Zootaxa 4747 (2): 275–301 ISSN 1175-5326 (print edition) https://www.mapress.com/j/zt/ Article ZOOTAXA Copyright © 2020 Magnolia Press ISSN 1175-5334 (online edition) https://doi.org/10.11646/zootaxa.4747.2.3 http://zoobank.org/urn:lsid:zoobank.org:pub:6D32355F-DBFD-44C6-AC13-086F13A35066 Dragons in neglect: Taxonomic revision of the Sulawesi sailfin lizards of the genus Hydrosaurus Kaup, 1828 (Squamata, Agamidae) WOLFGANG DENZER1,6, PATRICK D. CAMPBELL2, ULRICH MANTHEY3, ANDREA GLÄSSER-TROBISCH4 & ANDRÉ KOCH5 1Society for Southeast Asian Herpetology, Rubensstrasse 90, 12157 Berlin, Germany 2Department of Life Sciences, Darwin Centre, Natural History Museum, Cromwell Road, South Kensington, London SW7 5BD, Eng- land 3Society for Southeast Asian Herpetology, Kindelbergweg 15, 12249 Berlin, Germany 4Hauptstrasse 7, 56414 Bilkheim, Germany 5Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany 6Corresponding author. E-mail:
[email protected] Abstract Currently three different species are recognized within the Southeast Asian agamid genus Hydrosaurus: H. amboinensis (Schlosser, 1768) from Ambon, Seram, Sulawesi and New Guinea, H. pustulatus (Eschscholtz, 1829) from the Philippines and H. weberi Barbour, 1911 from Halmahera and adjacent islands. Historically, two additional species were described from the island of Sulawesi, but were synonymized with H. amboinensis more than a century ago and have been treated as such in most subsequent publications. In order to revise the taxonomy and diversity of these enigmatic agamid lizards, we examined the corresponding type specimens and additional material originating from Sulawesi and compared them to photographs of live specimens from field trips. Due to differences in colour pattern and scalation characters, we resurrect the taxa celebensis Peters, 1872 and microlophus Bleeker, 1860 from the synonymy of H.