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Background/Objectives: Scutiger ningshanensis (Fang, 1985) is an endemic Chinese amphibian species within the genus Scutiger (Megophryidae). Despite its ecological significance, its mitochondrial genome architecture and evolutionary relationships remain poorly understood. Given the high structural variability in Megophryidae mitogenomes and unresolved phylogenetic patterns in Scutiger, this study aims to (1) characterize the complete mitogenome of S. ningshanensis, (2) analyze its molecular evolution, and (3) clarify its phylogenetic position and divergence history within Megophryidae. Methods: The complete mitochondrial genome was sequenced and annotated, followed by analyses of nucleotide composition, codon usage bias, and selection pressures (Ka/Ks ratios). Secondary structures of rRNAs and tRNAs were predicted, and phylogenetic relationships were reconstructed using maximum likelihood and Bayesian methods. Divergence times were estimated using molecular clock analysis. Results: The mitogenome of S. ningshanensis is 17,282 bp long, encoding 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and a control region, with a notable AT bias (61.05%) with nucleotide compositions of T (32.51%), C (24.64%), G (14.3%), and A (28.54%). All tRNAs exhibited cloverleaf structures except trnS1, which lacked a DHU stem. Phylogenetic analysis confirmed the monophyly of Scutiger, forming a sister clade to Oreolalax and Leptobrachium, and that S. ningshanensis and S. liubanensis are sister species with a close evolutionary relationship. Positive selection was detected in Atp8 (Ka/Ks > 1), suggesting adaptation to plateau environments, while other PCGs underwent purifying selection (Ka/Ks < 1). Divergence time estimation placed the origin of Megophryidae at~47.97 MYA (Eocene), with S. ningshanensis diverging~32.67 MYA (Oligocene). Conclusions: This study provides the first comprehensive mitogenomic characterization of S. ningshanensis, revealing its evolutionary adaptations and phylogenetic placement. The findings enhance our understanding of Megophryidae’s diversification and offer a genomic foundation for future taxonomic and conservation studies. Full article

Species of the genus Oreolalax displayed crucial morphological characteristics of vertebrates transitioning from aquatic to terrestrial habitats; thus, they can be regarded as a representative vertebrate genus for this landing phenomenon. But the present phylogenetic status of Oreolalax omeimontis has been controversial with morphological and molecular approaches, and specific gene rearrangements were discovered in all six published Oreolalax mitogenomes, which are rarely observed in Archaeobatrachia. Therefore, this study determined the complete mitogenome of O. omeimontis with the aim of identifying its precise phylogenetic position and novel gene arrangement in Archaeobatrachia. Phylogenetic analysis with Bayesian inference and maximum likelihood indicates O. omeimontis is a sister group to O. lichuanensis, which is consistent with previous phylogenetic analysis based on morphological characteristics, but contrasts with other studies using multiple gene fragments. Moreover, although the duplication of trnM occurred in all seven Oreolalax species, the translocation of trnQ and trnM occurred differently in O. omeimontis to the other six, and this unique rearrangement would happen after the speciation of O. omeimontis. In general, this study sheds new light on the phylogenetic relationships and gene rearrangements of Archaeobatrachia. Full article