Filicisparsa albobrunnea, Gordon & Taylor, 2010

Gordon, Dennis P. & Taylor, Paul D., 2010, New seamount- and ridge-associated cyclostome Bryozoa from New Zealand, Zootaxa 2533 (1), pp. 43-68 : 46

Filicisparsa albobrunnea n. sp.

( Fig. 2 A–E )

Material examined. Holotype: NIWA 61240 , from TAN0104 cruise, Stn 3, 42°45.48– 42°45.18’S, 179°59.47– 179°59.54’ W, “Graveyard” Seamount, Chatham Rise, 943–1097 m depth, collected 15 April 2001 . Paratypes: NIWA 61241 , same locality as holotype . Other material: TAN0104 Stns 1, 43, 80, 82, 149, 150, 194, 336, 389, 399.

Distribution. “Graveyard Seamount Complex”, north-central Chatham Rise, New Zealand, 750–1181 m.

Etymology. Latin albus, white, and brunneus, brown, alluding to the tan coloration of the ephebic parts of colonies contrasting with the white distal branches.

Description. Colony initially encrusting, ramifying, forming biserial lobes by branching laterally on the substratum from the primary branch that originates from the ancestrula, which has not been seen. Once the basal parts of a colony are established, an erect biserial branch is formed, accompanied by the development of robust kenozooidal calcification at its base, 0.92–0.93 mm in diameter.

Branching dichotomous. Erect branches attaining 10–15 mm in height, straight or curving, angled at c. 45 degrees to the substratum, subtriangular in cross section near the base of the branch, becoming subcircular to circular in cross section in distal parts; diameter of erect branches distal to first bifurcation 0.49–0.62 mm. Zooidal peristomes 0.14–0.15 mm diameter, borne only on the frontal sides of branches, arranged in pairs that are deflected alternately to left and right of the branch axis, the frontalmost peristome of each pair longer than the one beneath it, their openings facing abfrontally. Gonozooids sporadic, occurring frontally at branch dichotomies, brood chamber subglobular, 0.99–1.17 mm in diameter, densely pseudoporous, the ooeciostome simple, 0.16 mm in diameter, opening mid-distally, the ooeciopore circular.

Remarks. Colonies are distinctive and easily recognised, not only because of their general size and morphology but because of the tan coloration of older parts of branches in many instances, whereas distal parts are always white.

The generic attribution of this species is problematic. Two Recent genera can be ruled out, Exidmonea because of its more complex gonozooids, and Tervia because the gonozooids of this genus are on the dorsal sides of the branches. The type species of Filicisparsa is from the Late Cretaceous (Santonian to Upper Maastrichtian) of western Europe. Its erect branches have laterally alternating pinnules — short lateral projections comprising a small cluster of 4–5 zooidal peristomes — and sparse apertures on the frontal sides of the branch, which is not the case in the new species. Brood chambers are somewhat globular and borne frontally on branches. The species from the Chatham Rise resembles F. sommerae in overall colonial morphology, i.e. having erect, dichotomously branching colonies with zooids on one side only, no dorsal kenozooids, and a similar frontally borne brood chamber. The ‘pinnules’ in our material comprise only a pair of peristomes, not a cluster, and there are no frontal apertures; furthermore, the frontally borne brood chambers are located at branch bifurcations. To create yet another new monotypic genus of Cyclostomata would highlight the apparent differences between the Late Cretaceous species and our Recent material but would not otherwise advance our understanding of their actual relationships. Accordingly, we provisionally use Filicisparsa for the Recent specimens from the Chatham Rise.

Figures

FIGURE 2. Filicisparsa albobrunnea n. sp. (TAN0104 Stn 3). A, reflexed branch showing disposition of peristomes; B, brood chamber at branch bifurcation (holotype); C, D, parts of ephebic branches showing reparative calcification; E, abfrontal side of a brood chamber.