Isonychia taishunensis Huang, Shen, Zhang & Cheng sp. nov. is described based on larval samples from Taishun County, Zhejiang Province, China. The new species is distinguished from other species of Isonychia Eaton by the following characters: gill plates with spines apically, the color of abdominal tergum X, color pattern of abdominal terga I–IX, and color pattern of each gill plate. The genetic distance between the new species and other species of Isonychia is over 10% using the Kimura 2-parameter model. The phylogenetic relationship of I. taishunensis is close to the clade of I. japonica Ulmer and I. ussurica Bajkova. The morphological characters and molecular data (COX1, Kimura 2-parameter) support that this new species represents the ninth species of the genus Isonychia in China. The modified key to known larvae of the genus Isonychia is provided.

Heptageniidae are known for their flat heads and bodies and are divided into three subfamilies. Despite the extensive diversity within this group and considerable efforts made to understand their evolutionary history, the internal classifications and origin time of Heptageniidae remains controversial. In this study, we newly sequenced 17 complete mitogenomes of Heptageniidae to reconstruct their phylogenetic positions within this family. Because of the ambiguous time of origin, our study also estimated the divergence time within Heptageniidae based on five fossil calibration points. The results of BI and ML trees all highly supported the monophyly of Heptageniidae and three subfamilies. The phylogenetic relationship of Rhithrogeninae + (Ecdyonurinae + Heptageniinae) was also recovered. The divergence time showed that Heptageniidae originated from 164.38 Mya (95% HPD, 150.23–181.53 Mya) in the mid-Jurassic, and Rhithrogeninae originated from 95.54 Mya (95% HPD, 73.86–120.19 Mya) in the mid-Cretaceous. Ecdyonurinae and Heptageniinae began to diverge at 90.08 Mya (95% HPD, 68.81–113.16 Mya) in the middle Cretaceous. After morphological identification, analysis of the mitogenome’s composition, genetic distance calculation, phylogenetic analysis, and divergence time calculation, we suggest that two different populations of Epeorus montanus collected from Aksu, Xinjiang Uygur Autonomous Region (40°16′ N, 80°26′ E) and Xinyuan, Xinjiang Uygur Autonomous Region (43°20′ N, 83°43′ E) in China are cryptic species of E. montanus, but further detailed information on their morphological characteristics is needed to fully identify them.

As one of the four primary evolutionary groups within myriapods, centipedes (Chilopoda) comprise approximately 3150 valid species. Recent molecular studies have begun to elucidate the phylogeny and time to divergence in Chilopoda; yet, identifying scutigeromorphs at the species level remains a notoriously challenging task. In this study, we obtained seven new complete mitogenomes of Thereuopoda clunifera (Wood, 1862) to investigate the phylogeny and divergence times of Chilopoda. Both maximum likelihood (ML) and Bayesian inference (BI) analyses recovered the relationship of (Scutigeromorpha + (Scolopendromorpha + (Lithobiomorpha + Geophilomorpha))). For Scutigeromorpha, seven newly sequenced mitogenomes of T. clunifera were divided into four distinct clades. Divergence time estimates suggest that the basal split of Chilopoda occurred during the Middle Ordovician period, with the origins of Scolopendromorpha, Lithobiomorpha, and Geophilomorpha dating to the Devonian period. Factors such as warm climates, coevolution between predator and prey, and the rifting of the Hainan Island may have driven the diversification of Scutigeromorpha. Based on genetic distance, the delimitation of molecular species, phylogenetic relationships, and divergence time analyses, we identified three cryptic species that existed within T. clunifera. This exceptionally high degree of hidden diversity can be ascribed to the morphological stasis that has occurred since the Paleozoic era and taxonomic impediment.

One new species of bristletail of the genus Silvestrichilis (Microcoryphia: Machilidae), S. shiyanensis Shen, Wang & Zhang, sp. nov. is illustrated and described based on mature adult samples from Wudang Mountain, Shiyan City, Hubei Province, China. The species is named after Shiyan City, the original collection of the type specimens. The following characteristics can be used to distinguish the new species from Silvestrichilis confucius and other congeners: length of the contact line of compound eyes; distribution of setae on articles of the maxillary palpus, labial palpus and legs; length to width ratio for the ultimate article of labial palpus; number of divisions of parameres of male. A key to all Silvestrichilis species in China and the phylogenetic relationship of S. shiyanensis sp. nov. based on COX1 are also presented.

Scutigeromorph centipedes are morphologically distinctive myriapods that have historically received limited scientific attention, particularly in China. The taxonomy of the genus Thereuopoda Verhoeff, 1904 has remained largely unresolved since the late 1970s, and recent molecular evidence has indicated the presence of cryptic species within this group. In this study, we describe two new species, T. kaijiangensis sp. nov. Ji, Shen & Zhang from Kaijiang County, Dazhou City, Sichuan Province, China, and T. edgecombei sp. nov. Ji, Liu & Zhang from Chengmai County, Hainan Province, China. Comprehensive morphological descriptions and detailed illustrations are provided for both species, along with an updated diagnostic key to all currently recognized Thereuopoda species in China. Phylogenetic analyses conducted using both maximum-likelihood and Bayesian-inference methods consistently support the monophyly of the genus Thereuopoda and further validate the taxonomic distinctness of the two newly described species.

Siphlonuroidea is a superfamily within Ephemeroptera, yet the phylogenetic relationships among its constituent families and their placement relative to other mayfly lineages remain unresolved. To address these questions, we generated and analyzed 16 newly assembled mitochondrial genomes from 14 species across Ephemeroptera, including three species of Ameletidae, four of Siphlonuridae, and nine mitochondrial genomes from seven species of Isonychiidae. Comparative mitogenomic analysis revealed two distinct tRNA gene rearrangement patterns within Siphlonuridae, including trnI-trnQ-trnM-trnQ-trnM-trnQ-trnM-trnQ-trnM and trnI-trnM-trnQ-trnM. In contrast, all Ameletidae mitogenomes share an identical rearrangement of trnI-trnQ-trnM-trnM, which constitutes a potential synapomorphy supporting the monophyly of this family. Compositional analysis further showed that Siphlonuridae and Ameletidae exhibit significantly higher and highly similar A+T contents, clustering together in hierarchical analyses. This characteristic contrasts sharply with Isonychiidae, which displays markedly lower A+T content. Phylogenomic inference based on the PCG12 dataset supports a sister-group relationship between Siphlonuridae and Ameletidae, with this clade itself forming the sister group to a well-supported clade of Isonychiidae and Heptageniidae. Divergence time estimation places the origin of the Ameletidae and Siphlonuridae lineage in the Late Jurassic (174.71 Mya), while Isonychiidae diverged in the Early Cretaceous (136.81 Mya). In conclusion, Siphlonuridae and Ameletidae show a closer affinity and belong to Siphlonuroidea. Isonychiidae shares a closer relationship with Heptageniidae and remains outside Siphlonuroidea. Siphluriscidae is recovered as the sister lineage to all other extant Ephemeroptera, confirming its status as the earliest-diverging extant mayfly lineage.