Cryptoplax burrowi (E.A. Smith, 1884 )

Dell’Angelo, Bruno, Gori, Sandro, Baschieri, Leonardo & Bonfitto, Antonio, 2010, Chitons (Mollusca, Polyplacophora) from the Maldive islands, Zootaxa 2673 (1), pp. 1-38 : 26-32

Cryptoplax burrowi (E.A. Smith, 1884)

( Figures 11A–L , 12R–X , 13O–R , 14B–C )

Chiton (Chitonellus) burrowi E.A. Smith 1884: 85 .

Cryptoplax burrowi ; Iredale & Hull 1927: 96, pl. 11, figs 13, 31, 32; Leloup 1940: 15, fig. 5, pl. 3, fig. 3 (bibliography and synonymy); Kaas 1979: 877; Kaas et al. 1998: 189; Kaas & Van Belle 1998: 36; Slieker 2000: 54, pl. 15, fig. 11; Gowlett-Holmes 2001: 46; Schwabe 2005: 54, pl. 2, fig. 12; Burghardt et al. 2006: 30.

Non Cryptoplax burrowi ; Haddon 1886: 42, pl. 3, figs 11 a–m; Pilsbry 1893: 54, pl. 9, figs 6–10 (fide Iredale & Hull 1927: 97), referring to a form of Cryptoplax elioti Pilsbry, 1901 .

Type: Syntypes NHM 1881.11.1.100 (1 specimen), NHM 1992053 (4 specimens) (fide Gowlett-Holmes 2001: 46).

Type locality: Port Molle , Queensland, Australia .

Material examined: M07: 1 spm (length 11.7 mm, curled, Figs 12R–S ); M13: 4 valves (2 intermediate and 2 tail); M20: 2 valves (1 head and 1 intermediate); M65: 3 valves (2 intermediate and 1 tail); MLD02A: 4 valves (1 head and 3 intermediate); MLD03A: 2 valves (1 head and 1 intermediate); LB05: 14 valves (8 head and 6 intermediate); Indonesia ( NW Sulawesi, Bunaken National Park, W Bunaken Id): 1 spm ( ZSM Mol 20033081, leg. E. Schwabe 16/07/2003, length 25.4 mm, Fig. 12T ).

Description: The living specimen ( Figs 12R–S ) is strongly curved. The first four valves are in contact, valve v is near valve iv, and the following valves with spaces in between. It is difficult to measure the distance between the valves, also because valves vii and viii are in the curled extremity, but the distance between valves vi and vii is the widest, and with a greater approximation the distances can be estimated as 1.3 mm between valves v–vi, 2.2 mm between valves vi–vii and 1.5 mm between valves vii–viii. The valves are eroded, without visible sculpture. Perinotum wide and velvety, colour greenish brown with whithish spots. Two types of dorsal scales are present ( Figs 11K–L ), the first more elongate, flat, rounded at the top and sculptured with 9–10 large longitudinal ribs, the second more numerous and shorter, cylindrical and rounded at the top, strongly sculptured with longitudinal striae. The marginal fringe shows cylindrical, straight spicules ( Fig. 11I ), and ventrally there are rectangular flat spicules ( Fig. 11J ), finely longitudinally striated.

The 29 separate valves have a tegmental coloration of reddish-brown to whitish. Head valve horseshoeshaped ( Fig. 11A ), the tegmentum occupying a large amount of the whole valve, the anterior margin is rounded, while the posterior is straight. Valves ii roughly pentagonal in outline. Valves iii–vii narrow, spindleshaped ( Fig. 11C ) [as known, in Cryptoplax intermediate valves can differ from each other in layout and dimension ( Pilsbry 1901)]. Tail valve spindle-shaped with the insertion lamina well visible around the tegmentum ( Fig. 11F ), mucro terminal.

The sculpture consists of a smooth and parallel-sided jugal area and of 3–5 rows of elongate granules in latero-pleural areas, that aim to become indistinct towards the anterior valve margin. The granules in lateropleural areas show a megalaesthete in a more or less central position, surrounded by numerous micraesthetes, which are irregularly distributed ( Fig. 11H ).

Articulamentum white, strongly developed. Intermediate and tail valves with elongate apophyses, which are connected by a jugal lamina in the tail valve. Slit formula 3/0/0.

