Common Name: Lasaeids or kelly clams
Key morphological features: The Lasaeidae are tiny, up to 30 mm in size. The thin, fragile shell is equivalve, with a round or elongated oval shape, and does not gape. The shell is composed of aragonite and exterior sculpture is smooth, with rare radial riblets or commarginal lines. Valve interiors are non-nacreous and the pallial line is uninterrupted. The interior shell margins are smooth. Species of Lasaeidae are isomyarian (both adductor muscles are equal in size) or slightly heteromyarian (one adductor larger than the other). The heterodont hinge is usually indented in an inverted V-shape, and contains parallel lateral teeth. Source: Mikkelsen, P.M., and Bieler, R. 2008. Seashells of Southern Florida: Bivalves. Princeton, New Jersey: Princeton University Press. 503 pp.
Geological range: Cretaceous to Recent (Mikkelsen & Bieler, 2008).
Diversity: There are 396 recognized living species of Lasaeidae and 79 genera (WoRMS database, unvetted). The Paleobiology Database recognizes 9 fossil genera and 38 fossil species of Lasaeidae (unvetted).
Paleoecology: The Lasaeidae are marine suspension feeders. They live freely on protected environments such as rock crevices, barnacles, and kelp holdfasts, or they may byssally attach to infaunal or epifaunal invertebrates such as crustaceans, sea urchins, or chitons. When attached to other organisms, Lasaeids feed on the mucous secretions or food particles generated by their hosts. Many Lasaeids can actively crawl using their foot. They can be found in oceans worldwide. Source: Mikkelsen and Bieler (2008).
Phylogenetic status: Polyphyletic. Molecular phylogenetic analyses by Goto et al. (2012) do not support the monophyly of Family Lasaeidae.