Accepted by M. Vences: 1 Oct. 2010; published: 28 Oct. 2010 33 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2010 · Magnolia Press Zootaxa 2660: 33–45 (2010) www.mapress.com/ zootaxa/ Article A new species of Leptolalax (Anura: Megophryidae) from Vietnam and further information on Leptolalax tuberosus JODI J. L. ROWLEY 1,5 , HOANG DUC HUY 2 , LE THI THUY DUONG 2 , DAU QUANG VINH 3 & CAO TIEN TRUNG 4 1 Australian Museum, 6 College St, Sydney, NSW, 2010, Australia 2 Faculty of Biology, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh City, Vietnam 3 Institute of Ecology and Biological Resources, 18 Hoang Quoc Viet, Nghia Do, Tu Liem, Hanoi, Vietnam 4 Biology Faculty, Vinh University, 182 Le Duan St, Vinh City, Vietnam 5 Corresponding author: E-mail: Jodi.Rowley@austmus.gov.au Abstract We describe a new species of megophryid frog from central Vietnam. Leptolalax croceus sp. nov. is most similar to L. tuberosus, but distinguished from this and all other Leptolalax species by its bright orange belly in life and by its unique, complex advertisement call consisting of 4–6 variably pulsed notes with a dominant frequency of 2635–3000 Hz. In contrast, L. tuberosus has an advertisement call consisting of a single, weakly pulsed note lasting 54–78 ms with a dominant frequency of 2584–2756.2 Hz. Leptolalax croceus sp. nov. can be further distinguished from its congeners by a combination of an indistinct tympanum, highly tuberculate dorsum, medium body size (22.2–27.3 mm in 16 adult males), head slightly wider than long, rudimentary webbing between toes I–III, no webbing between toes III–V, no lateral fringing on toes, and no ventrolateral glands. The new species is only known from a single locality in evergreen forest at 1316 m elevation. Males were found calling from leaf litter and low vegetation adjacent to a shallow, rocky stream. We suggest the species should be considered Data Deficient following IUCN’s Red List categories. Key words: Acoustics, Anura, Leptolalax croceus sp. nov., Leptolalax tuberosus, Vietnam, Southeast Asia Introduction The genus Leptolalax (Dubois 1983) currently consists of 27 species found in rocky streams in hilly evergreen forest throughout Southeast Asia, southern China and northeastern India (Frost 2010, Rowley et al. 2010). Leptolalax are small frogs of the forest floor, cryptic in both colouration and behaviour, with advertisement calls easily mistaken for that of an orthopteran. As a result, they are easily overlooked during field surveys. Leptolalax are also morphologically cryptic, with species being difficult to distinguish based upon external morphology, especially in preservative. Unsurprisingly, the genus Leptolalax contains a high proportion of undiagnosed diversity, with new species continuously being described from throughout their range (eg. Matsui et al. 2009; Rowley & Cao 2009; Das et al. 2010; Rowley et al. 2010 Sengupta et al. 2010). Species discovery in the genus has been accelerated by increased survey efforts and the incorporation of molecular and acoustic information in delineating species boundaries. During recent field work in central Vietnam, we discovered a species of Leptolalax superficially resembling L. tuberosus, a species recorded from only 11 km away. The new species is distinct in having a bright orange belly, and a relatively complex advertisement call, both of which are unique within the genus. Here we describe this species as new, and provide further information on L. tuberosus, including the first description of its advertisement call.