Hoof Shells of the Hipponicidae Family
Five Hoof Shells of the Hipponicidae Family can be found in this website:
Phylogeny: Hoof Shells of the Hipponicidae Family are gastropod mollusks in the Littorinimorpha order. This order is large and very diverse in shape including snail-like, cowry shaped, and limpet-like. Most are marine species but some are found in freshwater or on land. They all have a twisted shell and a muscular foot that is used for movement. The key characteristic is that they all exhibit torsion, which is a process where the body twists so that the anus, gills, mantle cavity, and reproductive organs all point forward. There are sixteen superfamilies in this large order. Hipponicidae is the only family in the superfamily Hipponicoidea. There are no subfamilies in this family, but there are eight genera and about sixty-three species. Shells in the Hipponicidae Family are also commonly known as Horse Hoof Shells and Hipponicids.
Description: Hoof Shells are small to medium-sized, solidly constructed shells. They resemble limpet shells in that they have a flattened cone-shape but they are thicker than limpets. Their apex is located posteriorly, and it points posteriorly. The spiral is very small, and often difficult to notice. The exterior of these shells may be sculpted with commarginal lamellae, scales, or radiating ribs. They derive their family name from the horseshoe shaped muscle scar found on the shell’s interior. The horseshoe opens toward the anterior. Hoof Shells are generally white in color and many are covered with a brown, fibrous, periostracum. The largest species in this family reach 3.0 cm (1.2 inches) in length.
Habitat and Distribution: Hoof Shells are found are found in a variety of habitats in the intertidal zone and at depths up to 650 m (1,650 feet). Juvenile Hoof Shells are mobile and move around on hard substrate. As they mature, they attach themselves to rocks, or larger shells and become sedentary. They then secrete a calcareous base plate that functions like an operculum that looks like a second valve to the shell, leading some to misidentify the shell as a bivalve. They are found in tropical to temperate seas, worldwide. Six species from the Hipponicidae Family are found in Mexican waters.
Natural History: Hoof Shells feed primarily on organic fragments, of algae and detritus. Because they are sedentary, they use their extendable snout to reach food sources and are dependent on water movement to bring them food. Those attached to other shells benefit by getting carried to new food sources or by feeding of the wastes of their hosts. They are preyed upon by crabs, fish, and predatory mollusks. They are sequential hermaphrodites, beginning life as males and transitioning into females. They reproduce sexually, with either indirect fertilization or external fertilization through broadcast spawning.