The larva of Ergentrema mugilis Paperna, 1964 (Ancyrocephalidae) occurring in Liza ramada (Risso, 1826) is described for the first time including the primary haptor description as well as the chaetotaxy. In addition, the sensillae position, previously unknown in the larva of Dactylogyrus extensus Muëller and Van Cleave, 1932 (Dactylogyridae) a parasite of Cyprinus carpio L., is specified. The comparison between these two chaetotaxies shows a proximity which was not obvious through the adult and larval haptor structure. The respective value of both criteria for the Monopisthocotylea phylogeny is discussed.