Paracaudina ambigua O’Loughlin and Barmos, 2011

Paracaudina ambigua O’Loughlin and Barmos View in CoL sp. nov.

Figure 1a View Figure 1 , 2 View Figure 2

Material examined. Holotype. Western Australia, Shark Bay, FWA– WAM RV Naturaliste Shark Bay Survey II Feb / Mar 2003, stn 13/173/P, 24º47.02'S 113º21.97'E to 24º46.48'S 113º22.08'E, 24 m, 6 Mar 2003, S. Morrison and S. M. Slack-Smith, WAM Z29767 About WAM . GoogleMaps

Paratype. Western Australia, Ningaloo Marine Park , AIMS RV Solander, stn RVS 4545–D069, 23º48'S 113º30'E, 33 m, 1 Feb 2008, M. Salotti and S. M. Slack-Smith, WAM Z23331 About WAM GoogleMaps (1).

Diagnosis. Paracaudina species up to 45 mm long ( holotype, caudal taper but anal end and valves missing), body up to 15 mm high (body flattened laterally); body wall thick, soft to semi-gelatinous, white (preserved); posterior body with caudal taper to short discrete tail (evident in paratype); ossicles different mid-body and caudally; mid-body ossicles predominantly small irregular rods, frequently forming a single loop, or small plates with up to 4 perforations, these ossicles up to 40 µm long; rare mid-body irregularly oval perforated plates with spinous margin and some secondary bridging, about 64 µm long; caudal ossicles irregularly oval to round to octagonal perforated plates, long pointed spinous margin, surface spines and bridges and secondary development, some plates chilensis -like with box and cross bridges over central perforation, caudal ossicles typically 56–64 µm long.

Type locality. Central Western Australia, Shark Bay .

Distribution. Central Western Australia, Shark Bay, Ningaloo Marine Park; 24– 33 m.

Etymology. From the Latin ambiguus (of double meaning, uncertain), feminine ambigua , referring to the generic uncertainty created by the presence of Acaudina -like ossicles mid-body and Paracaudina -like ossicles posteriorly.

Remarks. Paracaudina ambigua O’Loughlin and Barmos sp. nov. is distinguished diagnostically amongst Paracaudina species by having fine irregular rod and loop ossicles in the mid-body wall and marginally spinous chilensis -like plate ossicles in the caudal region, some with the characteristic cross and box bridges over a central perforation. Both specimens are in poor condition, but the ossicles are in excellent condition and characterise the new species. Distal pairs of digits are evident on a few tentacles of the holotype, but the condition of the tentacles is such that a second pair is not clearly evident on any tentacle. The caudal part is missing from the holotype, but a distinct narrow tail and soft anal valves are present on the paratype ( 18 mm long).