Mustela nivalis Linnaeus 1766
Year: 2024
Type: other
Abstract: Mustela nivalis Linnaeus, 1766 (Fig. 7 B-H) Mustela aff. praenivalis Heller, 1983: 200; fig. 44; pl. 6/1-4, 16-18; table 25. – Groiss 1983: 354; table 48. – Koenigswald & Heinrich 1999: 94. – Ambros 2006: 54. – Rosendahl, Ambros, Hilpert, Hambach, Alt, Knipping, Reisch & Kaulich 2011: 19; table 3/2 Mustela praenivalis Baumann, 2011: 8. REFERRED MATERIAL. — 5 vertebrae, scapula, baculum, 15 canines, isolated P4 and m1, maxilla fragment, 169 hemimandibles (120♂♂, 49 ♀♀), 102 humeri (63♂♂, 37♀♀), 24 ulnae (15 ♂♂, 9♀♀), 21 radii (16 ♂♂, 3 ♀♀), 100 femora (52 ♂♂, 40 ♀♀), 81 tibiae (62 ♂♂, 19 ♀♀), 33 pelvis bones (551/169 - 120 ♂♂, 49 ♀♀). DESCRIPTION The elongated and low mandibular body has a constant lateral thickness for its whole length (Fig. 8). The lower margin is moderately curved and reaches the curvature peak below the m1 level. The symphysis is long and narrow. Two oval-shaped mental foramina are of similar size but are located on different levels. The mesial one is situated higher, below p2 and the distal one are located below the distal root of p3, and on a lower level than the first. Some specimens have a vestigial, longitudinal, lingual furrow of the mandibular body, but the degree of development varies substantially between individuals from weak to moderate. In most individuals this structure is absent. The strong ramus has a shape of rectangular triangle. Its mesial margin rises gently to the top, while the distal margin is almost vertical. The condylar process is massive and short, elongated laterally and inclined slightly downward on the medial side. It is positioned below the teeth row. The angular process is short and is shaped like a rectangular triangle. The deep masseteric fossa has a rounded mesial margin and reaches the m1/m2 boundary. The teeth row is straight in the occlusal view, with only the p2 crown placed at an angle of 30-40o to the rest of the teeth. The distal halves of p3-p4 are oriented disto-buccally. The teeth are positioned loosely to each other, and between them are visible small diastemas (Fig. 8). The elongated and oval p2 is moderately reduced (Figs 8; 9). The two-rooted p3 is low and moderately massive. The protoconid is pushed strongly mesially and almost exactly to the axis of the tooth. The blunt mesial and rounded distal margins have a weak cingulum. The crown bears an elongated, well-developed, distal, cingular projection. The buccal edge is straight, while the lingual one is weakly convex. The two-rooted p4 is an elongated and robust tooth, with a prominent, medially positioned protoconid, which is moderately separated from the surrounding cingulum. Before the protoconid is a crescent, shallow valley. The stronger cingulum is situated on the distal margin. The mesial and distal margins are blunt, while the distal halves of the buccal and lingual edges are strongly convex. This bulge is more developed on the buccal side. The elongated and narrow m1 is moderately trenchant. The crown has a long and low paraconid and prominent, but relatively low protoconid. The trigonid is moderately long and low in relation to tooth length. The buccal margin is moderately convex. The lingual margin of the paraconid and talonid is straight, while the lingual edge of the protoconid is moderately convex. The short and moderately broad talonid bears a centrally positioned hypoconid. The reduced m2 is a moderately large, oval-shaped and one-rooted tooth with a low crown (Figs 8; 9). COMPARISON WITH MUSTELA ERMINEA The morphometric analysis of the material of the smallest mustelids from Hunas was carried out based on the sex division, determined based on the combination of the length m1 and the height of the mandibular body after m1. By comparing with the sexually divided Silesian population of the extant M. nivalis, it was possible to separate the population into ♂♂ and ♀♀. The taxonomic analysis also included a comparison with the sexually divided Silesian population of the extant M. erminea, M. palerminea and M. praenivalis. Both ancient species have already been subjected to critical analysis (Marciszak et al. 2021), which showed that many of the previously reported distinguishing features are no longer valid. For this reason, the legitimacy of their designation was not discussed here, and the focus was on comparing the given characteristics of the Hunas population with other species. In particular, the most important similarities and differences were highlighted, which in the end allowed us to reach a credible conclusion. Compared to M. erminea, cranial and dental material of the smallest mustelids from Hunas show differences in: 1) overall smaller size, well documented by the L m1, where the mean of M. nivalis ♂♂ from Hunas (4.43 mm, 4.02-4.97 mm, n = 103) is distinctly smaller than the mean of both sexes of M. erminea (♂♂ 5.84 mm, 5.51-6.36 mm, n = 151; ♀♀ = 5.19 mm, 4.65-5.57 mm, n = 177), even if slightly overlapping with ♀♀ M. erminea (Table 6); 2) on average shorter and shallower masseteric fossa, reaching