Lithopoma
A genus of turban snails with a calcareous operculum.
Lithopoma is a genus of marine gastropod mollusks, specifically medium-sized to large sea snails that belong to the turban snail family, Turbinidae, and its subfamily Turbininae. These snails have a calcareous operculum. Their shells are elevated and imperforate, with a turbinate or trochiform shape and a plicate spire that is flat or concave underneath. The shell’s periphery is either carinated or rounded, and the base is somewhat convex. The upper whorls have radial plications. The operculum is oval, coarsely granulose on the outside, and either simply convex or marked with a curved spiral rib whose ends are connected by a straight one; its nucleus is submarginal. This genus is found in the Caribbean Sea, the Gulf of Mexico, and off the Lesser Antilles. Species now placed in Lithopoma were formerly assigned to the genus Astraea. Recognized species include Lithopoma americanum, Lithopoma brevispina, Lithopoma caelatum, Lithopoma phoebium, Lithopoma tectum, and Lithopoma tuber. Several names have been synonymized, such as Lithopoma gibberosa and Lithopoma gibberosum with Pomaulax gibberosus; Lithopoma heliotropium with Astraea heliotropium; Lithopoma imbricatum with Lithopoma tectum; Lithopoma phoebium longispina with Lithopoma phoebium; Lithopoma tectum americanum with Lithopoma americanum; Lithopoma tuber venezuelensis with Lithopoma tuber; and Lithopoma undosum with Megastraea undosa.
Quick Facts
- Taxon
- Lithopoma
- Type Species
- Trochus tuber
- Type Species Authority
- Linnaeus, 1758
Facts from the source article.
Lore & Background
The elevated, imperforate shell of Lithopoma has a turbinate or trochiform shape, with a plicate spire that is flat or concave below. Its periphery is carinated or rounded, and the base of the shell is somewhat convex. The whorls above are radiately plicate. The operculum is oval, outside coarsely granulose, and either simply convex or with a curved spiral rib with its terminations connected by a straight one; the nucleus is submarginal.
This genus occurs in the Caribbean Sea, the Gulf of Mexico and off the Lesser Antilles. Species within this genus were previously placed in the genus Astraea. Several species have been brought into synonymy, including Lithopoma gibberosa and Lithopoma heliotropium, which are now considered synonyms of other genera such as Pomaulax and Astraea.
Reader's Guide
Lithopoma represents a group of marine snails within the Turbinidae family, notable for their calcareous operculum and historical placement in the genus Astraea. The genus is distributed in the Caribbean Sea, Gulf of Mexico, and off the Lesser Antilles, indicating a restricted tropical Western Atlantic range. Its shell morphology—turbinate or trochiform, imperforate, with a plicate spire and carinated or rounded periphery—distinguishes it from related genera. The operculum's coarse granulation and spiral rib structure are key diagnostic features. The synonymy list shows taxonomic revisions, with some species reassigned to Pomaulax, Megastraea, or retained in Astraea, reflecting ongoing refinement of turbinid classification. The genus includes six accepted species, such as Lithopoma americanum and Lithopoma tuber, which were originally described under other names. This entry draws solely on the provided source article.
Did You Know?
- The shell of Lithopoma is imperforate and has a turbinate or trochiform shape.
- The operculum is calcareous, oval, and coarsely granulose on the outside.
Frequently Asked Questions
Who is Lithopoma?
Lithopoma is a genus of medium-to-large sea snails placed in the turban snail family Turbinidae, subfamily Turbininae. Before its current name was adopted, these snails were lumped together under the older genus Astraea.
What does a Lithopoma shell actually look like?
The shell is elevated, imperforate, and takes a turbinate or trochiform (cone-like) profile with a spire that shows radial plications and sits flat or slightly concave on its underside. The periphery may be either carinated or rounded, and the base curves outward in a somewhat convex manner.
Where do you find Lithopoma in the wild?
These snails are a regional group, occurring in Caribbean Sea waters, throughout the Gulf of Mexico, and along the coasts off the Lesser Antilles. They are not a globally distributed genus.
What's the deal with Lithopoma's operculum?
The operculum is a calcareous (calcium-carbonate) plate that is oval in outline and coarsely granulose on its outer face. Internally it is either simply convex or carries a curved spiral ridge.
Why do fans and taxonomists treat Lithopoma as its own genus rather than just another Astraea?
The plicate spire, the specific combination of an elevated imperforate shell with a carinated-or-rounded periphery, and the distinctive operculum morphology set it apart enough for taxonomists to split it from Astraea. It now stands as a separate genus within Turbininae with its own diagnostic shell architecture.
More in Marine Snails, Part 2 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced