Testudinidae — Aldabrachelys arnoldi 028.1 Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group A.G.J. Rhodin, P.C.H. Pritchard, P.P. van Dijk, R.A. Saumure, K.A. Buhlmann, J.B. Iverson, and R.A. Mittermeier, Eds. Chelonian Research Monographs (ISSN 1088-7105) No. 5, doi:10.3854/crm.5.028.arnoldi.v1.2009 © 2009 by Chelonian Research Foundation • Published 18 October 2009 Aldabrachelys arnoldi (Bour 1982) – Arnold’s Giant Tortoise JusTin GerlAch 1 1 133 Cherry Hinton Road, Cambridge CB1 7BX, United Kingdom [jstgerlach@aol.com] summAry. – Arnold’s giant tortoise, Aldabrachelys arnoldi (= Dipsochelys arnoldi) (Family Testudinidae), from the granitic seychelles, is a controversial species possibly distinct from the Aldabra giant tortoise, A. gigantea (= D. dussumieri of some authors). The species is a morphologi- cally distinctive morphotype, but has so far not been genetically distinguishable from the Aldabra tortoise, and is considered synonymous with that species by many researchers. captive reared juveniles suggest that there may be a genetic basis for the morphotype and more detailed genetic work is needed to elucidate these relationships. The species is the only living saddle-backed tortoise in the seychelles islands. it was apparently extirpated from the wild in the 1800s and believed to be extinct until recently purportedly rediscovered in captivity. The current population of this morphotype is 23 adults, including 18 captive adult males on mahé island, 5 adults recently in- troduced to silhouette island, and one free-ranging female on cousine island. successful captive breeding has produced 138 juveniles to date. DisTriBuTion. – seychelles. restricted to the granitic islands, but original distribution unknown. currently occurs as a small introduced population on silhouette, a single female on cousine, and several males in non-breeding captive groups on mahé. synonymy. – Dipsochelys arnoldi Bour 1982, Aldabrachelys arnoldi. suBspecies. – none. sTATus. – iucn 2008 red list: not evaluated (proposed listing: extinct in the Wild, eW); ciTes: Appendix ii (as Testudinidae spp.). Taxonomy. — A stuffed specimen of this species pre- sented by the 13th Earl of Derby was recognized as distinct from Testudo elephantina Duméril and Bibron 1835 (a subjective synonym of Testudo dussumieri Gray 1831 and Testudo gigantea Schweigger 1812, the Aldabra tortoise), by Günther (1877), but included under Testudo daudinii Duméril and Bibron 1835. Boulenger (1889) followed Günther. Later, in his review of the giant tortoises, Arnold Figure 1. Adult male Aldabrachelys arnoldi, Seychelles. Photo by John Pemberton.