The common name of this fish is derived from the
lower lobe of its pectoral fins, which are extremely long and thread-like. While
most snailfish have an adhesive disc, which is comprised of the pelvic fins, the
threadfin seasnail does not have this feature. The rest of its body features are
typical of snailfish, such as a tapering body, dorsal and anal fins that run the
length of the body, a large head and mouth, and fan-like upper pectoral fins.
Its body is a bright pink to red colour and grows no larger than 31 cm.
Threadfin seasnails occur in the northern Atlantic
and off Baffin Island. This species prefers deep water, usually between 1150 and
2341 m, with muddy bottoms. Little is known about their biology, but ripe females
have been caught throughout the summer and into December. They carry 70 or more
eggs that are 7 mm in diameter.