Chiton;Gymnoplax;Mucrosquama;Radsia;Rhyssoplax;Sypharochiton;Tegulaplax Rafinesque 1815

Subfamily Chitoninae Rafinesque, 1815 Genus Rhyssoplax Thiele, 1893 Type species. Chiton affinis Issel, 1869, by subsequent designation (International Committee of Zoological Nomenclature 1971, Opinion 951, as proposed by Beu et al. 1969). Distribution. Rhyssoplax is reported from the Oligocene up to the Recent, with a present distribution in the Indo-West Pacific, and eastern Atlantic Ocean, Mediterranean included. The fossil record encompasses the Oligocene of New Zealand (Lee et al. 2014; Wu & Lee 2024), Neogene of Europe (Dell’Angelo et al. 2004, 2015a; Garilli et al. 2005; Studencka & Dulai 2010), Africa (Algeria: De Lamothe 1911; Tunisia: Castany et al. 1956), New Zealand (Beu & Maxwell 1990; Sutherland et al. 1995) and Japan (Itoigawa et al. 1976), Pleistocene of the Red Sea (Dell’Angelo et al. 2020a) and Madeira (Gerber et al. 1989), Holocene of Japan (Kuroda et al. 1980). Remarks. The genus Chiton was subdivided into numerous subgenera by Kaas et al. (2006), some of which (e.g., Rhyssoplax Thiele, 1893) later erected to genus by Sirenko (2006), based mainly upon soft part morphology. We consider here ten species attributed to Rhyssoplax, whose characteristics are summarized in tables 14 and 15, conveniently arranged in two groups based upon differences in tegmentum sculpture of HV, LA and PA. The first group includes four species, with the presence of more or less pronounced radial ribs [R. miocenica (Michelotti, 1847), R. olivacea (Spengler, 1797), R. saeniensis (Laghi, 1984) and R. sulcomarginata ((Dell’Angelo, Giuntelli, Sosso & Zunino, 2016)] (Tab. 14). The second group includes 6 species [R. assurrecta Dell’Angelo, Landau, Van Dingenen & Ceulemans, 2018, R. capecchii (Chirli, 2004), R. corallina (Risso, 1826), R. etrusca (Dell’Angelo & Forli, 1995), R. garillii sp. nov. and R. phaseolina (Monterosato, 1879)], whose areas are instead smooth (Tab. 15).