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The Conus Biodiversity Website

CATALOGUE OF RECENT AND FOSSIL CONUS

  Conus magus Linnaeus, 1758.

Range: Indonesia to Japan and to the Marshall Is., Wallis and Fiji. Most reports from the central and western Indian Ocean are doubtful; probably Madagascar.

Description: Moderately small to large, moderately solid to moderately heavy; relative weight varies in specimens of similar size by 50% within the same population. Last whorl narrowly conoid-cylindrical to conoid-cylindrical, or narrowly conical to ventricosely conical, sometimes narrowly ovate to ovate; outline almost straight to evenly convex. Aperture variably wider at base than near shoulder. Shoulder angulate to subangulate. Spire of low to moderate height, outline concave to convex. Larval shell of 1.75-2.0 whorls, maximum diameter 0.7-0.8 mm. First 3-8 postnuclear whorls tuberculate. Teleoconch sutural ramps flat to often concave in last whorl, with 1-2 increasing to 4-7 spiral grooves; latest ramps often with punctate grooves, sometimes only 2 of them distinct. Last whorl usually with weak spiral ribs at base and finer wrinkled elevations above. Closely set axial threads sometimes produce a minute granulation on basal ribs. In specimens described as C. cernohorskyi (Pl. 20, Fig. 18), spiral ribs and granules stronger, occasionally extending to shoulder.

Shell Morphometry
  L 30-94 mm
  RW 0.10-0.83 g/mm
     (L 30-89 mm)
  RD 0.47-0.69
     (0.47 form epistomium; 0.57-0.69 form cernohorskyi)
  PMD 0.72-0.91
  RSH 0.05-0.19

Ground colour sometimes blue or pink, usually white but often grading to yellow or tan. Last whorl with one adapical and one abapical spiral colour band, dashed and dotted spiral lines and irregular axial streaks, flames or blotches. Colour bands and axial markings pink, orange, olive, greenish to bluish grey or shading from yellow to dark brown or black; spiral bands and axial markings either of the same or different colour. Bands vary considerably in width, ranging from completely absent to leaving remnants of ground colour only at centre, shoulder and base; axial markings varying considerably either set off from or merging with spiral bands. Spiral rows of brown to black dots and dashes vary from absent to numerous and pronounced, often with intermittent light dots and dashes. Pattern ranges from monochrome to multicoloured, heavily patterned shells intergrade with immaculate white shells. Larval whorls and a few of adjacent postnuclear sutural ramps white to beige, pink or brown; colour may vary considerably within a population. Late sutural ramps sparsely to heavily marked with radial lines, streaks or blotches, usually matching pattern of last whorl in one or two of its major colours. Aperture white, occasionally pale pink or with brown blotches.

Periostracum light olive to brown, thin, translucent to opaque, smooth or with fine close-set spiral and axial ridges; spiral elevations often finely tufted both on last whorl and spire.

Dorsum of foot white, variably mottled with brown rnedially; marginal zones often pale orange to light brown, dotted with white and edged with yellow or orange anteriorly; a large transverse black blotch on anterior part, sometimes divided into 3 smaller blotches or reduced to one central blotch; a dotted grey pre-marginal line varies from prominent to absent, often broader at posterior end. Occasionally, dorsum of foot pale pink to pale orange, with typical black pattern. Sole of foot immaculate pink, or white mottled with brown. In some specimens, entire foot mottled tan and brown, without typical black pattern on dorsum. Rostrum white mottled with brown; tip usually immaculate. Tentacles white, mottled with brown or pale orange dorsally; tip often brown. Siphon white, often grading to pink dorsally, mottled with brown and grey; mottling usually sparse distally and absent from the tip (Cemohorsky, 1964; Chaberman, pers. comm., 1981; Kohn, unpubl. observ.; Estival, unpubl. observ.; Pearson, unpubl. observ.). (Pl. 75, Fig. 36; Pl. 79, First row, right; Fourth row, left). Specimens with shell larger than 10.5 mm with relatively large radular teeth with a long shaft terminating in 2 short adapical barbs and an additional posterior barb with a recurved tip; both serration and a basal spur are absent. Juveniles smaller than 9 mm have relatively short teeth with a stout shaft lacking armature. Specimens of shell length 9- 10.5 mm possess intermediate radular teeth (small, with a stout shaft and adult armature). Length of radular teeth varies from 0.06 to 0.1 x shell length, with largest teeth observed in Fiji specimens (Cernohorsky, 1964; James, 1980, Nybakken & Perron, 1988). Radular studies by Rolán proved frauenfeldi to have teeth identical to those of typical C. magus from Philippines (G. Raybaudi, in press).

