Lepidochitona Gray, 1821

Genus Lepidochitona Gray, 1821 View in CoL

Type species. Chiton marginatus Pennant, 1777 (= Chiton cinereus Linnaeus, 1767 ), by monotypy.

Genus distribution. Mediterranean Sea, northeastern Atlantic Ocean, Caribbean Sea and adjacent western Atlantic Ocean, Pacific coast near Central America, south Atlantic and Indian oceans.

Lepidochitona View in CoL cubensis sp. nov. ( Figs 1–5 View FIG View FIG View FIG )

Zoobank registration: urn:lsid:zoobank.org:act:F164A8EF-1A4B-41A2-9145-C9C2496E2A39

Type material. Holotype ( ZIN 2588 View Materials ), now disarticulated consisting of SEM stub of valves I, II, V, VIII, part of perinotum and radula, and vial with other valves,

Type locality. Caribbean Sea , Cuba, Pinos Island, Punta Colombo, intertidal, sand, in sea grass Thalassia testudinum .

Etymology. Named after Cuba.

Distribution. Only known from the type locality.

Diagnosis. Chiton of very small size, elongate oval. Valves moderate elevated, carinated, beaked, lateral area not raised, mucro anterior, postmucronal slope slightly concave. Tegmentum smooth, with rather rare small square grooves located mainly in the anterior part of the valves, except for the tail valve, where there are no grooves at all. Slit formula: 10/1–2/13. Girdle covered with small cylindrical and bluntly pointed spicules, among them, rare scattered tufts with 1, 2 rare 3 bent short needles. Central and first lateral teeth of radula with rounded blade, head of major lateral teeth of radula with three blunt denticles. Holotype with 8 gills from each side.

Description.The single specimen has a deformity (depression) which is visible on all valves. This depression probably occurred during the growth of the mollusk and is the result of an external influence, so it is not considered in the description of the species. Holotype (BL 5.0 mm) with elongate oval body. Shell moderately elevated (dorsal elevation 0.33), back carinated, valves beaked. Color of tegmentum light brown, mottled with brown spots.

Head valve semicircular, posterior margin widely V-shaped. Intermediate valves short, width 2.5 times exceeds length, front margin slightly concave in the jugal part, straight and somewhat obliquely posteriorly directed in the lateral parts, side margins rounded, hind margin concave at both sides of the distinctly beaked apex, lateral areas not raised. Tail valve semicircular, slightly narrower than the head valve, front margin concave in the jugal part and straight in pleural part, mucro anterior, postmucronal slope slightly concave.

Tegmentum smooth, with concentric growth lines and with rather rare, small, square grooves located mainly in the anterior part of the valves, except for the tail valve, where there are no grooves at all. Microaesthetes are arranged in longitudinal lines on central areas of intermediate valves, on antemucronal area of tail valve, and in radial lines on head valve, on lateral areas of intermediate valves and postmucronal area of tail valve.

Articulamentum moderately developed, white, very porous. Apophyses broadly and irregularly triangular with rounded top, the width of jugal sinus less the width of apophyses. Slit formula 10/1–2/13, slits rather wide, slit rays present in all valves, fine, eaves spongy, porous.

Girdle rather narrow, width 250 µm near valve V, brownish, dorsally covered with small cylindrical and bluntly pointed spicules (25–30 x 10 μm), among them, rare scattered tufts with 1, 2 rare 3 bent needles (75–200 x 8–12 μm). Marginal elements of two kinds: fringe of elongate, straight, longitudinally ribbed in dorsal side, sharply pointed needles (130 x 12–13 μm) and one row of long, smooth, rectangular scales (70 x 20 μm). Ventral part of girdle covered with smooth, lanceolate scales (34–45 x 11 μm).

Radula 1.5 mm long with 22 rows of mature teeth. Central tooth length is 2.5 times its width, first lateral teeth elongate, wing-shaped with rounded blade, major lateral teeth with tridentate cusp, denticles rather blunt, central denticle slightly larger, distal part of large uncinal teeth with wide fringe.

Eight gills on each side, arranged from valves IV–VII.

Remarks. As already mentioned the genus includes species with smooth and granular tegmentum. Lepidochitona cubensis sp. nov. and L. bullocki can be referred to the intermediate group of chitons of this genus in which granules on tegmentum are formed as a result of appearance of square zones on margins as was noted by Garsí-Ríos [2011]. In the new species areas of granular tegmentum only begin to form on anterior margins of valves, while in L. bullocki most of the tegmentum and especially the lateral area are already covered with granules. The new species differs from L. bullocki , not only by more developed granular surface of tegmentum, but also by a number of other morphological characters: 1) dorsal needles are scattered singly or in tufts of 2–3 needles (vs. up to 10 needles in each tuft are located in the sutures in L. bullocki ; 2) slit formula of new species 10/1–2/13 (vs. 9/1/ 16 in L. bullocki ); 3) 8 gills (vs. 11-13 in L. bullocki ); 4) intermediate valves are carinated (vs. rounded in L. bullocki ); 5) square grooves are absent in the tail valve (vs. present in L. bullocki ); 6) denticles of the cusp of major lateral teeth are rather blunt (vs. the denticles sharp in L. bullocki ). It should be noted that the sizes of the compared specimens of both species were similar, which excludes the influence of age variability. The new species is distinguished from all other species of the genus Lepidochitona except L. bullocki by the presence of square grooves in the tegmentum of valves.

There are 6 species of the genus Lepidochitona in the Caribbean region, including the Florida coast, of which 3 species ( L. rosea , L. liozonis , and L. pseudoliozonis have smooth tegmentum, 1 species ( L. rufoi ) has granular tegmentum, and the two species L. bullocki and L. cubensis sp. nov. occupy an intermediate position. The new species appears to be closer to species with smooth tegmentum in tegmentum

Lepidochitona cubensis sp. nov. from Cuba 51

sculpture than L. bullocki , as most of the tegmentum is smooth, excluding a small part of the surface where square grooves occur and no grains at all.