DOI: 10.3897/vz.75.e153115

Authors: Anna A. Bannikova, Paulina D. Jenkins, Vladimir S. Lebedev, Svetlana V. Pavlova, Vasily D. Yakushov, Alexandra A. Raspopova, Yongke Zhu, Yun Fang, Yue-Hua Sun, Boris I. Sheftel

Abstract: Abstract The taxonomy of the stripe-backed shrew complex (Sorex cylindricauda species group), distributed in mountains of western China, appears challenging due to remarkable variation in morphological traits and relatively recent times of diversification. According to classical points of view only two or three species of the stripe-backed shrews can be distinguished. However, previous molecular reconstructions revealed at least 14 genetic lineages including a number of undescribed cryptic species. In the current study we revise the taxonomic status of large-sized stripe-backed shrews occurring in high mountain areas in south Gansu, north-western Sichuan and western Qinghai that were previously treated as S. aff. cylindricauda or S. sinalis. The available molecular data place them in a separate species-level lineage of the stripe-backed shrew complex. Our morphological analysis indicate that shrews of this lineage are distinct from the two other large-sized Chinese species, S. cylindricauda and S. sinalis, based on both cranial and external traits. Therefore, we here describe it as a species new to science, the karyotype of which is characterized by 2n = 26 with an additional B chromosome and NFa = 44. Our molecular phylogenetic analysis demonstrates multiple instances of mitonuclear discordance among lineages within the S. cylindricauda complex, which is likely a result of mtDNA introgression, thus highlighting the important role of reticulation events in the evolution of the group.

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DOI: 10.3897/vz.72.e90840

Authors: Wolfgang Maier, Adrian Tröscher, Irina Ruf

Abstract: Modern phylogenetics place the Soricidae (shrews) into the order Lipotyphla, which belongs to the relatively new superorder clade Laurasiatheria. Their most derived skull feature is the unusual position and shape of the jaw articulation: Whereas in all other mammals the glenoid region of the squamosum is more or less tightly attached to the otic capsule or petrosal, respectively, in the soricids it is attached to the nasal capsule. This new position of the jaw articulation becomes possible by the posterior extension of the nasal capsule and the rostral shift of the glenoid fossa. By the study of dated postnatal ontogenetic stages of Crocidura russula and Sorex araneus, we show that the glenoid part of the squamosal becomes fixed to the nasal capsule by the ossified alae orbitalis and temporalis. The ala orbitalis is displaced laterally by the expanded cupula nasi posterior; this posterior expansion is well documented by the lamina terminalis, which incorporates parts of the palatinum and alisphenoid. Both alae consist largely of ‘Zuwachsknochen’ (‘appositional bone’) and are then named orbitosphenoid and alisphenoid. By the forward move of the pars glenoidea and of the alisphenoid, the foramen lacerum medium (‘fenestra piriformis’) also expands rostrally. Functionally, the forward shift of the jaw joint helps to keep the incisal biting force high. Biomechanically the jaws can be considered as a tweezer, and the rostral position of the jaw joints makes the interorbital pillar and the shell-like walls of the facial skull a lever for the highly specialized incisal dentition.

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