Abstract:[Objectives] In order to clarify taxonomy and molecular phylogenetics of Micromys in China,this study analyzed morphological and molecular data of 9 specimens of M. minutus, 22 specimens of M. erythrotis, and 19 pending specimens of Micromys collected between 2018 and 2021. [Methods] Themorphological characteristics of specimens and skulls were described and measured. Molecular phylogenetic studies include the calculation of genetic distance (the Kimura 2-parameter model) and the construction of phylogenetic trees (maximum likelihood, ML). [Results] The morphological characteristics of pending specimens of Micromys showed differences from M. minutus and M. erythrotis. The back of the body is black-brown (Fig. 1). The base of the hair on the abdomen is gray (Fig. 1). The tip of the hair is gray-white (Fig. 1). The color of the hair on the sides of the body is clearly differentiated (Fig. 1), the dorsal surface of the tail is dark brown (Fig. 1) and the ventral surface of the tail is gray-brown (Fig. 1). Tail length is longer than 120% of head and body length (Table 2). The zygomatic arch is clearly curved inward (Fig. 2). Greatest length of the skull and Condyloincisive length (18.59 ± 0.48 mm and 17.43 ± 0.48 mm) is longer (Table 2). Palatal length (9.35 ± 0.11 mm) is longer (Table 2). Braincase height (7.43 ± 0.06 mm) is higher (Table 2). The genetic distances between pending specimens of Micromys and M. minutus and M. erythrotis are 0.115 and 0.136, which are near the genetic distance (0.126) between M. minutus and M. erythrotis. Based on the complete sequence of the Cyt b of mtDNA and nuclear gene sequences (IRBP1, RAG1, and RAG2), two phylogenetic trees were constructed. Samples were clustered into 3 clades in both phylogenetic trees (M. minutus clade, M. erythrotis clade, and pending specimens of Micromys clade) with high confidence (Fig. 4, 5). [Conclusion] The results of morphological analyses and the molecular phylogenetics supported that the pending specimens of Micromys arean independentspecies, corresponding to M. m. pygmaeus reported in previous studies. Based on the locality, genetic distance, and morphological differentiation, it is suggested that the M. m. pygmaeus should be elevated to a species and named M. pygmaeus comb. nov.. The samples of M. minutus in phylogenetic tree based on the Cyt b of mtDNA were clustered into 6 lineages:Japanese and Korean lineage, European lineage, Novosibirsk Russia lineage, Northeast China and Far East Russia lineage, Anhui China lineage, and Taiwan China lineage.
