Ceratocephale Malmgren, 1867
Ceratocephale sp. 1
Voucher. SEA LION: station 38MFA.
Diagnosis. Voucher specimen posteriorly incomplete 7.0 mm long and 1.5 mm wide (including parapodia), for 25 chaetigers (damaged). Alcohol preserved material pale yellow with golden setae and black aciculae. Prostomium rectangular (slightly wider than long), with pair of long, thin, triangular antennae lying closely against palps. Palps tapering, about the same length as antennae, with large palpophores. Eyes absent. Two pairs of tentacular cirri of similar length, all rather short. Pharynx inverted (not observed).
Parapodia bi-ramous, with notopodia slightly shorter than neuropodia. Dorsal cirrus slender tapering, only slightly longer than notopodial ligule, their cirrophores appear expanded on most chaetigers. Notopodia with elongate prechaetal ligule and short, blunt postchaetal lobe. Neuropodia (mid body) with bluntly rounded postchaetal lobe and elongate digitiform precheatal ligule. Ventral neuropodial ligule digitiform, elongated. Ventral cirri not branched on chaetigers 1-2, from chaetiger 3 bifid till end of the fragment, ventralmost cirrus tiny on chaetiger 3 (easily overlooked), about ½ the length of primary cirrus in chaetigers 4-5, only slightly subequal in length to primary cirri on subsequent segments.Notopodial chaetae arranged in 2 bundles on either side of prechaetal ligule. Neuropodial chaetae similarly arranged. Chaetae consist entirely of homogomph spinigers with finely serrated blades; chaetae straw coloured. Narrow transverse dorsal ridges connecting the notopodia present from chaetiger 5 till end of the fragment. The rest of the body and pygidium uknown.
Remarks. Genus Ceratocephale is characterised by bifid ventral cirri (this characters is also shared with genus Gymnonereis, which additionally also has bifid dorsal cirri). The appearance of the double ventral cirrus together with characters such as – presence or absence of eyes, appearance of expanded dorsal cirriophores, presence of dorsal ridges, form of chaetae and characters derived from proboscis. The differences appear to be rather subtle (see Table 1. for comparison). Falkland Island specimens agree most with C. hartmanae having bifid ventral cirri from chaetiger 3 and all chaetae homogomph spinigers, but this species is unique in having mid-dorsal flaps in median body region. While the presence of such flaps cannot be assessed in Falkland Islands material (all specimens very short) two species differ in chaetiger in which dorsal ridges start. Currently we prefer to assign Falkland Island specimens to morphospecies Ceratocephale sp. 2.