Remarks: This species has a complex taxonomic history. It was described by E.A. Smith (1884) on the basis of a single specimen from Port Molle (Queensland, Australia), without illustrations, as a new name (nomen novum) for Chitonellus larvaeformis Reeve, 1847 , not Burrow, 1815. He regarded the figure given by Reeve for his Chitonellus larvaeformis as sufficiently exact to represent his species. The subsequent reports of Haddon (1886: 42, pl. 3, Figs 11a–m ) and Pilsbry (1893: 54, pl. 9, Figs 6–10 ) are erroneous, referring instead to a form of Cryptoplax elioti Pilsbry, 1901 (fide Iredale & Hull 1925: 107; 1927: 97). If this interpretation is correct, following Iredale & Hull (1925, 1927), the type material in the NHM should not be of C. burrowi , because when Haddon reported upon the Challenger Polyplacophora he reproduced drawings made by E.A. Smith from specimens in the NHM. Good descriptions of the species were subsequently given by Nierstrasz (1905) and Leloup (1940), who established the synonymy with C. hartmeyeri Thiele, 1911 and C. mjöbergi Bergenhayn, 1933 , a decision which was followed by subsequent authors ( Kaas & Van Belle 1998; Gowlett- Holmes 2001). To our knowledge, no other description of the species was given after Leloup (1940).

We examined and illustrate for comparison the type material of Cryptoplax burrowi present in NHM:

- NHM 1881.11.1.100, syntype, detached valves (“body in alcohol” reported in the label illustrated, Fig. 14C , but not present in the material examined), Coll. Coppinger, Port Molle, Queensland, 12-20 fms. 12 valves are present, 3 head and 9 intermediates, there are not tail valves ( Figs 13 O-R)

- NHM 1992 053, syntypes, 4 spm, H. Cuming colln., Port Adelaide, S. Australia (figured in Reeve, 1847, sp. 3, pl. 1, fig. 3 as C. larvaeformis ), length respectively 56.4 mm ( Fig. 12U ), 47 mm ( Fig. 12W ), 45.1 mm ( Fig. 12X ) and 38.5 mm ( Fig. 12V ).

TEXTFIGURE 1. Cryptoplax burrowi , girdle elements (from Leloup, 1940: figs 5 A i - 5 A iv)

This material does not completely agree with the living specimes from the Maldives Islands, mainly in the girdle colour (yellowish brown, instead of greenish brown in our specimen), and in the different disposition of the valves, the first four in contact, valve v well separated from iv (much more that in our specimen), the distances between valves v – vi and vi – vii are the widest and similar, the distance between the valves vii-viii about the half than between the valves iv – v.

The characters of our material agree with the more extended description given by Leloup (1940, pp. 22- 23), that also presented a table with the main characters of C. burrowi (including the synonyms C. hartmeyeri and C. mjöbergi ) compared with C. elioti and C. dupuisi Ashby, 1931 . We report for completeness fig. 5 of Leloup 1940 (textfig. 1) illustrating the girdle elements.

For comparison a specimen of Cryptoplax burrowi from Indonesia ( Fig. 12T ) was examined. It has a length of 25.4 mm, the first four valves are in contact, the valve v is near the valve iv (but not so close as in specimen from Maldives), and the following valves with spaces in between. In this specimen the distance between valves vi–vii (5 mm) is also the widest, while there are 3.7 mm between valves v–vi, and 2.6 mm between valves vii–viii (always with a large approximation, but more acurate than for the curled Maldive specimen).

The sculpture of the separate valves agrees with the description given by Leloup (1940: 17), and the layout of the valves agrees with the drawings given by Nierstrasz (1905: Fig. 146).

Determination of the specimens from the Maldives Island is very difficult, considering also the very complex taxonomical history of Cryptoplax burrowi , and the doubts regarding the type material present in the NHM. Additional material to study and examination of the type material of the other Cryptoplax species will be necessary, and this is outside the scope of this work. We preliminarily assign the specimens to Cryptoplax burrowi .

Distribution: Cryptoplax burrowi is a species commonly collected in the intertidal, living between and under dead corals and under stones. It is known from Australia (W. Australia, Queensland), Christmas Island, Indonesia (Sulawesi, Lombock, Damar, Banda), Philippines (Sulu Archipelago) and Maldive Islands.

