biostudies-literatureUnknown1135Kaltenbach TA reinvestigation of type and other material of <i>Baetisjavanicus</i> Ulmer, 1913 and <i>Baetissabahensis</i> Müller-Liebenau, 1984, together with new material from Southeast Asia revealed a new genus, <i>Branchiobaetis</i> <b>gen. nov.</b> The above species are formally assigned to the new genus <i>Branchiobaetis</i> <b>gen. nov.</b> It is characterized by the presence of accessory gills ventrally near fore coxa and at the base of maxillae, a peculiar folding of the gonostyli developing under the cuticle of last instar male larvae, together with a unique combination of other larval characters. Besides the two formerly described species, five new species are identified using a combination of morphology and molecular characters (COI, Kimura 2-parameter distances), four species from Sumatra and one from the Philippines. They are described and illustrated at the larval stage. Additionally, a complementary description of larva and adult stages of the generic type species <i>B.javanicus</i> <b>comb. nov.</b> as well as the first description of the eggs are provided. Furthermore, new reports of <i>B.javanicus</i> <b>comb. nov.</b> and <i>B.sabahensis</i> <b>comb. nov.</b> are indicated. The distribution of <i>Branchiobaetis</i> <b>gen. nov.</b> includes the Indonesian Sunda Islands, Borneo, and the Philippines. A key to the larval stage of all species is provided.ZooKeys1-59https://www.ebi.ac.uk/biostudies/studies/S-EPMC9836713biostudies-literatureA widespread new genus of Baetidae (Baetidae, Ephemeroptera) from Southeast Asia.PMC9836713Kluge NJGattolliat JLKaltenbach TfalseA widespread new genus of Baetidae (Baetidae, Ephemeroptera) from Southeast Asia.A reinvestigation of type and other material of <i>Baetisjavanicus</i> Ulmer, 1913 and <i>Baetissabahensis</i> Müller-Liebenau, 1984, together with new material from Southeast Asia revealed a new genus, <i>Branchiobaetis</i> <b>gen. nov.</b> The above species are formally assigned to the new genus <i>Branchiobaetis</i> <b>gen. nov.</b> It is characterized by the presence of accessory gills ventrally near fore coxa and at the base of maxillae, a peculiar folding of the gonostyli developing under the cuticle of last instar male larvae, together with a unique combination of other larval characters. Besides the two formerly described species, five new species are identified using a combination of morphology and molecular characters (COI, Kimura 2-parameter distances), four species from Sumatra and one from the Philippines. They are described and illustrated at the larval stage. Additionally, a complementary description of larva and adult stages of the generic type species <i>B.javanicus</i> <b>comb. nov.</b> as well as the first description of the eggs are provided. Furthermore, new reports of <i>B.javanicus</i> <b>comb. nov.</b> and <i>B.sabahensis</i> <b>comb. nov.</b> are indicated. The distribution of <i>Branchiobaetis</i> <b>gen. nov.</b> includes the Indonesian Sunda Islands, Borneo, and the Philippines. A key to the larval stage of all species is provided.2022-01-01T00:00:00Z20222025-04-18T21:17:26.343Z2025-04-07T09:15:46.984ZS-EPMC98367133676180010.3897/zookeys.1135.93800