On July 14, 1997, in the Gulf of Mexico, a dense population of polychaete worms dwelling in methane hydrates associated with cold seeps was discovered and sampled at 538 meters depth. The worms belong to the family Hesionidae and represent a new species of the genus
Hesiocaeca. They differ from the two previously described species by the shape of the prostomium, the shape of the setae and the presence of anal cirri.