maximally the m1/m2 boundary, with a more triangular, mesial margin, although some individuals from Hunas also have a more rounded, mesial margin. Mustela erminea possesses, longer ones on average, reaching m1/2 up to the trigonid/talonid m1 border, and deeper masseteric fossa, for which the mesial margin is almost always rounded; 3) shape of the coronoid process. In M. nivalis from Hunas, the mesial and distal edges of this process are approximately of the same length and form the same angles with the longitudinal axis of the mandible. In M. erminea, the mesial edge is more inclined than the distal one, which is almost vertical and therefore considerably shorter; 4) presence of weakly to moderately marked, but still stronger than in M. erminea, longitudinal, lingual furrow of the mandibular body; 5) proportionally larger and less reduced p2, where p2 L/ m1 L index of M. nivalis from Hunas (♂♂ 28.3, 22.9-31.9, n = 26; ♀♀ 29.4, 26.9-32.0, n = 5) is higher than that of M. erminea (♂♂ 23.1, 20.4-26.7, n = 151; ♀♀ 24.1, 20.5- 27.0, n = 178). There is apparently some overlap, but the ratios differ notably; 6) narrower p3, which is well documented by ratios, but the ranges of variability strongly overlap: M. nivalis from Hunas (♂♂ 56.0, 43.2-69.2, n = 46; ♀♀ 56.0, 46.8-66.4, n = 18) is higher than this of M. erminea (♂♂ 61.5, 54.2-68.7, n = 197; ♀♀ 60.2, 50.7-69.1, n = 230).The morphotype analysis showed variable results in both species, and the higher proportion of more advanced morphotypes in ♂♂. In ♂♂ M. nivalis from Hunas the most common are morphotypes B (43.5%, wider distally than mesially, without a buccal protrusion) and C (37.0%, distally strongly widened and the occlusal crown outline is therefore strongly asymmetrical). For Hunas ♀♀ the more typical morphotypes are A2 (50.0%), distally also not widened, but with a mesio-buccal protrusion of the crown margin, and B (22.2%). Other morphotypes in both sexes of M. nivalis from Hunas are much less common (Table 7). In M. erminea one morphotype is clearly dominant, C (89.3%) in ♂♂ and B (74.3%) in ♀♀ (Table 7); 7) narrower p4, with less marked difference between the mesial and distal halves of the crown, where both the means and the ranges of variability of the Ba/Bp p4 indexes almost do not coincide: M. nivalis from Hunas (♂♂ 88.8, 83.8- 93.7, n = 69; ♀♀ 90.3, 87.2-94.1, n = 29) is higher than that of M. erminea (♂♂ 74.6, 62.2-74.4, n = 248; ♀♀ 81.4, 68.3-85.8, n = 162) (Table 6). The morphotype analysis documented the distinctly wider (in relation to the mesial) distal half of p 4 in M. erminea. In both sexes (♂♂ 94.3%, ♀♀ 82.1%) of this species the most advanced morphotype C dominated, where the crown is strongly widened buccolingually. In M. nivalis from Hunas (♂♂ 81.2%; ♀♀ 75.9%) the most common is morphotype B, where the buccal margin is still almost straight, while the lingual margin in the distal part holds a moderately developed convexity. In the Hunas population there is also the most primitive morphotype A, with a narrow and elongated crown, with the mesial and distal halves of similar width (♂♂ 14.5%; ♀♀ 20.7%) (Table 7); 8) m1 with a proportionally lower and shorter trigonid and longer and broader talonid, where the indexes of trigonid and talonid length and breadth of ♂♂ are higher than ♀♀ in both species, and where both the means and the ranges of variability of L ta/L tr m1 and B ta/B tr m1 indexes almost do not overlap. In M. nivalis from Hunas both ratios are as follows: L ta/L tr m1 (♂♂ 40.6, 30.5-51.2, n = 103; ♀♀ 49.1, 39.2-54.4, n = 39), while B ta/B tr m1 (♂♂ 90.6, 87.1-95.8, n = 103; ♀♀ 91.7, 87.2-96.2, n = 39). The values of both indexes in M. erminea are distinctly lower: L ta/L tr m1 (♂♂ 23.9, 18.6-32.4, n = 151; ♀♀ 27.8, 20.8-33.9, n = 177), while B ta/B tr m1 (♂♂ 78.1, 66.5-87.1, n = 151; ♀♀ 82.9, 77.7-86.1, n = 177) (Table 6); 9) much less developed m1 protoconid broadening, usually, where it is present, occurs in variable size on the lingual margin, while in M. erminea this crown bulging occurs on the buccal and lingual sides. It is well illustrated by the morphotype analysis, where for both sexes of M. erminea (♂♂ 94.7%, ♀♀ 91.5%) the evolutionarily most advanced morphotype D is dominant, broadened buccally and lingually, commonly with a lingual, additional, median root. In M. nivalis from Hunas the situation is totally different and more variable. In ♂♂ morphotype C is dominant (73.8%), only lingually widened, tending to form a lingual root under the metaconid ridge of the protoconid. About one-fourth (24.3%) are of the less advanced morphotype B, which is only buccally widened, and is dominant (48.7%) in ♀♀ M. nivalis from Hunas. There are fewer of morphotype C (18.0%) and the most primitive A (25.6%), with an elongated and narrow crown (Table 7). COMPARISON WITH MUSTELA NIVALIS When comparing M. nivalis from Hunas with the extant Silesian population of this species, we found few distinguishi
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6967901913
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