Intertidal and upper subtidal; juveniles sometimes in 100 m and more. A sand-dweller on coral reef and in sheltered bays, often beneath rocks and dead coral (Cernohorsky, 1964; Kohn & Nybakken, 1975; Tirard, pers. comm., 1989; Richards, pers. comm., 1989). Form frauenfeldi on muddy sand in about 5 m, at the ocean-side of coral reef (Sumatra; Huber, pers. comm., 1992). C. magus becomes active at night and preys upon fishes when shell length is at least 9 mm. Smaller juveniles feed on syllid pol ychaetes (Nybakken & Perron, 1988). The change in diet is associated with a change in in morphology of radular teeth (see above). Venom of adult specimens highly toxic to fishes and small mammals, variably toxic to worms and gastropods (Endean & Rudkin, 1965). Egg diameter of about 560 µm predicts completely benthic development (Perron & Kohn, 1985).

Habitat and Habits: Intertidal and upper subtidal; juveniles sometimes dredged from 100 m and more. A sand-dweller on coral reef and in sheltered bays, often beneath rocks and dead coral (Cernohorsky, 1964; Kohn & Nybakken, 1975; Tirard, pers. comm., 1989; Richards, pers. comm., 1989). C. magus becomes active at night and preys upon fishes when shell length is at least 9 mm. Smaller juveniles feed on syllid polychaetes (Nybakken & Perron, 1988). The change in diet is associated with a change in in morphology of radular teeth (see above). Venom of adult specimens highly toxic to fishes and small mammals, variably toxic to worms and gastropods (Endean & Rudkin, 1965). Egg diameter of about 560 fm predicts completely benthic development (Perron & Kohn, 1985).

