Meles meles (Linnaeus, 1758)

Rosas, Antonio, Soler-Fajardo, Ana, Garcia-Tabernero, Antonio, Huguet, Rosa, Vallverdú, Josep, Fidalgo, Darío, Galli, Emilia & Piñero, Pedro, 2023, 2 D Geometric morphometrics of the first lower molar of the genus Meles Brisson, 1762 including new badger evidence from the Lower Pleistocene Quibas site (Murcia, Spain), Comptes Rendus Palevol 22 (7), pp. 91-107 : 96-99

Meles meles (Linnaeus, 1758)

LOCALITY. — Sierra de Quibas.

AGE. — 1 Ma ( Piñero et al. 2020).

MATERIAL. — Q’18/QS4-1/P19/10 ( Fig. 1), fragmentary right hemimandible, comprising a complete m1.

DESCRIPTION

It is a fragmentary right hemimandible with alveoli for c (canine), p2-p4 (second to the fourth premolar), and m2 (second molar), and a complete m1 ( Fig. 1). It belongs to a young adult, as shown by the small worn area over the cuspids of the m1, and the mild scars of the muscles masseter pars superficialis and pars profunda over the cranioventral part of the masseteric fossa. The coronoid process is missing and the angular process is broken. The horizontal ramus is dorsoventrally short. The alveolus for the c is distally broken, making it impossible to confirm the presence of the p1 (first premolar) alveolus. Both p2-p3 (third premolar) alveoli are buccolingually turned, indicating a shorter teeth row, and a shortening of the mandible. The m1 (maximum length = 18.6 mm; maximum width = 8.5 mm) has a typical M. meles morphology, comprising a longer talonid compared with the trigonid. The protoconid is the tallest cuspid of the trigonid, the paraconid, and the metaconid having similar heights. The metaconid is well developed and is buccolingually broad. The maximum width of the teeth is located at the hypoconid-entoconid level. Both cuspids are well developed, the hypoconid being the largest one. The talonid’s valley is mesiodistally long and shallow. There is a well-developed hypoconulid (buccal) and entoconulid (lingual). A post entoconid cuspid is located in the most distal part of the tooth, closing the talonid. The alveolus of the m2 indicates the presence of a regular m2. The preserved portion of the masseteric fossa is shallow.

CENTROID SIZE (CS) ANALYSIS

The size analysis shows that the Quibas specimen is one of the largest specimens from the sample, being out of the confidence interval for the CS of both current and fossil M. meles , being even larger than M. meles atavus and the rest of the fossils ( Table 2 ; Fig. 3).

Using the Meles meles sample, we also did a Kolmogorov-Smirnov test to study the normality of the sample. After rejecting the normality of the sample (K-S test; p<0.05), we carried out a Mann-Whitney test to test for size differences, finding that the current M. meles sample presented statistically larger values than the fossil M. meles sample (U: 148; z: 2.25; p: 0.02).

ALLOMETRIC ANALYSIS

The variation of size and shape shows a statistically significant but slight association between both variables, both for the current (r2 = 0.02) and fossil M. meles (r2 = 0.14). It is interesting to note that the size variation is larger in the fossil M. meles than in the current ones. In addition, it is observed that the allometric trajectory between both is parallel, presenting identical slopes (0.0002) but different intercepts ( Fig. 4).

MEAN COMPARISONS AND PERMUTATIONS TEST

We compared the mean of the extant M. meles with the means of the remaining M. meles : M. meles fossils, M. meles atavus , and the Meles from the Quibas site. Our results show that the Meles from Quibas were not significantly different from the extant M. meles , but the M. meles fossil group and the group of M. meles atavus were statistically significant, despite having a smaller Procrustes distance compared to the current M. meles ( Table 3 ).

PRINCIPAL COMPONENT ANALYSIS (PCA,

SEE Appendix 2 FOR MORE INFORMATION)

The projection of PC1 vs PC2 (40.65 % of variability; Fig. 5) shows that the negative scores of PC1 (28.23 % of variability), where M. leucurus and Arctonyx albogularis plot, represent a trend of slender m1 that are buccolingually narrow, with a trigonid and talonid about the same length. They also have a wide space between the cusps of paraconid, protoconid, and metaconid, and reduced space between the cuspids of the entoconulid and hypoconulid to the mesial-most point of the tooth. In the positive scores, we observe the reverse trend, with a more robust morphology of m1 caused by quadrangular talonid and a shortened trigonid. This also causes a re-arrangement of the cuspids, since the talonid cuspids are far from the mesial-most point and the trigonid cusps are closer to each other. Regarding the extinct specimens, most of them (including the Quibas one) fall into the variability of Meles , but it is possible to observe a trend in which most of them fall at the more negative part of the distribution, as in more slender morphologies.

The PC2 (12.42% of variability; Fig. 5) distinguishes less between groups or species. In the negative-most end of the axis, we observe a robust morphology, teeth with a globular shape, in which the trigonid and talonid are about the same length, with little separation of the cusps between the metaconid, entoconid, and entoconulid to the lingual edge, in contrast to the wide separation of hypoconid, hypoconulid, and protoconid to the buccal edge. On the other hand, at the opposite end of the axis (positive scores), we find teeth of elongated morphology, with talonid of larger length than the trigonid. Regarding the separation of the cuspids and the edges of the tooth, we observed a wide separation between metaconid, entoconid, and entoconulid to the lingual, and a close location of the hypoconid, hypoconulid, protoconid, and paraconid to the buccal edge. Also, we can observe a greater amplitude in the distal area of the tooth due to the separation between entoconulid and hypoconulid and the distal point of the tooth. Regarding the fossils, M. leucurus and A. albogularis fall in the positive scores, linked to slender morphologies, but a fair amount of extant M. meles fall as well ( Fig. 5). The different fossils are spread along the variability in PC2, but it could be important to mention that M. meles atavus falls at the upper extreme of the M. meles variability, characterized by a slender morphology, as in the case of M. leucurus and A. albogularis . However, other species such as M. magnus , M. thorali , or M. teihardi fall at the opposite extreme of the variability, thus having a more robust (quadrangular-shaped) morphology.

CLUSTERS UPGMA

We did two different clusters using the UPGMA analysis, the first one (UPGMA1; Fig. 6) using all the shape variation comprised by all the different PCs, and the second one (UPGMA2; Fig. 7) also adding the CS to the shape variation. When the size is included, we observe a large cophenetic correlation (0.88), and large values for the different nodes associations (>67). In this UPGMA1 we can see two separated branches, one containing the Asiatic species except for M. magnus and the other one with all of the European species plus M. magnus . These results show us that size has a great influence on the relationships of this cluster because the first branch comprises the groups with smaller teeth and the second one the groups with larger teeth, as demonstrated also by the previously shown CS. This way we can also observe a tendency in the European groups of larger teeth compared to the majority of Asiatic groups.

In the cluster UPGMA2, where only shape information is included, we can see that even slightly lower cophenetic correlation (0.78) compared to the UPGMA1. Also, the nodes associations are weaker than in the previous case, showing that size is an important driving factor for the associations. In this cluster, we observed two different branches: one including only the genus Arctonyx and the other one with all the Meles species. The Meles branch is also divided into two branches, being M. chiai in a different branch and leaving the rest of Meles divided into another two branches. The first branch groups all Asiatic fossils together, including the M. thorali , and the second branch with all the current specimens grouped with the rest of the European fossils. The Meles fossil from the Quibas site is grouped in a branch with the M. meles fossils.