Nuttallochiton martiali

Schwabe, Enrico, Försterra, Günter, Häussermann, Verena, Melzer, Roland R. & Schrödl, Michael, 2006, Chitons (Mollusca: Polyplacophora) from the southern Chilean Comau Fjord, with reinstatement of Tonicia calbucensis Plate, 1897, Zootaxa 1341, pp. 1-27 : 20-21

Nuttallochiton martiali (de Rochebrune in de Rochebrune & Mabille, 1889)

( Figure 14 )

Tonicia martiali de Rochebrune in de Rochebrune & Mabille, 1889: H.139–H.140, pl. 9, figs. 8a–b. Detailed bibliography and synonymy in Kaas & Van Belle (1987: 199).

While evaluating the underwater pictures of Comau Fjord chitons we came across a single specimen ( Figure 14 ) that, at first sight, strongly resembles Plaxiphora aurata . However, the figured specimen differs in the following characters: 1) P. a u r a t a has long hairs at the dorsal perinotum side, while in N. martiali they are missing, 2) N. martiali has 8 prominent radial ribs on the head valve, whereas in P. aurata the head valve is only weakly sculptured, 3) radial ribs on lateral areas of N. martiali are wider and more strongly raised; in contrast they are moderately raised, widely separated and narrow in P. a u r a t a, 4) while the pleural areas are smooth in P. aurata , longitudinally to obliquely arranged folds occur in N. martiali , 5) the dorsum is obviously stronger carinated in N. martiali , and 6) apices are less prominent in N. martiali , while in P. aurata the posterior valve margin is convex on both sides of the protruding apex.

Unfortunately there is no reference material of this single specimen from station 7 (15 m depth) available, and we failed to find more specimens. However, a careful comparison of the illustrated specimen with an approximately 42 mm long specimen, from the Canal Betecoi (43°56’S 73°49’W), collected in a depth between 8–13 m (ZSM Moll 20050419), leaves no doubt of its correct identification.

Although Kaas & Van Belle (1987) considered Nuttallochiton martiali to be “rather common”, it is obviously rare along the southern Chilean coast. Neither the Lund Expedition ( Leloup 1956) nor the extensive sampling efforts in the Chonos Archipelago ( Reid & Osorio 2000, Osorio et al. 2002, Osorio & Reid 2004) found Nuttallochiton martiali in this area. According to Sirenko’s (2006b) observation, Nuttallochiton martiali is a “rather rare species”, bathymetrically ranging from 0– 92 m. The photograph of a living specimen from Comau Fjord is the northernmost record of N. martiali .

Total specimen number per 21 2 8 109 species

Figures

FIGURE 14. Nuttallochiton martiali (de Rochebrune in de Rochebrune & Mabille, 1889) in situ (NRS), at station 7. 15. Underwater photograph of Chiton magnificus Deshayes, 1827 in situ (NRS), at station 7. 16. Underwater photograph of Tonicia calbucensis Plate, 1897 in situ (NRS), at station 7. 17. Underwater photograph of Tonicia chilensis (Frembly, 1827) in situ (NRS), at station 7. 18. Underwater photograph of Tonicia atrata (Sowerby, 1840) in situ (NRS), at station 11. 19. Underwater photograph of Plaxiphora aurata (Spalowsky, 1795) in situ (ZSM Moll 20040961), at station 7, illustrated specimen measures c. 24 mm in length.