Erinaceusyllis is a genus belonging to the phylum Annelida, a group known as the segmented worms. Erinaceusyllis is a marine genus, while some of its species are possibly cosmopolitan. Its type species is Erinaceusyllis erinaceus, formerly Sphaerosyllis erinaceus (Claparède, 1863). As of 2015, at least 12 species have been described, namely E. belizensis, E. bidentata, E centroamericana, E. cirripapillata, E. cryptica, E. erinaceus, E ettiennei, E. hartmannschroederae, E horrocksensis, E. kathrynae, E. opisthodentata, E. serratosetosa. The family contains two other genera, Sphaerosyllis (48 species) and Prosphaerosyllis.