Chrysostoma paradoxum
A marine snail with a thick, orange-mouthed shell from the Indo-Pacific.
Chrysostoma paradoxum, called the orange-mouthed top shell, is a marine snail in the Trochidae family. Its thick, strong shell is globular and porcelaneous, with a smooth surface that shows only faint growth lines. The upper whorls have very fine, dense spiral striations. The shell is whitish overall, covered in a close red or pinkish reticulation and mottling, sometimes with a few larger darker spots on top. The spire is very short, and the sutures are linear, bordered by a slight concavity or margination. There are six convex whorls, the last one globular. The aperture is half-moon shaped and reddish or golden-orange inside. The parietal wall has a very thick orange (rarely crimson) callus that projects as a short tongue-shaped lobe above the slight, often closed, umbilical perforation. The shell is imperforate or nearly so. Length ranges from 18 mm to 21 mm. This species lives on corals in the intertidal zone of the East China Sea, and off the Philippines, Japan, New Caledonia, Papua New Guinea, and Queensland, Australia.
Quick Facts
- Taxon
- Chrysostoma paradoxum
Facts from the source article.
Lore & Background
The shell of Chrysostoma paradoxum is globular, imperforate or nearly so, thick and strong, with a porcelaneous texture. Its surface is smooth, with scarcely visible lines of growth, while the upper whorls are microscopically and densely spirally striated. The color is whitish, closely reticulated and mottled all over with red or pinkish, often with a few larger dark maculations above. The spire is very short, and the sutures are linear, bordered by a slight concavity of the whorl or margination. The six whorls are convex, the last globular. The aperture is half-moon shaped and has a reddish or golden-orange color within. The parietal wall is covered with a very thick orange-colored (rarely crimson) callus, which projects in a short tongue-shaped lobe above the slight, often closed, umbilical perforation.
Reader's Guide
This species is documented from corals in the intertidal zone of the East China Sea, off the Philippines, Japan, New Caledonia, Papua New Guinea, and Queensland, Australia. Its description, provided by Crosse in 1866 and later referenced by Troschel, Watson, Schepman, and others, emphasizes the shell's porcelaneous texture and distinctive orange interior. The species is part of the Trochidae family, and its common name reflects the striking color of the aperture. The article notes that the callus is very thick and orange-colored, rarely crimson, and that the umbilical perforation is slight and often closed. The shell length ranges from 18 mm to 21 mm. The species has been included in works by Allan, MacNeil, Rippingale & McMichael, Habe, Hinton, Coleman, and Wilson, indicating its recognition in regional shell guides and scientific literature.
Frequently Asked Questions
What is Chrysostoma paradoxum?
Chrysostoma paradoxum is a small marine snail belonging to the Trochidae family, commonly known as the orange-mouthed top shell. It is a species native to Indo-Pacific waters, recognized for its compact, thick-walled shell.
What does the orange-mouthed top shell look like?
The shell is a globular, porcelaneous form that is whitish overall, overlaid with a tight network of red or pinkish reticulation and mottling, occasionally punctuated by a few larger dark spots. The aperture has a distinctive orange coloration, which gives the species its common name.
How big does Chrysostoma paradoxum grow?
Adult specimens measure between 18 and 21 millimetres in length, making it a relatively small top shell. Its six convex whorls are tightly coiled, with the final whorl being the most globular.
What makes Chrysostoma paradoxum's shell structure unique?
The shell has a very short spire with linear sutures bordered by a subtle concavity, and the upper whorls carry extremely fine, dense spiral striations. The surface is otherwise smooth, showing only faint growth lines, while the thick, strong walls give it a notably robust feel for its size.
Where can you find Chrysostoma paradoxum in the wild?
This species is native to the Indo-Pacific region, where it inhabits coastal marine environments. Like other members of the Trochidae family, it is typically encountered in shallow-water settings along that broad tropical and subtropical range.
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