ARTOTROGIDAE Brady, 1880

Johnsson, Rodrigo & Neves, Elizabeth G., 2005, A revision of Metapontius (Siphonostomatoida: Artotrogidae) with the description of a new species associated with an octocoral from Eniwetok Atoll, Marshall Islands (USA), Zootaxa 1035, pp. 51-59 : 52

ARTOTROGIDAE Brady, 1880

Within the Artotrogidae there are presently 21 genera ( Boxshall & Halsey 2004), which can be grouped according to characters related to the fourth leg. Among the variable states, it is possible to observe the reduction of the leg to a protopod bearing 1 or 2 setae, as seen in Pseudotrogus (Johnsson & Rocha 2002) . Other conditions found are: the total absence of the endopod, as observed in Pteropontius , Cryptopontius , Dyspontius , Pulicitrogus and Ascidiopontius; or the absence of the whole leg, as in Artotrogus, Glyptotrogus, Tardotrogus and Sewellopontius . An uncommon, intermediary state is the endopodal ramus bearing two segments, found only in Arctopontius and Metapontius . All remaining genera of the family have P4 unmodified, with both rami present, and 3­segmented.Therefore Artopontius and Metapontius , among all other Artotrogidae genera, are probably very closely related. However, it is possible to distinguish these two genera based on the following characteristics. In Arctopontius , the pedigerous somite 4 is projected backwards as in the previous segment, reaching the mid­region of the genital double­somite. In Metapontius , pedigerous somite 4 is slightly rounded posteriorly, hardly reaching the lateral margin of the following pedigerous somite. Both genera also differ in the proportions of both lobes of the maxillule. In Arctopontius , the inner lobe is twice as long as the outer lobe while in Metapontius , the outer lobe is almost as long as the inner one.