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As a small order of Pterygota (Insecta), Ephemeroptera has almost 3,500 species around the world. Ephemerellidae is a widely distributed common group of Ephemeroptera. However, the relationship among Ephemerellidae, Vietnamellidae and Teloganellidae is still in dispute. In this study, we sequenced six complete mitogenomes of three genera from Ephemerellidae (Insecta: Ephemeroptera): Ephemerella sp. Yunnan-2018, Serratella zapekinae , Serratella sp. Yunnan-2018, Serratella sp. Liaoning-2019, Torleya grandipennis and T. tumiforceps . These mitogenomes were employed to reveal controversial phylogenetic relationships among the Ephemeroptera, with emphasis on the phylogenetic relationships among Ephemerellidae. The lengths of the six mayfly mitogenomes ranged from 15,134 bp to 15,703 bp. Four mitogenomes of Ephemerella sp. Yunnan-2018, Serratella zapekinae , Serratella sp. Yunnan-2018 and Serratella sp. Liaoning-2019 had 22 tRNAs including an inversion and translocation of trnI . By contrast, the mitogenomes of T. tumiforceps and T. grandipennis had 24 tRNAs due to an extra two copies of inversion and translocation of trnI . Within the family Ephemerellidae, disparate gene rearrangement occurred in the mitogenomes of different genera: one copy of inversion and translocation trnI in the genera Ephemerella and Serratella , and three repeat copies of inversion and translocation of trnI in the genus Torleya . A large non-coding region (≥200 bp) between trnS1 (AGN) and trnE was detected in T. grandipennis and T. tumiforceps . Among the phylogenetic relationship of the Ephemeroptera, the monophyly of almost all families except Siphlonuridae was supported by BI and ML analyses. The phylogenetic results indicated that Ephemerellidae was the sister clade to Vietnamellidae whereas Teloganellidae was not a sister clade of Ephemerellidae and Vietnamellidae., Competing Interests: Kenneth B. Storey and Jia-Yong Zhang are Academic Editors for PeerJ., (©2020 Xu et al.)

The family Pyxicephalidae including two subfamilies (Cacosterninae and Pyxicephalinae) is an ecologically important group of frogs distributed in sub-Saharan Africa. However, its phylogenetic position among the Anura has remained uncertain. The present study determined the complete mitochondrial genome sequence of Pyxicephalus adspersus , the first representative mitochondrial genome from the Pyxicephalinae, and reconstructed the phylogenetic relationships within Ranoidae using 10 mitochondrial protein-coding genes of 59 frog species. The P. adspersus mitochondrial genome showed major gene rearrangement and an exceptionally long length that is not shared with other Ranoidae species. The genome is 24,317 bp in length, and contains 15 protein-coding genes (including extra COX3 and Cyt b genes), four rRNA genes (including extra 12S rRNA and 16S rRNA genes), 29 tRNA genes (including extra tRNA Leu ( UAG ) , tRNA Leu ( UUR ) , tRNA Thr , tRNA Pro , tRNA Phe , tRNA Val , tRNA Gln genes) and two control regions (CRs). The Dimer-Mitogenome and Tandem duplication and random loss models were used to explain these gene arrangements. Finally, both Bayesian inference and maximum likelihood analyses supported the conclusion that Pyxicephalidae was monophyletic and that Pyxicephalidae was the sister clade of (Petropedetidae + Ptychadenidae)., Competing Interests: Kenneth B. Storey is an Academic Editor for PeerJ. Jia-Yong Zhang is an Academic Editor for PeerJ.

The owlflies (Family Ascalaphidae) belong to the Neuroptera but are often mistaken as dragonflies because of morphological characters. To date, only three mitochondrial genomes of Ascalaphidae, namely Libelloides macaronius ; Ascaloptynx appendiculatus ; Ascalohybris subjacens , are published in GenBank, meaning that they are greatly under-represented in comparison with the 430 described species reported in this family. In this study, we sequenced and described the complete mitochondrial genome of Suhpalacsa longialata (Neuroptera, Ascalaphidae). The total length of the S. longialata mitogenome was 15,911 bp, which is the longest known to date among the available family members of Ascalaphidae. However, the size of each gene was similar to the other three Ascalaphidae species. The S. longialata mitogenome included a transposition of tRNA Cys and tRNA Trp genes and formed an unusual gene arrangement tRNA Cys -tRNA Trp -tRNA Tyr (CWY). It is likely that the transposition occurred by a duplication of both genes followed by random loss of partial duplicated genes. The nucleotide composition of the S. longialata mitogenome was as follows: A = 41.0%, T = 33.8%, C = 15.5%, G = 9.7%. Both Bayesian inference and ML analyses strongly supported S. longialata as a sister clade to ( Ascalohybris subjacens + L. macaronius ), and indicated that Ascalaphidae is not monophyletic., Competing Interests: Kenneth B. Storey is an Academic Editor for PeerJ.