Abstract
This paper focuses on five species of Polyplacophora (Mollusca) collected from Lavanono, southern Madagascar. Ischnochiton sirenkoi is described as a new species and is compared with the two Ischnochiton species known from Madagascar, I. yerburyi (E.A. Smith, 1891) and I. sansibarensis Thiele, 1909, and with all known Indian Ocean Ischnochiton species. Findings for the other species here discussed provide a significant extension of previously known geographical range. Chaetopleura chelazziana Ferreira, 1983 is reported for the first time in the chiton fauna of Madagascar. The taxonomic status of Callistochiton ashbyi (Barnard, 1963), previously considered a synonym of C. crosslandi Sykes, 1907, is discussed. This taxon, which was described from a unique intermediate valve from South Africa, is re-evaluated and recognized as a valid species, differing from C. crosslandi in several significant characters. We also present an unusual feature detected in almost all the specimens of Cryptoplax dupuisi Ashby, 1931, which are characterized by the absence of dorsal girdle spicules on the first four valves, a feature never reported in other chiton species. Type material of Callistochiton madagassicus Thiele, 1909, Chiton ashbyi (Barnard, 1963) is figured.
Highlights
Within the Indo-Pacific biodiversity and biogeography, the marine fauna of Madagascar is significant because of the presence, off Tuléar, of one of the world’s longest reefs (Spalding et al 2001)
During ongoing research on the marine mollusca that inhabit the southern Madagascar coasts, one of us (GP) has come across many specimens of chitons, some of which belong to a new species of Ischnochiton, and others of species either rarely reported or unrecorded from this area
The chitons from Lavanono allow us to increase our knowledge of Madagascar chitons
Summary
Within the Indo-Pacific biodiversity and biogeography, the marine fauna of Madagascar is significant because of the presence, off Tuléar, of one of the world’s longest reefs (Spalding et al 2001). The chiton fauna of Madagascar has been the subject of a number of studies, resulting in a better appreciation of the taxonomy of some elusive species and in a reconsideration of their geographic dis tribution (Leloup 1981; Kaas 1986; Dell’Angelo et al 2004b, 2010b). During ongoing research on the marine mollusca that inhabit the southern Madagascar coasts, one of us (GP) has come across many specimens of chitons, some of which belong to a new species of Ischnochiton, and others of species either rarely reported or unrecorded from this area
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