Discussion: C. magus is often very similar to C. consors and sometimes similar to C. fischoederi. C. magus and C. consors often cannot be distinguished by shape, sculpture or colour pattern of the shell. C. consors is usually larger (51-118 mm), and it differs in its multispiral (about 3 whorls) larval shell, as would be expected in a species with a smaller egg and planktonic larva. Shells of C. consors with beige to brown larval shells can be separated for similar shells of C. magus by this character. In addition, the spiral ribs on the sutural ramps are usually weaker in C. consors. Very close to C. consonr in colour pattern is C. magus form raphanus, but the latter can easily be distinguished by its pink apex and yellow and olive dots on the adjacent postnuclear sutural ramps. Specimens of C. fischoederi with a reduced reticulate pattern resemble similarly patterned forms of C. magus. The latter shells are less ventricose and have a more angulate shoulder; their pattern shows no remnants of a meshwork and tents. For comparison with C. gubernator, see the Discussion of the latter species. In Indonesia and Philippines, C. magus is characterized by a remarkable conchological divergence between separate populations, while the species is rather uniform from New Caledonia to Queensland. Within the same population, C. magus may be either largely uniform or fairly variable in shell morphology. The taxonomic status of most nominal species assigned to C. magus therefore remains hypothetical and disputed. We consider the following as forms: - C. ambaroides (Pl. 20, Fig. 30): Last whorl reddish brown, with white axial flecks at centre; based on a subadult specimen. - C. assimilis (Pl. 20, Fig. 12): Last whorl ventricosely conical. Known from various localities. - C. carinatus (Pl. 20, Fig. 15): Last whorl conical, conoid-cylindrical or ventricosely conical. Ground colour white to tan. Colour pattern comparatively uniform, consisting of spiral bands and lines and axial streaks in various shades of brown. Known from Philippines (Sulu Sea, S. Luzon). - C. cernohorskyi (Pl. 20, Fig. 18): Moderately small to medium- sized, moderately solid. Last whorl usually ventricosely conical; surface comparatively rough. Larval whorls consistently pink. Although this variant attains broader last whorls than all other forms of C. magus, the overlap in relative diameter allows no clear separation; neither do the differences in surface sculpture. Known from various Philippine localities. We consider it a infrasubspecific form but perhaps it is a sibling species. C. cernohorskyi may be a synonym of C. metcalfii. - C. circae: Similar to C. raphanus in shell shape, but last whorl often less inflated below shoulder and grading to ventricosely conical. Known from New Caledonia and the Solomon Islands. - C. consul (Pl. 20, Figs. 13, 14): Essentially similar to C. assimilis and C. fulvobullatu. - C. epistomium (Pl. 20, Fig. 20): Last whorl narrowly conoid-cylindrical; pattern similar to that of C. raphanu. - C. frauenfeldi (Pl. 45, Figs. 22-25): In small specimens, last whorl conical to ventricosely conical. Pattern consists of blackish-brown axial flames and dotted or dashed spiral lines; spiral lines sometimes sparse, often with intermittent white dots and dashes. In E. Sumatra shells almost matching the type specimens of C. frauenfeldi occur and also intergrade with typical C. magus. They differ from the type specimens of C. frauenfeldi in an orange to brown instead of white to pink apex; however this difference is in the range of variability of C. magus. We therefore consider C. frauenfeldi a form of C. magus; the type locality "Madagascar" needs to be confirmed. - C. fulvobullatus (Pl. 20, Fig. 11): Essentially similar to C. assimilis. - C. metcalfii (Pl. 20, Figs. 17, 19): Relatively small and stout. Last whorl with yellow and dark brown to black blotches. Probably the same variant as C. cernohorskyi. - C. raphanus (Pl. 20, Figs. 21 ,22): Shell relatively solid. Last whorl conical, usually more inflated below shoulder in adult specimens than in other forms of C. magus. Ground colour white. Pattern consists of yellow to light brown spiral bands, brown axial streaks of varying prominence, and dotted yellow to brown spiral lines either on entire last whorl or restricted to colour bands. Known from various localities in Indonesia and Philippines. - C. rollandi (Pl. 20, Fig. 28): Last whorl white with red-brown flames and axial streaks. - C. signifier (Pl. 20, Fig. 25): Last whorl tinged with reddish brown, with white flecks at centre and below shoulder. In Fiji, this colour form lives sympatrically with other colour variants. - C. tasmaniae: Last whorl comparatively narrow, with brown axial streaks. - C. ustulatus (Pl. 20, Fig. 26): Last whorl with closely set spiral ribs from base to shoulder and 2 broad pale yellow spiral bands. Known from the Louisiade Archipelago (Solomon Sea) and Palawan, Philippines. - Specimens from Papua New Guinea, sometimes erroneously called "C. melancholicus Lamarck" (see Marsh & Rippingale, 1964) (Pl. 20, Figs. 7-9): Last whorl narrowly ovate to ovate, with light to dark brown axial streaks and flames. Aperture comparatively wide. These specimens may represent a geographic variant or a closely related distinct species. C. melancholicus Lamarck is a nomen dubium (Kohn, 1981). We regard the following as synonyms of C. magus rather than forms: C. caesius, C. fucatus (Pl. 20, Fig. 31) (juvenile type specimens), C. borneensis, and C. epistomioides (Pl. 20, Fig. 29) (based on a subadult specimen).

Range Map Image

C. magus range map

This section contains verbatim reproductions of the accounts of 316 species of Conus from the Indo-Pacific region, from Manual of the Living Conidae, by Rckel, Korn and Kohn (1995). They are reproduced with the kind permission of the present publisher, Conchbooks.

All plates and figures referred to in the text are also in Rckel, Korn & Kohn, 1995. Manual of the Living Conidae Vol. 1: Indo-Pacific Region.

The range maps have been modified so that each species account has it own map, rather than one map that showed the ranges of several species in the original work. This was necessary because each species account is on a separate page on the website and not confined to the order of accounts in the book.

 

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