Accepted by L. Jacobus: 15 Apr. 2014; published: 26 May 2014 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2014 Magnolia Press Zootaxa 3802 (2): 193–208 www.mapress.com/zootaxa/ Article 193 http://dx.doi.org/10.11646/zootaxa.3802.2.3 http://zoobank.org/urn:lsid:zoobank.org:pub:8585D3AD-653C-4ED6-8523-FB6427A313C5 What is Ecdyonurus sumatranus Ulmer, 1939? A contribution to the knowledge of the genus Rhithrogena in the Oriental Region (Ephemeroptera, Heptageniidae) MICHEL SARTORI 1,2 1 Zoologisches Museum und Biozentrum Grindel, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany. E-mail: michel.sartori@uni-hamburg.de 2 Museum of Zoology, Palais de Rumine, Place Riponne 6, CH-1005 Lausanne, Switzerland. E-mail : michel.sartori@vd.ch Abstract The species Ecdyonurus sumatranus Ulmer, 1939 was described from Sumatra based on a female imago and a single nymph. It was designated as the type-species of the genus Ecdyonuroides Dang, 1967, erected because of the peculiar mor- phology of the nymph. This genus was put into synonymy later and the species is currently known as Thalerosphyrus su- matranus (Ulmer, 1939). The female imago holotype of Ecdyonurus sumatranus Ulmer, 1939 is reinvestigated and revealed to belong to the genus Rhithrogena Eaton, 1881. The combination Rhithrogena sumatrana (Ulmer, 1939) comb. nov. is thus proposed. The nymphs described by Ulmer (1939) from Java sub. nom. Rhithrogena parva (?) are associated to this species, and are redescribed with new material coming from Java and Lombok. Rhithrogena parva (Ulmer, 1912) is redescribed based on the syntype series from Taiwan and male genitalia are illustrated for the first time. Supplementary description is provided for the nymph of Rh. parva and for the one of Rh. ampla Kang & Yang, 1994, also from Taiwan. The status of the subgenus Tumungula Zhou & Peters, 2004 is briefly discussed. The nymph associated by Ulmer (1939) to Ecdyonurus sumatranus is renamed Thalerosphyrus lamuriensis sp. nov. The genus Ecdyonuroides Dang, 1967 is con- sidered as a synonym of Rhithrogena syn. nov. Key words: Java, Sumatra, Lombok, Taiwan, Rhithrogena, Thalerosphyrus, Ecdyonuroides, Tumungula, new combina- tion, new synonym, new species Introduction In his work devoted to the Ephemeroptera of the Sunda Islands, Ulmer (1939) described the species Ecdyonurus sumatranus (Heptageniidae), based only on two specimens; a female imago (type specimen) from south Sumatra and a half grown nymph from western Sumatra. Based on Ulmer’s writing, he would not have described this species on this scarce material if he was not convinced that both specimens belonged to the genus Ecdyonurus. Despite this statement, he recognized that the nymph did not possess all characteristics of the genus Ecdyonurus, especially by the absence of posterolateral expansions of the prothorax, but he suggested it could be due to the fact that the nymph was only half grown. This specimen possesses peculiar structures, such as the unique highly- developed posterolateral expansions of the sternites V–VIII. The scattered setae on the galea-lacinia (Ulmer 1939, fig. 436) are characteristic of the subfamily Ecdyonurinae. Dang (1967) proposed a new genus from Vietnam, called Ecdyonuroides, to accommodate a peculiar nymph of the family Heptageniidae, with long posterolateral abdominal expansions, he called Ecdyonuroides vietnamensis. He recognized the similarities between his nymph and the one described by Ulmer (1939), transferred the latter to his new genus as Ecdyonuroides sumatrensis, (misspelling!) and designated E. sumatranus as the type species of the genus Ecdyonuroides. Later, Braasch & Soldán (1984) suggested to put Ecdyonuroides in synonymy with Thalerosphyrus Eaton, 1881, because the rearing of a nymph of Ecdyonuroides vietnamensis gave an adult similar to the genus Thalerosphyrus. They proposed the new combinations Thalerosphyrus vietnamensis (Dang, erroneously spelled Thanh) and they put in synonymy Th. sumatranus (Ulmer) with Th. sinuosus (Navás, 1933) without more explanations.