Frontohornera frontalis, Grischenko & Gordon & Melnik, 2018

Grischenko, Andrei V., Gordon, Dennis P. & Melnik, Viacheslav P., 2018, Bryozoa (Cyclostomata and Ctenostomata) from polymetallic nodules in the Russian exploration area, Clarion - Clipperton Fracture Zone, eastern Pacific Ocean-taxon novelty and implications of mining, Zootaxa 4484 (1), pp. 1-91 : 29-32

Frontohornera frontalis n. sp.

( Figs 2J, K , 16–18 )

Material examined. Holotype: ZIRAS 1/50707, colony detached from nodule, YMG R.V. Yuzhmorgeologiya

cruise YMG4–13, Stn 292, 27 July 2014, 13.03353° N, 132.49292° W, 4829 m. Paratype: ZIRAS 2/50708, colony attached to nodule particle, YMG R.V. Gelendzhik cruise GLD4–11, Stn 210, 20 April 2012, 13.35817° N, 133.27183° W, 4815 m. Additional material: YMG4–07, Stn 124; GLD4–11, Stn 215; YMG4–14, Stns 329, 334. Total specimens examined six.

Etymology. Latin, frontalis , frontal, alluding to the frontally borne gonozooid.

Description. Colony erect, white, to 2.81 mm high, 6.76 mm broad, dichotomously branching once in a single plane ( Fig. 16A, B ), or with short additional bifurcation to produce a third, short branch near colony center ( Fig. 18G, H ). Stem diameter 0.32 × 0.37 mm, widening to colony base (0.66–0.76 mm). With distinct frontal and abfrontal faces ( Fig. 16 ), entire surface interior-walled, textured irregularly with minute dimples, granules, ridges and furrows ( Fig. 17A–G ), with longitudinal linearities only on stem of colony; conspicuous ribbing (nervi) and grooves (sulci) lacking. Pores simple, tiny, sparse.

Autozooids in 2–4 series, their peristomes produced frontally upwards, relatively short along frontolateral and central parts of branch, longest along abfrontolateral margin, with simple circular apertures, no apertural spines ( Fig. 17A–F, I ). Peristomes somewhat dimorphic ( Fig. 17F ), short and uniformly tubular with circular apertures in central face of branches, but strongly elongated, with aperture having shape of teardrop, isosceles triangle or irregular oval along branch margins. Peristome wall interiors with short, thin spinules proximal to aperture ( Fig. 17I ). Cancelli most numerous on central part of branch distal to gonozooid ( Figs 16A , 17A, E, J ), otherwise sparse, shallow, of varying size. Abfrontal face of colony with outlines of autozooidal tubes ( Figs 16B , 17G ), their longitudinal contours converging proximad.

Gonozooid frontally borne, adjacent to second dichotomy ( Fig. 16A ), subglobular, surface like that of colony but with slightly denser prickled granules ( Fig. 17H, J, K ), frontal peak and distal sides of chamber converging towards short ooeciostome that curves frontalwards ( Fig.17H, J, K ), ooeciopore transversely oval ( Fig. 17L ).

Ancestrular zooid not seen in isolation; earliest growth stages encountered show lowest peristome of colony (presumed ancestrular peristome), which appears to be wholly erect, though concealed within basal skirt of extrazooidal calcification ( Fig. 18G, I ). Peristome of daughter zooid above it in series, but in another colony ancestrular and two daughter peristomes occur as cluster of three ( Fig. 18B ).

Measurements (mm). Holotype, ZIRAS 1/50707 ( Fig. 16A, B ): ZL 0.569–0.763 (0.663 ± 0.071). Branch center: PeL 0.072–0.197 (0.122 ± 0.042); PeD 0.141–0.162 (0.153 ± 0.008); ApD 0.129–0.141 (0.137 ± 0.004). Branch margin: PeL 0.194–0.526 (0.374 ± 0.102); PeD 0.110–0.146 (0.135 ± 0.011); ApL 0.132–0.176 (0.156 ± 0.016) (n = 7); ApW 0.122–0.147 (0.132 ± 0.008) (n = 7). Gonozooid (n = 1): GZL 0.744; GZW 0.511; GZH = 0.377; OsL 0.167; OsW 0.132; OsH 0.196; OpL 0.073; OpW 0.071.

Non-type specimen GLD4–11, Stn 210 ( Fig. 18G–I ): AnPeD 0.144 (n = 1).

Remarks. Frontohornera frontalis n. sp. is represented in the collection by six colonies of varying ages and sizes. Only one reproductively mature colony was encountered. All were found attached to polymetallic nodules.

Distribution. Recorded from six stations within coordinates 13.03353– 14.29353° N, 131.87598– 134.23457° W, at depth range 4815–5166 m.

Figures

FIGURE 2. Colonies of some cyclostome bryozoans, in vivo, attached to polymetallic nodules. A–E, Pandanipora helix n. gen., n. sp.: A, specimen GLD4–09, Stn 190; B, specimen GLD4–12, Stn 262; C, specimen YMG4–07, Stn 143; D, specimen YMG4–13, Stn 295; E, specimen GLD 4–11, Stn 212. F, Tubuliporina sp. indet., specimen YMG18–01, Stn 7. G, H, Abyssoecia elevata n. gen., n. sp.: G, specimen GLD4–09, Stn 196; H, specimen GLD4–09, Stn 191. I, Discantenna metallica n. sp.: specimen GLD4–11, Stn 224. J, K, Frontohornera frontalis n. gen., n. sp.: J, specimen YMG4–07, Stn 124; K, specimen GLD4–11, Stn 210. L, Alyonushka hystricosa n. gen., n. sp.: specimen GLD4–09, Stn 199. M, Calyssopora volcano n. gen., n. sp.: specimen YMG18–01, Stn 33. N, O, Anyuta anastema n. gen., n. sp.: N, specimen GLD4–09, Stn 180; O, specimen YMG4–06, Stn 71. Scale bars: 1 mm.

FIGURE 16. Frontohornera frontalis n. gen., n. sp. Holotype specimen, ZIRAS 1/50707, respectively seen in A, frontal and B, abfrontal views. Scale bars: 1 mm.

FIGURE 17. Frontohornera frontalis n. gen., n. sp. Holotype, ZIRAS 1/50707, showing details of morphology. A, part of branch distal to gonozooid, showing cancelli and zooidal peristomes; B, part of infertile branch with fewer cancelli; C, D, parts of infertile branch showing peristomial dimorphism; E, part of branch near gonozooid showing numerous cancelli and peristomial dimorphism; F, zooids showing peristomial and apertural dimorphism; G, abfrontal part of branch in vicinity of gonozooid; H, J, K, gonozooid profiles; I, autozooidal peristome showing interior spinules; L, ooeciostome and ooeciopore. Scale bars: A, B, D, E, G, 300 µm; C, H, J, K, 200 µm; F, 150 µm; I, 100 µm; L, 50 µm.

FIGURE 18. Frontohornera frontalis n. gen., n. sp. Progressive stages of development of young colonies. A–C, specimen GLD4–11, Stn 215, from different angles; D–F, specimen YMG4–14, Stn 334, from different angles; G–I, specimen GLD4–11, Stn 210, in frontal and abfrontal views and a close-up of the colony base with secondary calcification. Scale bars: A–H, 500 µm; I, 250 µm.