Mustela eversmanii (Leeson, 1827)

Marciszak, A, Stefaniak, K & Gornig, W, 2017, Large mammals (carnivores, artiodactyls) from Solna Jama Cave (Bystrzyckie Mts, Southwestern Poland) in the context of faunal changes in the postglacial period of Central Europe, Palaeontologia Electronica (Bellingham, Wash.) 11 (4), pp. 1-37 : 13-15

Mustela eversmanii (Leeson, 1827)

Figures 9-10

Specimens. Body mandible without ramus, with present p2-m1 (JSJ/Mev/1).

Measurements. Mandible (JSJ/Mev/1): 4, 29.85 mm; 5, 26.09 mm; 6, 10.82 mm; 7, 12.00 mm; 8, 4.11 mm; 12, 11.02 mm; 13, 5.49 mm; 14, 10.20 mm; 15, 5.29 mm; 18, 16.15 mm; 19, 8.53 mm; p2- L, 2.82 mm; p2-B, 1.68 mm; p3-L, 4.86 mm; p3-Bp, 2.32 mm; p4-L, 5.12 mm; p4-Ba, 2.08 mm; p4-Bp, 2.96 mm; m1-L, 9.78 mm; m1-L-tri, 7.41 mm; m1- L-tal, 2.24 mm; m1-B-tri, 3.98 mm; m1-B-tal, 2.32 mm; m2-L, 1.34 mm. See Appendix 4 for measured parts.

Description and comparisons. The taxonomy of mustelids, animals of great sex-related, geographical and individual variation, is in many cases still incompletely resolved. Even when well preserved, the specimens are usually difficult to identify, especially when only a single individual is available from the locality. This was the case of the specimen from Solna Jama Cave — right mandible of a fairly large mustelid. The general shape and size clearly indicate a polecat and simultaneously exclude other related taxa like mink or marten. The large size and advanced dental morphology exclude also Mustela stromeri Kormos, 1934 ( Kormos, 1934; Marciszak, 2012). At present, two polecat species occur in Poland: Mu. eversmanii and Mu. putorius Linnaeus, 1758 ( Wolsan, 1993). Although similar in the morphometric and morphological characters, they differ in many features, which were intensively studied. The most distinctive characters are those of calvarium, but also mandible offers some reliable traits, all of them expressed as ratios. The direct measurements are not useful when determining species of the subgenus Putorius . Mustela eversmanii is on average larger, the mean values of both species are different, but the extreme values are almost the same. The most reliable mandible features are the relative size of c1, p2 and m2, size and shape of masseter fossa as well as symphysis and mandibular body robustness ( Wolsan, 1993; Marciszak, 2012). The specimen lacks c1 and m2, but the size of teeth can be estimated based on alveola measurements. Alveola c1 seems to be large and massive, while m2 alveolar length (1.34 mm) suggests that the tooth was proportionally very small and narrow. The p2 is also

MARCISZAK, GORNIG, & STEFANIAK: MAMMALS FROM SOLNA JAMA CAVE reduced and two-rooted, and is comparatively smaller than the average p2 of Mu. putorius .

The mandible morphology of the specimen also clearly indicates Mustela eversmanii ( Figure 9 ). The mandible body is high and thick, but apparently shorter than in Mu. putorius . In lateral buccal view is very bulky, the lower margin is strongly convex, instead of being curved gently as in Mu. putorius , and the maximum of the curve is located under m1 paraconid. The ratio of m1 total length to mandible body height measured between p4 and m1 (measurement no. 14) is very useful in species identification. Its mean value for Mu. eversmanii is 92 (N = 102), while for Mu. putorius the mean is 110 (N = 332). The specimen with its ratio of 95.9 is much closer to the eversmanii than to the putorius mean, and the data show a non-characteristic intermediate value ( Figure 9 ). Even the direct measurement no. 14 is quite useful, and most authors agree that values below 8.0 mm indicate Mu. putorius with high probability. Similarly, the mandible body higher than 9.0– 9.5 mm allows to classify the specimen as Mu. eversmanii . However, research on a large sample of both species showed that the measurement was also correlated with individual age and variation, and some huge individuals with comparatively not very high mandible body are also known ( Marciszak, 2012). In the examined mandible the masseter fossa is anteriorly rounded and centrally deep, and reaches the m1/m2 border. A circular depression occurs on the labial side below the protoconid of m1, while this character is poorly developed in Mu. putorius . On the lingual side it displays ridge-like thickenings along the tooth row, and elongate depressions occur below it. The lingual wall of the mandible body in Mu. putorius is rather uniform in shape, without such structures. The mandible from Solna Jama Cave is very different in the stoutness of its symphysal part from that if Mu. putorius , and very similar to that of Mu. eversmanii . The anterior part of the mandible forms a massive and elongated symphysis, in proportion to the large size of the canine alveole. The posterior boundary of the masseter fossa in Mu. putorius is more rounded and not produced so far anteriorly as in Mu. eversmanii , where it often extends below the trigonid/talonid border, and terminates in an acute angle. Finally, the inferior swelling of the ramus below the masseter fossa in labial view is visible, though only a fragment is preserved. The tooth wear indicates an old individual, and combined with the size indicates a senile, medium-sized male ( Figure 10 ).

