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Mayflies of the family Neoephemeridae are widespread in the Holarctic and Oriental regions, and its phylogenetic position is still unstable in the group Furcatergalia (mayflies with fringed gills). In the present study, we determined the complete mitogenomes of two species, namely Potamanthellus edmundsi and Pulchephemera projecta, of this family. The lengths of two mitogenomes were 15,274 bp and 16,031 bp with an A + T content of 73.38% and 73.07%, respectively. Two neoephemerid mitogenomes had a similar gene size, base composition, and codon usage of protein-coding genes (PCGs), and the sequenced gene arrangements were consistent with the putative ancestral insect mitogenomes as understood today. The most variable gene of Furcatergalia mitogenomes was ND2, while the most conserved gene was COI. Meanwhile, the analysis of selection pressures showed that ND6 and ATP8 exhibited a relaxed purifying selection, and COI was under the strongest purifying selection. Phylogenetic trees reconstructed based on two concatenated nucleotide datasets using both maximum likelihood (ML) and Bayesian inference (BI) estimations yielded robust identical topologies. These results corroborated the monophyly of seven studied families and supported the family Leptophlebiidae as being of the basal lineage of Furcatergalia. Additionally, the sister-group relationship of Caenidae and Neoephemeridae was well supported. Methodologically, our present study provides a general reference for future phylogenetic studies of Ephemeroptera at the mitogenome level. Full article

The newly collected imaginal materials of the species Neoephemera projecta Zhou and Zheng, 2001 from Southwestern China, which is linking the other genera of the family Neoephemeridae, are described in detail. Nymphs are also photographed for the first time. The morphology of this species shows some characters of the other genera in Neoephemeridae and several autapomorphies. However, most characters can be seen as plesiomorphies of the family. Specifically, the dorsal-oriented fimbriate gills, projected frons and slim labial palpi in nymphs plus large reddishly pigmented wings, many crossveins, 4-segmented forceps with a relatively long basal segment, fused penes and unforked anal vein show that this species is closer to the taxon Fossoriae rather than to the previously considered Potamanthidae. To reflect its primitive position, a new genus, Pulchephemera Zhou gen. n., is established for this species, Pulchephemera projecta comb. n. Its eggs and observed biology are also described. Full article