SORICINAE, Fischer, 1814

Van Den Hoek Ostende, Lars W., Casanovas-Vilar, Isaac & Furió, Marc, 2020, Stuck in the middle. A geographical appraisal of the oldest insectivores - and a marsupial - from the Vallès-Penedès Basin (early Miocene, Catalonia, Spain), Comptes Rendus Palevol 19 (1), pp. 1-25 : 19-20

SORICINAE gen. et sp. indet.

( Fig. 5 S-U)

MATERIAL AND MEASUREMENTS (in cm). — Spain. El Canyet , 1 I1 sin., IPS85553 , 1.81 × 075 × 1.30; 2 i1 dext., IPS85552 , –, IPS85555 , 3.20; 2 i1 sin., IPS85554 , 3.60, IPS85556 , –,> 2.94; 1 mandible with i1 and p4 sin., IPS85557 , i1 3.35, p4 1.27 × 0.90); 1 mandible with i1 and m1 dext., IPS20979 , i1 3.18, m1 1.55 × 0.88 × 0.98; 1 p4 sin., IPS85550 , 1.20 × 0.82; 1 mandible with a1- m1 sin., IPS85551 , 0.81 × 0.65, 1.10 × 0.79, 1.54 × 0.86 × 0.98 .

DESCRIPTION

I1

The upper incisor is not fissident, but there is a medial cuspule visible in dorsal view. The dorsal margin is regularly curved. The talon is not much developed. There is a narrow cingulum covering the base of the tooth. The root is only somewhat shorter than the crown.

Mandible

The mandible shows that the mental foramen is placed below the reentrant valley of the m1. It is also noteworthy that the i1 extends back labially as much as below the paraconid of the m1.

i1

The lower incisor is bicuspulate. The anterior tip and the posterior cuspule have a similar height, whereas the intermediate one is a bit lower.

a1

The antemolar has a heart-shaped occlusal outline. It is smaller in size than its posterior counterpart, the p4. There is no posterolingual basin, but it has a tetrahedral morphology.

p4

The last antemolar has a heart-shaped occlusal outline and a ‘paralophid-like’ cristid, which defines a lingual valley.

m1

The most significant characters are the presence of a high entoconid and its corresponding cristid, the oblique cristid ending much labially and a continuous cingulid covering all the base of the tooth, also by the lingual side. The rest of the characters (or their ‘absence’) are detailed in the discussion about the taxonomic ascription.

REMARKS

Surprisingly, this species does not show the typical characters of the Crocidosoricinae , which were the dominant shrews during the early Miocene. Instead, the elements recovered have typical derived Soricinae traits. This is something unusual in localities of this age, as red-toothed shrews become frequent in Eurasia at the end of the Miocene. Some anterior teeth are isolated elements which have been tentatively ascribed to this form because they all come from the same locality, and their general aspect fits well with those of the limited dental series recovered. The two specimens with m1 show that this element is larger than in the rest.

The most significant derived features are the presence of only two lower antemolars (including the p4), a mental foramen placed under the reentrant valley of m1 and a p4 with a posterolingual basin (instead of a two-branched protoconid). If not a soricine shrew in itself, this form could be also ascribed to one of those species purportedly leading to the Soricinae clade (according to Furió et al. 2007), like Carposorex sylviae . Actually, the dimensions of the m1 match perfectly with that species, according to the data provided by Crochet (1975). Moreover, the teeth have a massive aspect, the p4 has a labial branch more developed than the lingual one, and the m1 has a developed entoconid. However, the position of the mental foramen (under the reentrant valley of the m1; more advanced in crocidosoricines, also in Carposorex , in which it is placed under the p4), the absence of any connection between posterolabial crest of the protoconid and the labial cingulid, and the smooth enamel (instead of wrinkled as expected for the genus) discards such generic and specific allocation. In the other known species of the genus, Carposorex burkarti described by Hugueney et al. (2012), the differences are even more, because of the higher number of lower antemolars (at least three in C. sylviae ) and the smaller size.

The oldest representative of the subfamily Soricinae in Europe is Hemisorex robustus . This species has been described in the French sites of Vieux-Collonges, Sansan and La Grive L3, L7 and M ( Baudelot 1967; Engesser 1972, 2009; Hugueney et al. 2012). In fact, the measurements of the m 1 in this form also fit quite well within the ranges provided by Engesser (2009) and Hugueney et al. (2012), with a length of about 1.50 mm and a width a bit less than 1.00 mm. The massive aspect, the bicuspulate i1, the p4 with a posterolingual basin and the position of the mental foramen would also support such ascription. However, the occlusal outline of the m1 (not as much rectangular as in Hemisorex ) and the entoconid cristids (more developed than in Hemisorex ), make a difference.

Paenesorex bicuspis from Petersbuch 31 described byZiegler (2003) could be another possible candidate.However, it differs from the species found in El Canyet in the presence of a vestigial a2 between a1 and p4. Moreover, the overall size of teeth in Paenesorex is smaller than that of this undetermined soricid.

As there is hitherto no soricid species described in the early or middle Miocene matching all these characters, and in the absence of sufficient material we refrain from describing a new species, the most sensible option is leaving the identification of this form as Soricinae indet.