Remarks. This mustelid is regarded as a highly specialised big rodent hunter ( Heptner and Naumov, 1967; Sickenberg, 1968), whose strong asso-

PALAEO- ELECTRONICA.ORG ciation with large, steppe rodents from genus Spermophilus , Cricetus or Gerbillus , was observed in many regions, also Poland ( Buchalczyk and Ruprecht, 1975; Kurtén, 1968; Wolsan, 1993; Šálek et al., 2013). The same association was documented in many late middle and late Pleistocene sites, where the same layers held remains of Mustela eversmanii and those large, steppe rodents ( Kurtén, 1968; Sickenberg, 1968; Marciszak, 2012). In Solna Jama Cave there is no evidence for such association. However, their absence does not necessarily mean that these rodents were not available to the steppe polecat in the environs of the cave. It is very likely that the fossil record from the site is incomplete, since much deposit remains to be excavated.

Although rodents of the genus Spermophilus are the main prey for this species in many regions, they are not indispensable to the polecat. Their presence or absence in particular areas need not be a crucial for the Mustela eversmanii existence. In many regions local populations subsist on different prey, like rodents from genus Cricetus and Microtus in Hungary ( Lanszki and Heltai, 2007), Rhombomys opimus (Lichtenstein, 1823) in Kazakhstan ( Heptner and Naumov, 1967) and members of the genus Ochotona Link, 1795 and Microtus as well as family Spalacidae Gray, 1821 in China ( Li et al., 2012). In areas where, like for example in southeastern Poland, populations of Spermophilus suslicus ( Güldenstaedt, 1770) have decreased dramatically in the last 50 years, Cricetus cricetus seems to be one of the most important prey items. Based on the fossil assemblage, it is probable that the late Pleistocene Mu. eversmanii in Poland hunted mainly Lemmus lemmus , Dicrostonyx gulielmi , Clethrionomys glareolus , Microtus agrestis , Mi. arvalis and Mi. gregalis ( Marciszak, 2012; Krajcarz et al., 2014b). Remains of some of these rodents where also found in Solna Jama Cave.

This is the first record of Mustela eversmanii from the Sudeten caves, and one of the few from the Polish Pleistocene. The oldest Pleistocene record, dated as MIS 10-9, comes from the lowermost layers 19ad from Biśnik Cave, where a small, primitive Mu. eversmanii was found. The species is present in the Eemian sediments of Biśnik Cave (layer 13), where it also occurs in layers dated as the late Pleistocene ( Marciszak et al., 2011; Marciszak, 2012). Apart from these sites, Mu. eversmanii was only found in layer 15/ 12 in Obłazowa Cave (MIS 3) ( Marciszak, 2012) and layer C of Stajnia Cave. Finally, recently Krajcarz et al (2014b) described in detail a left mandible of a modernsized male from layer B2 of Deszczowa Cave. Earlier excavations in Deszczowa Cave ( Cyrek et al., 2000), layer 7, yielded a still undescribed left mandible and three long bones of a great male. These six sites are till now the only confirmed paleontological Polish records of the species. The individual mentioned from Cave no. 4 on Birów Hill ( Muzolf et al., 2009), after detailed morphometric and morphological analysis, proved to be an atypical specimen of Mu. putorius ( Marciszak, 2012) .

Also, the history of recent distribution of the species is poorly documented. The individuals which occur in Southeast Poland have spread from the main Ukrainian population, which is represented by the nominate subspecies Mustela eversmanii eversmanii ( Wolsan, 1993) . The present boundaries of Poland were established after World War II, and until the 1970s Mu. eversmanii was not recorded inside the territory of Poland. Also in the past, none of the researchers ( Gloger, 1833; Pax, 1925) who studied the Silesian fauna mentioned the presence of the species north of the Sudeten arch ( Kostroň, 1948). Although some authors suggested its possible occurrence in Southeast Poland, it is absent in the faunal list ( Buchalczyk, 1964). In the 1970s and 1980s the species was recorded from Southeast Poland several times ( Buchalczyk and Ruprecht, 1975; Ruprecht, 1985; Głowaciński and Profus, 1987). Now very little is known about the present status of the species. It is regarded as near threatened in the Polish Red List, but during the last 25 years there were no reliable records. However, the most recent paper on Mu. eversmanii status in Europe lists the species as appearing sporadically in few xerothermic patches ( Šálek et al., 2013).

Figures

FIGURE 9. Right mandible of Mustela eversmanii (JSJ/Mev/1) from Solna Jama Cave. Note relatively short and robust body mandible and massiveness of the symphysal area. Scale bar equals 10 mm.

FIGURE 10. Scatter diagram showing the ratio of mandiblar height (measured after m1) to m1 length in fossil and extant Mustela eversmanii and Mu. putorius. Data from Marciszak (2012) and references therein.