Figures

FIGURE 6A–O, Lucilina sp., Maldive. A–G, juvenile living specimen, M07. A, dorsal view of the complete specimen. B, close-up of the head valve. C, close-up of the tail valve. D, ocelli in the lateral area of intermediate valves. E, close-up of Fig. D, showing the ocelli. F, lateral view of the tail valve. G, perinotum elements in situ. H–J, head valve, MLD02A, dorsal, lateral and frontal views, respectively. K–L, intermediate valve, M13. K, dorsal view. L, detail of the sculpture. M–O, tail valve, M65, dorsal, lateral and posterior views, respectively. Scale bars 1 mm: A, K; 500 µm: H–J, L–O; 100 µm: B–D, F; 10 µm: E, G.

FIGURE 7A–D, Acanthochitona penicillata (Deshayes, 1863), Maldive. A–C, intermediate valve, MLD02A. A, dorsal view. B–C, granules, dorsal and lateral views, respectively. D, dorsal view of tail valve, LB05,. E–G, Acanthochitona sp., LB05, intermediate valve. E, dorsal view. F–G, granules, dorsal and lateral views. H–Q, Craspedochiton cf. laqueatus (Sowerby, 1842), Maldive, valves dismounted from living specimen, M59. H–J, head valve. H, dorsal view. I, detail of the sculpture. J, frontal view. K–M, intermediate valve. K, dorsal view. L, frontal view. M, detail of the sculpture. N–Q, tail valve. N, dorsal view. O, ventral view. P, lateral view. Q, posterior view. Scale bars 1 mm: H, J–L, N–P; 500 µm: A, D, Q; 100 µm: E, I, M; 50 µm: B, C, F, G.

FIGURE 8A–J. Craspedochiton cf. laqueatus (Sowerby, 1842), Maldive, living specimen, M59. A–D, radula. A, general view of the radula. B, blades of the second lateral tooth. C, close-up of the central region. D, detail of the first lateral teeth. E–J, girdle elements, in situ. E, dorsal tuft of needles. F, dorsal spines. G, marginal spicules. H, ventral scales in the anterior portion. I, ventral scales in the middle portion. J, ventral scales in the posterior portion. Scale bars 100 µm: A, E, G; 50 µm: B–D, H–J; 10 µm: F.

FIGURE 9A–G. Craspedochiton cf. laqueatus (Sowerby, 1842), valves, Maldive, MLD02A. A–C, head valve. A, dorsal view. B, detail of the sculpture. C, posterior view. D–G, intermediate valve. D–E, dorsal and frontal views, respectively. F–G, detail of the sculpture of the pleural areas. H–K, Craspedochiton sp., tail valve, Maldive, M65. H, dorsal view. I, detail of the right side. J, detail of the insertion lamina teeth. K, lateral view. Scale bars 1 mm: A, D, E, H, K; 500 µm: C, I, J; 100 µm: B, F, G.

FIGURE 10A–F, Craspedochiton laqueatus (Sowerby, 1842), NHM type material, Philippines, Mindoro, Calapan, not coated. A–C, E–F, valves detached from the paralectotype NHM 1988071/2. A–B, head valve, dorsal and lateral views, respectively. C, intermediate valve (ii), dorsal view. E–F, tail valve, dorsal and lateral views. D, hyponotum scale in situ, from the paralectotype NHM 1988071/3-5, length 11.3 mm (Fig. 12Q). Scale bars 1 mm: A–C, E–F; 10 µm: D.

FIGURE 11A–L, Cryptoplax burrowi (E.A. Smith, 1884), Maldive. A–B, head valve, MLD02A. A, dorsal view. B, detail of the sculpture. C–E, intermediate valve, M65. C, dorsal view. D, detail of the sculpture. E, lateral view. F–H, tail valve, M65. F, dorsal view. G, lateral view. H, detail of the sculpture. I–L, living specimen, M07, girdle elements in situ. I, marginal spicules. J, ventral spicules. K–L, dorsal scales. M–O, Cryptoplax sykesi Thiele, 1909, intermediate valve, Maldive, M13. M, dorsal view. N, lateral view. O, detail of the sculpture. Scale bars 1 mm: C, E–G, N; 500 µm: A, M; 100 µm: B, D, H, I, K, L, O; 50 µm: J.

