Gephyrocapsa is a genus of haptophytes.
Haptophytes are a phylum of algae, sometimes called the Prymnesiophyta. All or most of them are single-celled photosynthetic phytoplankton.
The cells typically have two slightly unequal flagella and a unique organelle called a haptonema. This is superficially similar to a flagellum, but differs in its arrangement of microtubules, and in its use. The name comes from the Greek hapsis = touch, and nema = thread.