Neothoa bilderbacki, Gordon, 2020

Gordon, Dennis P., 2020, New Hippothoidae (Bryozoa) from Australasia, Zootaxa 4750 (4), pp. 451-476 : 459-460

Neothoa bilderbacki n. sp.

( Figs 5B, C ; 6A, B )

Etymology. Honorific for Dr David Bilderback, Bandon, Oregon, who collected the pebble bearing the sole Neothoa specimen and recognised it as being of interest.

Material examined. Holotype: NIWA 132850 , on beach-cast pebble with other bryozoans, 43.5196° S, 172.7366° E, New Brighton , Christchurch, New Zealand, 8 April 2010, collected by D. Bilderback.

Description. Colony small, ramifying, uniserial, 3.10 mm maximum diameter. From proximal end of colony (concealed), short chains of 5–6 autozooids radiate outwards, budding autozooids at proximal end of each chain to establish branches, thereafter budding mostly female zooids. ZL 371±26, 322–405 (14); ZW 181±12, 163–203 (14).

Autozooids claviform, widest mid-length, tapering and shortly caudate proximally ( Fig. 5B ), budding a daughter autozooid mid-distally and 1–2 autozooids or 2 female zooids from midlateral pore-chambers. Frontal shield convex with weak median carina on distal third in some zooids, sloping proximad; shield smooth with weak transverse ridges and longitudinal striae. Orifice gently sloping downwards distad, longer than wide when viewed en face ( Fig. 6A ), with moderately deep, wide, rounded-V-shaped sinus delimited by small, rounded condyles. OL 72±6, 67–80 (4); OW 52±4, 47–56 (4).

No zooeciules or male zooids.

Female cystids typically borne in opposing pairs from runner parent autozooids, more or less triangular, with part or all of one side contiguous with parent zooid. Ovicell prominent, terminal, cleithral; ooecium formed from distal (ooecial) kenozooid, about as large as female cystid, roughly subglobular, with a scattering of 4–8 small pseudopores of varying size. Ooecial kenozooid with one distal or distolateral pore-chamber opening. Dimorphic combined maternal aperture much broader and shorter than autozooidal orifice ( Figs 5B, C ; 6B ), proximal margin gently concave, no separate sinus or condyles. ♀ ZL 294±27, 250–338 (13); ♀ ZW 149±24, 118–186 (13); OoL 152±18, 130–197 (13); OoW 158±18, 135–200 (13); ♀ OrL 70±3, 65–74 (13), ♀ OrW 76±5, 66–85 (13).

Ancestrula not seen (concealed by organismal overgrowth).

Remarks. Neothoa bilderbacki n. sp. is only the fourth species to be recognised in the genus and the first outside of southern South America. The type species, Neothoa patagonica ( Busk, 1852b) , from the Patagonian coasts of Chile and Argentina, has proportionally broader ooecia with only 1–2 pseudopores. Neothoa chiloensis ( Moyano, 1982) , also found on the coasts of Chile and Argentina, has proportionally smaller ovicellate zooids than in N. bil- derbacki and also fewer ovicellar pseudopores. Neothoa vivianii ( Moyano, 1986) is most like N. bilderbacki n. sp., having a similar number of ovicellar pseudopores (6–7), but autozooids are less clavate, the cauda being very short to non-existent. Hippothoa -like Miocene Neothoa reptans Pérez, López-Gappa & Griffin, 2015 from Argentina has longer autozooidal caudae than in any living species, including N. bilderbacki n. sp., and a carina of short umbones.

Distribution. Endemic; known only from a beach-cast pebble at New Brighton, Christchurch, New Zealand. Associated bryozoan species on the pebble include Celleporina sinuata , Exochella levinseni , Fovoporella spectabilis , Platonea sp., Schizosmittina sp. and Smittoidea maunganuiensis .

Figures

FIGURE 5. Plesiothoa gerroa n. sp., NIWA 122607 (paratype): A, ovicellate zooid showing lateral profile, with adjacent autozooids and zooeciules. Neothoa bilderbacki n. sp., holotype NIWA 132850: B, axial chain of autozooids with laterally budded ovicellate zooids; C, autozooid and laterally budded ovicellate zooid. Scalebars: A, B, 300 μm; C, 100 μm.

FIGURE 6. Neothoa bilderbacki n. sp., NIWA 132850 (holotype): A, B, en face views of autozooidal and ovicellate (dimorphic) orifices, respectively, tilted to show maximum lengths. Jessethoa ausubeli n. gen., n. sp., C–H (NIWA 132855), I, J (NIWA 132854, paratype): C, autozooids and zooeciules from proximal part of colony; D, elongate-oval ancestrula (middle zooid) with bipolar budding; E, oval ancestrula (at proximal end) with unipolar budding distalwards; F, close-up of ancestrula in E; G, another ancestrulate colony with bipolar budding (ancestrula lower middle); H, autozooids with frontal and laterally budded zooeciules; I, autozooidal orifice; J, zooids, mostly ovicellate, from crowded part of colony with frontal budding. Substratum darkened in D, E, H to show zooid outlines more clearly. Scalebars: A, B, 50 μm; C, D, 300 μm; E, J, 500 μm; F, 200 μm; H, 400 μm; I, 30 μm.