Neomediomastus Hartman, 1969
Neomediomastus sp. 1
Voucher. SEALION: station 1MFA.
Diagnosis. Voucher is a small, incomplete specimen, fragment about 4.5mm long and 0.4mm wide for 16 chaetigers; first 6 chaetigers with notochaetae only; from chaetiger 7 hooded hooks only. Body overall robust, cylindrical, of nearly uniform width, abdomen only slightly tapering; annulation distinct. Colour in alcohol tan.
Prostomium as a short, wide conical lobe. Peristomium simple, wide achaetigerous ring. Eyes absent. Everted proboscis, soft, inflated sac, densely covered by papillae.
Chaetigers 1-6 with notochaetae only in both rami; notochaetae capillaries, unilimbate with narrow wings, arranged in two rows of shorter and longer notochaetae. Abdomen from segment 12 (=chaetiger 11). Both rami with multidentate hooded hooks with relatively slender shaft, series of very small teeth (no main fang apparent), with truncated hood. The rest of abdomen unknown. Pygidium unknown.
Remarks. The combination of characters such as 6 chaetigers with notochaetae only (hooks only present from chaetiger 7) and 12 thoracic segments is consistent with genus Neomediomastus Hartman, 1969. Similar genus Barantolla Southern, 1921 has only 11 thoracic segments. Currently, only two species in the genus Neomediomastus are known: N glabrus (Hartman, 1960) described from Southern California and N. leptus Green, 2002 from Thailand. It is likely that Falkland Islands specimens represent a new species, but better preserved specimens will be necessary to fully diagnose this species. Care should be taken not to confuse these with Notomastus, which has a similar body shape and appearance, but has 11 chaetigers with notochaetae only.