Phyllochaetopterus Grube, 1863
Phyllochaetopterus sp. 1
Vouchers. VINSON WEST: station 1MFA and INFLEXIBLE: station 2MFA.
Note: The morphological description of chaetopterids is structured in 3 different body regions following Bhaud (1998): anterior (region A), mid-body (region B) and posterior (region C) (e.g. A4 = chaegier 4 in region A, B1= chaetiger 1 in region B) .
Diagnosis. Small sized species, all specimens incomplete, measuring 5mm long and 0.75-1mm wide for 20 chaetigers. Body regions with the following number of chaetigers: 9A, 2B and at least 9C (specimen incomplete) with C1-C4 inflated. Eyes absent. Chaetiger A1 with short dorsal, short, wide, “lobes”, far apart, situated lateral to the palps. Chaetiger A4 with about 6 stout modified spines in a single row, decreasing in size ventrally; each spine amber coloured; cup shaped (distally expanded), with several (about 8) teeth on both lateral edges. Region A also with lanceolate chaetae.
Glandular ventral shield as a white band on ventral side of A4. Region B with two chaetigers; B notopodia foliaceous, bilobed; B neuropodia each with single band of uncini. Region C with notopodia, elongated, slender, with two long slender, subdistally lanceolate protruding chaetae; C neuropodia bilobed, with uncini. Mid to posterior C region and pygidium missing. Tube not observed.
Remarks. Based on comparative table of the known Phyllochaetopterus species (see Nishi and Rouse, 2007), the Falkland Island specimens belong to group C: species with several (6 or more) spines in chaetiger A4, 9 chaetigers in region A and only 2 chaetigers in region B. Currently, there are four other species in this group, all from tropical regions: P. aciculigerus Crossland, 1904 from Maldives, P. herdmani (Hornell in Willey, 1905) from Sri Lanka, P. verrilli Treadwell, 1943 from Hawaii (P. verrilli is considered a synonym of P. brevitentaculata from Palmyra Atoll, Pacific Ocean). Given the differences in distribution, Falkland Island specimens likely represent a new species, but comparison with type material will be needed to confirm this. Falkland Island specimens also differ from the only known species from the region Phyllochaetopterus monroi Hartman, 1967 (type locality Strait of Magellan), which belongs to group A (Nishi and Rouse, 2007) as it possesses 9 chaetigers in region A, 2 chaetigers in region B, but only 1 large spine in chaetiger A4. Falkland Island specimens likely represent a new species, but better preserved material may be needed to fully diagnose this species, until such time it is assigned here to morphospecies Phyllochaetopterus sp. 1.