FIGURE 12A, Parachiton hylkiae mauricejayi Schwabe, 2002, living specimen, Maldive, LB03B, length 12.8 mm. B, Ischnochiton albinus Thiele, 1911, living specimen, Maldive, M13, length 5.2 mm. C, Ischnochiton feliduensis E.A. Smith, 1903, Maldive, Felidhoo Atoll, Holotype, NHM 1903.9.17.25, length 6 mm. D, Tegulaplax hululensis (E.A. Smith, 1903), living specimen, Maldive, M28, length 10.5 mm. E–F, Callochiton sp., S. Nilandu Atoll, Maldive, NHM 1903.4.11.71 (living specimen collected by J.S. Gardiner), length 6.6 mm. G, Lucilina sp., living specimen, Maldive, M07, length 4 mm. H, Lucilina indica (Leloup, 1981), holotype (MNHN), Madagascar, Tuléar, length 8 mm. I, Acanthopleura miles (Carpenter in Pilsbry, 1893), living specimen, Japan, Okinawa, Sesoko Island, length 29.2 mm. J, Schizochiton incisus (Sowerby, 1841), living specimen, Indonesia: inside lagoon of Woka Island, off South Halmahera, 1°2.02’S, 128°13.97’E (ZSM Mol 20052075), length 40 mm. K, Acanthochitona penicillata (Deshayes, 1863), living specimen, Maldive, MLD04A, length 6.5 mm. L, Craspedochiton cf. laqueatus (Sowerby, 1842), living specimen, Maldive, M59, length 13.5 mm. M–Q, Craspedochiton laqueatus (Sowerby, 1842), NHM type material, Philippines, Mindoro, Calapan. M, lectotype (NHM 1988071/1), length 17.4 mm. N, paralectotype (NHM 1988071/2), length 17.5 mm. O–Q, paralectotypes (NHM 1988071/3-5), length respectively 16, 13.2 and 11.3 mm. R–S, Cryptoplax burrowi (E.A. Smith, 1884), living specimen, Maldive, M07, length ca. 11.7 mm. T, Cryptoplax burrowi (E.A. Smith, 1884), living specimen, Indonesia, ZSM Mol 20033081, length 25.4 mm. U–X, Cryptoplax burrowi (E.A. Smith, 1884), NHM 1992 053, syntypes, H. Cuming colln., Port Adelaide, S. Australia, length respectively 56.4, 38.5, 47 and 45.1 mm.

FIGURE 13A–B, Callochiton sp., S. Nilandu Atoll, Maldive, NHM 1903.4.11.71 (living specimen collected by J.S. Gardiner), close-up of the head and tail valves. C–H, Lucilina carnosa (Kaas, 1979), valves, Maldive. C–D, head valves, M13, showing differences in the number of ocelli rows, widths 3 and 3.1 mm, respectively. E, intermediate valve, M13, width 3.5 mm. F, tail valve, M13, width 3.3 mm. G–H, anomalous tail valve, dorsal and posterior views, respectively, M20, width 3.2 mm. I–K, Lucilina sp., valves, Maldive. I, head valve, M13, width 3.1 mm. J, intermediate valve, M20, width 4.7 mm. K, tail valve, M65, width 3.4 mm. L–M, Craspedochiton cf. laqueatus (Sowerby, 1842), head and intermediate valves, Maldive, M65, widths 5.7 and 5.2 mm, respectively. N, Craspedochiton sp., tail valve, Maldive, M65, width 5.8 mm. O–R, Cryptoplax burrowi E.A. Smith, 1884, NHM 1881.11.1.100, syntype, detached valves, coll. Coppinger, Port Molle, Queensland. O–P, intermediate valve, length 4 mm, dorsal and right lateral views, respectively. Q, intermediate valve, length 4.2 mm. R, head valve, length 3.5 mm.

FIGURE 14A–C, NHM labels, with informations on type material. A, Chiton laqueatus Sowerby, 1842, 5 specimens (lectotype and 4 paralectotypes), NHM 1988071/1-5. B–C, Cryptoplax burrowi E.A. Smith 1884. B, NHM 1992 053, syntypes, 4 specimens, H. Cuming colln., Port Adelaide, S. Australia. C, NHM 1881.11.1.100, syntype, detached valves, coll. Coppinger, Port Molle, Queensland. D, NHM label of Callochiton platessa Gould, 1846, S. Nilandu Atoll, Maldive, NHM 1903.4.11.71, living specimen collected by J.S. Gardiner (considered as Callochiton sp. in this work).