Accepted by S. Carranza: 12 March 2008; published: 28 Apr. 2008 61 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2008 · Magnolia Press Zootaxa 1758: 61–68 (2008) www.mapress.com/ zootaxa/ Naming one of the world’s rarest chelonians, the southern Batagur PETER PRASCHAG 1 , ROBERT S. SOMMER 2 , COLIN MCCARTHY 3 , RICHARD GEMEL 4 & UWE FRITZ 2,5 1 Am Katzelbach 98, A-8054 Graz, Austria. E-mail: peter@praschag.at 2 Museum of Zoology (Museum für Tierkunde), Natural History State Collections Dresden, Königsbrücker Landstr. 159, D-01109 Dres- den, Germany. E-mails: robert.sommer@snsd.smwk.sachsen.de, uwe.fritz@snsd.smwk.sachsen.de 3 Reptile and Amphibian Group, Department of Zoology, The Natural History Museum, Cromwell Road, London SW5 7BD, UK. E-mail: c.mccarthy@nhm.ac.uk 4 Naturhistorisches Museum Wien, Burgring 7, A-1010 Wien, Austria. E-mail: richard.gemel@nhm-wien.ac.at 5 Corresponding author. E-mail: uwe.fritz@snsd.smwk.sachsen.de Abstract Using mtDNA sequences of historical museum specimens, including the herein designated lectotype of Tetraonyx affinis Cantor 1847 and topotypic specimens of Trionyx (Tetraonyx) cuvieri Gray 1831 and Tetronyx longicollis Lesson 1834, we demonstrate that the name Batagur affinis (Cantor 1847) has to be used for a recently identified critically endangered terrapin species from Southeast Asia. Further, we provide evidence that Batagur baska (Gray 1830) historically was dis- tributed from north-easternmost India and Bangladesh to at least the Ayeyarwady and Bago estuaries in Myanmar while B. affinis occurs in the southern Malay Peninsula and Sumatra. The taxonomic allocation of the extant and extirpated Batagur populations in the northern Malay Peninsula, Cambodia and southern Vietnam remains unclear. A museum specimen from the mid-19 th century suggests that B. baska once also occurred in the Indus Delta of southern Pakistan. Key words: Southeast Asia, South Asia, lectotype designation, taxonomy, endangered species Introduction Batagur baska (Gray 1830), a large estuarine terrapin reaching a shell length of approximately 60 cm, is one of the most critically endangered chelonians of the world (IUCN, 2007; Kalyar et al., 2007). Historically, it occupied a range extending from the Brahminy-Baitarini Delta (Orissa) and the Sundarbans Region (north- easternmost India, Bangladesh) through the Ayeyarwady (Irrawaddy) River mouth in Myanmar and the Malay Peninsula (southern Thailand, Malaysia) to Sumatra, Cambodia and southern Vietnam; however, it was extir- pated in much of its former range (Moll, 1980; Das, 1991, 1995, 2001; Ernst et al., 2000; Platt et al., 2003; Kalyar et al., 2007). Batagur baska is more or less confined to estuaries, mangrove belts and inshore beds of marine vegetation. During the reproductive season adult terrapins may travel far upstream to reach nesting beaches that are often located well above tidal influence (Kalyar et al., 2007). In a recent paper, Praschag et al. (2007) demonstrated that B. baska actually consists of two genetically well-differentiated species. While it is clear that the name B. baska (Gray 1830), with type locality of “India”, has to be restricted to the species occurring in north-eastern India and Bangladesh, there are several candidates available for naming the second species from Indonesia and Malaysia (Praschag et al., 2007). As national and international conservation mea- sures are significantly influenced by zoological nomenclature, it is crucial to determine its valid name. To accomplish this goal, here we use mtDNA sequence data of historical museum specimens, including a syntype