Reptadeonella violacea is an encrusting bryozoan, found in warm temperate waters. Colonies form broad, often extensive, encrustations which are deep purple when living with a paler periphery of developing autozooids. Autozooids are hexagonal, pear-shaped or lozenge shape. They are flat or slightly concave with a more or less marked central depression. Autozooid size is typically 0.5-0.68 by 0.2-0.34 mm.
Reptadeonella violacea is a warm temperate species that reaches its northern limit at the Isle of Man. In the British Isles it has a south-western distribution. It is present in the western English Channel and around the Channel Islands, but is absent from the North Sea. Outside of the British Isles, the species is widespread in the Mediterranean and has been reported from the Cape Verde Islands, West Africa, the Gulf of Mexico, the Caribbean, Brazil and the Pacific coasts of Mexico and North America
The species is able to colonise hard substrates in offshore waters, and may be abundant on shell banks.