Callistochiton barnardi Leloup, 1981

Schwabe, Enrico, 2004, The Polyplacophora (Mollusca) collected during the First International Marine Biodiversity Workshop for Rodrigues (western Indian Ocean), with the description of a new species, Journal of Natural History 38 (23), pp. 3143-3173 : 3150-3156

publication ID	https://doi.org/ 10.1080/00222930410001695114
persistent identifier	https://treatment.plazi.org/id/03B187BA-FFB9-D62F-FE78-FC05459FFE9F
treatment provided by	Felipe
scientific name	Callistochiton barnardi Leloup, 1981
status

Treatment

Callistochiton barnardi Leloup, 1981 View in CoL

( figures 5 View FIG , 6 View FIG , 17C View FIG )

Callistochiton (Callistassecla) barnardi Leloup, 1981a: 10 View in CoL , text figure 4 View FIG , pl. 1, figure 7 View FIG .

Callistochiton barnardi: Kaas and Van Belle, 1994: 142 View in CoL , figure 57; 1998: 28.

? Callistochiton barnardi ‘ Ashby, 1931 View in CoL ’; Glayzer et al., 1984: 324.

Type. Holotype ( MNHN) [not seen].

Type locality. Madagascar, Tuléar , Grand Récif .

Material examined. 2 spms, 4.2 6 2.6 mm (pd), 4.8 6 3.2 mm: RDS 31, Grand Pate´, 19 ‡ 39.388 ’ S, 63 ‡ 25.130 ’ E, 13–15 m, coral rubble, leg. N. Bruce; 5 spms, 3.0 6 1.9 mm, 2.9 6 2.0 mm, 2.3 6 1.6 mm, 2.6 6 1.8 mm, 1.7 6 1.0 mm: RDS 52, Grand Pate´, 19 ‡ 39.307 ’ S, 63 ‡ 24.950 ’ E, 17 m, leg. N. Bruce; 1 spm, 4.1 6 2.2 mm: RDS 35, Grand Pate´, 19 ‡ 39.047 ’ S, 63 ‡ 26.381 ’ E, 21.5 m, coral rubble, leg. N. Bruce.

Description

The elongate oval animal is sculptured by bold, broad radial ribs in the head valve, the lateral areas as well as the postmucronal area of tail valve ( figure 17C View FIG ). The pleural areas and the antemucronal area show longitudinally arranged ribs. The jugal area is smooth.

Tegmentum. Head valve more than semicircular, with wide V-shaped posterior margin, unnotched in middle. Head valve with nine strong radial ribs, crossed by fine growth marks ( figure 5A View FIG ). Second valve shows six longitudinally arranged ribs on both sides of smooth jugum. They range from the two ribbed, raised lateral areas, anteriorwards to the margin of the plates ( figure 5B View FIG ). In older specimens all ribs are more or less granulated. Tail valve semicircular, anterior margin straight, mucro slightly elevated, forward directed and almost central. Antemucronal area sculptured like pleural areas. Straight slope of postmucronal area rather steep, with eight radially arranged ribs, similar to those of head valve ( figure 5C, D View FIG ).

Articulamentum. Inner layer thin and translucent white. Apophyses short and triangular in second valve and wide trapezoid in tail valve. A shallow, partly pectinated jugal plate connects the apophyses. Slit formula: 8/1/9. Slits deep, slit rays present in all valves. Teeth smooth, broad and sharp.

Perinotum. Dorsally covered with round-topped, oval scales, 55–93 M m in width, sculptured with 11–13 radial ribs ( figure 6A–E View FIG ). Margin with three types of girdle elements. Short (74 6 15.9 M m), ribbed spicules, which are contorted ( figure 6B View FIG ). Slender, smooth needles (67 6 5.5 M m) ( figure 6D View FIG ). Small, conical, calcareous spicules (19 6 5 M m), the so-called tips of clapper (see Fischer et al., 1988) ( figure 6C, E View FIG ). Ventral side of girdle covered with oval to rectangular, smooth scales, measuring 30.2–38 6 13.8–19 M m ( figure 6F View FIG ).

