Phylogeny: Cup-and-Saucer Shells and Slipper Shells of the Calyptraeidae Family are gastropods 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. The Calytraeidae Family is the only family in the superfamily Calyptraeoidea. The Calyptraeidae Family contains eleven genera – Bostrycapulus with ten species, Calyptraea with twenty-one species, Crepidula with forty-nine species, Crepipatella with nine species,  Crucibulum with nineteen species, Desmaulus with three species, Ergaea with one species, Grandicrepidula with two species,  Maoricrypta with six species, Sigapatella with seven species, and  Trochita with five species. Shells in this family are also commonly known as Slipper Snail Shells, Chinese Hat Shells, and Calyptraeids.

Description: Both Cup-and-Saucer Shells and Slipper Shells are thin and small to medium-sized. Their shells may be circular, elliptical or oval in outline. Often their outline is shaped by the substrate they are attached to. They have a very flattened conical profile. The spire may be small or absent. The apex may be centered or near the margin. These shells are coiled but the coiling is not always easy to recognize. The exterior sculpting may consist of wavy ridges, or fine bumps or small spines, which may be radiating or spiraling. The interior of the shell is smooth. The columella is modified into an interior shelf (septum), which provides support for the animal’s soft parts. In Cup-and-Saucer Shells this shelf is curved into a full or partial cup shape. The cup’s attachment points will vary between species. In Slipper Shells a flat shelf covers around half of the interior. Shells in this family tend to be in various shades of white, gray, or brown. The largest shells in this family is 5.6 cm (2.2 inches) in length.

Habitat and Distribution: Cup-and-Saucers and Slipper Shells are found on hard surfaces such a rocks, stones, and often times, on other sea shells. They live intertidally, and at depths up to 200 m (655 feet). They are generally sedentary which allows their base to conform to the shape of the surface on which they reside. They are found worldwide in tropical, to polar seas. Twenty species from the Calyptraeidae Family are found in Mexican waters.

Natural History: Calyptraeids are suspension feeders, which use mucous strands to capture plankton and detritus from the water column. In turn they are preyed upon by crabs, predatory mollusks and sea stars. All individuals in the Calyptraeidae Family start life as males and transition into females later in life. Some species form “mating stacks”, where multiple males stack on top of one female. When the female dies, the bottom male becomes a female.