with Proscapanussansaniensis. The dentary fragment of Mygalesansaniensis is the valid type by page priority over the lectotype humerus of Talpa sansaniensis . Alloscapanus auscitanensis from Sansan was described by Baudelot (1968). She referred to this species the type of Mygalesansaniensis. As this is not conformable with rules of the International Code of Zoological Nomenclature (for the current edition, see ICZN 1999), Hutchison (1974: 233) synonymized Alloscapanus auscitanensis with Proscapanus sansaniensis . Hutchison (1974) comments upon the somewhat confusing typology of the species in more detail.

The ample material of Sansan is the reference sample of Proscapanus sansaniensis . The Petersbuch specimens fit morphologically well with Proscapanus sansaniensis from the type locality Sansan. In most dentaries from Sansan the anterior mental foramen is situated between p1 and p2, and below p2, the posterior one under the posterior root of p4. In the dentary from Petersbuch 31 the mental foramina are slightly shifted posteriorly. The size differences between the teeth and bones of the Petersbuch samples on the one hand and Sansan sample on the other are more marked. This is not due to sample bias. In some teeth (p4–m2) the length measurements from Petersbuch exceed the size range of the larger sample from Sansan. This means that these teeth are more slender than in Sansan. Only the p1 from Petersbuch 31 is smaller than in the Sansan sample. In Sansan in three dentaries p1>p2, in the type dentary with p1–p4, p1, and p2 have the same length, but p1 is somewhat wider than p2. This means that p1 is enlarged with respect to p2 and p 3 in Sansan, whereas in Petersbuch 31 the size relation is p1<p2<p3<p4. In the upper dentition the size differences are less obvious. Some P4 are wider, some M1 more slender than in the Sansan sample, and the M2 fit reasonably with Sansan. As much as can be concluded from a few measurements, the Petersbuch specimens correspond well in size P. sansaniensis from La Grive (cf. Baudelot 1972: table 13). However, the m1 are also wider in this sample. As there is no clear size trend visible and as there are no mentionable morphological differences, the description of a new species is considered neither necessary nor advisable. Obviously Proscapanus sansaniensis is a species with a large variability in size, as is already evident from the samples of the Upper Freshwater Molasse in South Germany, e.g., Sandelzhausen (cf. Ziegler 2000: fig. 2).

Proscapanus sansaniensis is a species with a wide temporo−spatial distribution. It is recorded from Germany, Switzerland and France, from sites correlative with MN 4 (Vieux Collonges, Mein 1958) to MN 9 (Nebelbergweg, Kälin and Engesser 2001). The northernmost occurrence is from Hambach in the Lower Rhine Embayment ( Ziegler and Mörs 2000).

Figures

Fig. 4. Proscapanussansaniensis. A. Left dentary fragment with canine root and p1–p4, Petersbuch 31, NHMA P31−163A1, occlusal view; ca. × 10. B. Right m1–m3, Petersbuch 31, NHMA P31−163B2, occlusal view; ca. × 10. C. Right dentary fragment with p4–m2, Petersbuch 48, NHMA P48−89A1, buccal view; ca. × 10. D. Left P4, Petersbuch 31, NHMA P31−163C1, occlusal view; ca. × 10. E. Left M1, Petersbuch 48, NHMA P48−89B2, occlusal view; ca. × 10. F. Right M2, Petersbuch 31, NHMA P31−163E3, occlusal view; ca. × 10. G. Left humerus, Petersbuch 31, NHMA P31−164A1, anterior view; ca. × 5.