Radula. Consists of 42 teeth rows, of which 30 are mineralized. Central tooth extremely slender, parallel-sided and has a sharp, forward-directed blade, slightly notched in middle. First lateral tooth much wider than central one, with an extension in the basal half ( figure 5E, F View FIG ). Its blade is laterally enrolled. Major lateral tooth has a long, slightly keeled shaft, which bears a bilobed blade. Innermost denticle of the blade largest. Large, spoon-like blade of major uncinal tooth supports the head of the major lateral tooth.

Ctenidia . Ctenidia are arranged holobranchially and abanally. There are 20 ctenidia on the left and 18 on the right side.

Comments

The identification of this species is based on the illustrations of the original description and figures by Kaas (1986). The material conforms well with these illustrations. The specimens mentioned here are similar to seven specimens of Callistochiton viaderi Leloup, 1941 from the Viader collection ( NMW.Z.2000.083.03113). Kaas (1979) considered this species a junior synonym of Chiton barnardi Ashby, 1931 . The holotype of the latter ( SAMC A5331) was not studied, but based on Ashby’s (1931) description, the placement in the genus Chiton Linnaeus, 1758 seems correct. He wrote (1931: 47): ‘ … teeth thick with bluntly serrate edge, grooved outside, smooth inside … The spongy eaves, the serrate extension of the articulamentum across the jugal sinus, and the peculiar truncated tail valve suggest possible justification for subgeneric separation … I leave it under the genus Chiton ’. One of the examined specimens from the Viader collection (no types) shows smooth teeth and seems to be correctly placed within the genus Callistochiton . A careful study of both types is needed, to clarify if Callistochiton viaderi is conspecific with Chiton barnardi .

The occurrence of Callistochiton barnardi ‘ Ashby, 1931 ’ in the Arabian Gulf, as reported by Glayzer et al. (1984), is probably a misinterpretation of a northern Indian Ocean Callistochiton .

Family CHITONIDAE Rafinesque, 1815

Lucilina Dall, 1882: 289 View in CoL

Type species: Chiton confossus Gould, 1846 ~ Chiton lamellosus Quoy and Gaimard, 1835 , by subsequent designation, Pilsbry, 1893: 210.

Lucilina indica (Leloup, 1981)

( figures 7 View FIG , 8 View FIG , 17G, H View FIG )

Tonicia indica Leloup, 1981a: 40 View in CoL ; figure 22, pl. 2 figure 7 View FIG , pl. 3 figure 1 View FIG ; Kaas, 1986: 18 (as synonym of Tonicia (Lucilina) carnosa Kaas, 1979 View in CoL ); Kaas and Van Belle, 1998: 94; Slieker, 2000: 146.

? Tonicia (Lucilina) carnosa: Kaas, 1985a: 331 View in CoL (non Kaas, 1979); Drivas and Jay, 1998: 32, figure 3 View FIG .

Type. Holotype ( MNHN).

Type locality. Madagascar, Tuléar .

Material examined. 1 spm, ca 22.1 6 11.2 mm (curled): Passe Demi, 19 ‡ 42.104 ’ S, 63 ‡ 17.570 ’ E, 17–18 m, leg. N. Bruce; 2 spms, ca 1.5 6 1.2 mm, ca 2.8 6 1.8 mm (both curled): RDS 52, Grand Pate´, 17 m, leg. N. Bruce; 1 spm, 5.8 6 3.5 mm: 3 spms, ca 5.2 6 3.5 mm, ca 4.4 6 2.7 mm, (pd), ca 3.7 6 3 mm (all curled): RDS 31, Grand Pate´, 13–15 m, leg. N. Bruce; 2 spms, 5.5 6 3.3 mm, 8.5 6 5.3 mm: RDS 32, Grand Pate´, 17.5 m, leg. N. Bruce.

