Facelinidae

Facelinidae is a family of aeolid nudibranchs, a group of small, marine gastropod mollusks commonly known as sea slugs. Members are typically slender and elongated, with numerous cerata (finger-like dorsal appendages) arranged along the dorsum. They possess paired oral tentacles and prominent rhinophores, and their coloration is often vivid, which may serve as warning or camouflage among their prey.

Ecology and biology: Facelinids are carnivorous, feeding primarily on hydroids and other small cnidarians, though some species take bryozoans or tunicates. As they consume cnidarians, they can incorporate nematocysts from their prey into cnidosacs at the tips of the cerata, which provides a chemical defense against predators. Reproduction is hermaphroditic; individuals typically mate in reciprocal fashion and lay gelatinous egg masses that hatch into free-swimming larvae.

Taxonomy and distribution: The Facelinidae are distributed worldwide, from temperate to tropical seas, inhabiting shallow coastal habitats such as rocky shores, kelp forests, and coral reefs. The composition of the family has been revised with advances in molecular systematics, and several genera previously placed in Facelinidae have been reassigned to other families within the superfamily Fionoidea. A well-known example genus within the broader group is Facelina, among others.