Description

Animal elongate-oval. Colour variable but generally beige ( figure 17G, H View FIG ). Tegmentum smooth with fine longitudinally arranged ribs in pleural areas. Large lenses of macroaesthetes are arranged along the diagonal ridge of lateral areas, head valve and postmucronal area. The girdle appears naked, but is densely beset with microscopic spicules.

Tegmentum. Head valve semicircular with a wide V-shaped posterior margin ( figure 7A View FIG ), sculptured with 40 granulated, radially arranged ribs. Ocelli are situated between the ribs. Second valve with smooth, wedge-shaped jugum ( figure 7B View FIG ). Pleural areas show 11 weakly granulated, longitudinal ribs (on each side of the jugum), extending from diagonal ridge to anterior margin of valve. Lateral areas are elevated. Nodules of anterior (diagonal) ridge is built by posterior-directed ends of longitudinal ribs of pleural areas. Between these distinct ribs a rather smooth wedge-shaped region contains inward-directed lenses of macroaesthetes. Apex of intermediate valves protruded. Tail valve semicircular; mucro elevated, forward directed and slightly central ( figure 7C View FIG ). Postmucronal area with rather steep slope and sculptured by ca 30 fine radial ribs and concentrical growth marks ( figure 7D View FIG ). Antemucronal area sculptured like central areas of intermediate valves.

Articulamentum. Thick and white, forming large apophyses, triangular in valve II and trapezoid in tail valve. Slit formula is: 8/1/12, slits deep and slit rays present in all valves. Teeth of insertion plates broad and pectinated outside. The jugal sinus is finely pectinated.

Perinotum. Wide and fleshy, and appears naked. Dorsally finely covered with very small (23.4 6 12.3–15.3 M m), calcareous spines with five strong, longitudinal radial ribs and a smooth, blunt tip ( figure 8B, D View FIG ). The margin has larger (57.3 6 16.4 M m), flat, elongate, spines with five ribs ( figure 8C View FIG ). Dorsally, very small (9.7–13.9 6 2.4 M m), smooth, slightly curved spines occur randomly. Ventrally the girdle is densely paved by broad oval to rectangular scales, measuring 20.4–24.1 6 18.5–24.1 M m. They are distally finely ribbed with seven or eight ribs ( figure 8E, F View FIG ).

Radula. The disarticulated specimen has 35 teeth rows, of which 23 rows are mineralized. Central tooth slender with a squarish base, a sharp front keel and a round-topped single blade. First lateral tooth much larger than central one, the blade is inward and longitudinally directed with a single spoon-like blade, which shows a shallow bay in the middle ( figure 8A View FIG ). Second lateral very large, with a broad rectangular shaft, and a broad blade with four large denticles, the two inner ones are largest. A very large and broad spatulate uncinal tooth supports the head of the second lateral tooth ( figure 7F View FIG ).

Ctenidia . A 5.8 mm long specimen has 20 abanal and holobranchial ctenidia on both sides of the foot.

Comments

The identification of Lucilina indica is based on a good picture of the holotype ( MNHN). Kaas (1986: 18) considered Leloup’s species conspecific with Lucilina carnosa ( Kaas, 1979) . However, examination of the holotype of the latter (NM T. 2395, Moll. No. H2576; 21.5 6 11.1 mm; dry), has shown that this specimen, compared with the largest examined specimen of L. indica , shows significant differences. The nearly central mucro in L. indica , in comparison with the higher elevated and more posteriorly directed mucro in L. carnosa , results in a different shape of the tail valve. The intermediate valves show a broader wedge-shaped jugum in L. carnosa , resulting in shorter longitudinal ribs in the pleural areas. In addition, the general valve surface is stronger sculptured in L. carnosa . The tegmental sculpture of the 8 mm long holotype of L. indica is somewhat coarser than that of the 8.5 mm long specimen from RDS 32, but both agree in general appearance. The growth series examined, however, shows a reduction of the coarse granules to a weaker sculpture with increasing length. It cannot be excluded that the holotype of L. carnosa is only an unusual coarse specimen of L. indica . Since the Rodrigues material examined is more similar to the holotype of Leloup’s species than to the species described by Kaas, it is identified as Lucilina indica .