Taxonomic notes on some Cheilostomata (Bryozoa) from Madeira
Author
Berning, Björn
text
Zootaxa
2012
3236
36
54
journal article
45230
10.5281/zenodo.211022
fc7d5cb4-2741-48de-b2c9-940d17bd6bab
1175-5326
211022
Phaeostachys schmitzi
(
Norman, 1909
)
n. comb.
(
Figs 19–22
,
Table 4
)
Schizoporella schmitzi
Norman, 1909
: 304
, pl. 41, fig. 2.
Material examined.
Holotype
:
NHMUK
1911.10.1.1109, by monotypy, Norman collection, Madeira, encrusting a
Glycymeris
shell (no further information provided as to exact location or depth).
Description.
Colony encrusting, unilaminar, multiserial. Zooids oval to hexagonal, broadest at about mid-distance, separated by shallow grooves. Frontal shield slightly convex, surface finely granular, irregularly perforated by up to 30 round pseudopores that decrease in diameter during ontogeny; occasionally with a low blunt conical umbo proximal to the sinus. Primary orifice about as long as wide, anter comprising about three-quarters of a full circle, delimited from a deeply U-shaped poster by straight horizontal or slightly sloping proximal margins, condyles fairly indistinct, broadest at proximolateral corners and thinning towards edges of the sinus; generally with 6– 7 seven spines around the lateral and distal orificial margin, rarely with 5 or even 4.
Ovicells not observed.
Avicularia adventitious, single or occasionally double, rarely absent, situated in lateral zooecial corner and/or directly suboral, directed proximally or distolaterally; rostrum elongated triangular, crossbar complete, no ligula, proximal uncalcified area semicircular, distal area subcircular.
Ancestrula tatiform, c. 420 x 310 µm, gymnocyst well-developed proximally, opesia comprising about twothirds of total length, surrounded by 10 spines.
TABLE 4.
Measurements (in µm) of
Phaeostachys schmitzi
n. comb.
ZL ZW OL OW AL AW mean 602 418 169 174 142 78 SD 55
44 8 12
16 8 min. 512 353 156 158 112 67 max. 725 512 182 197 173 93
n 20 20 20
20 13 13
Remarks.
Phaeostachys schmitzi
is remarkably similar to the
type
and only other known species in the genus
Phaeostachys
,
P
.
spinifera
(
Johnston, 1847
)
, which differs only in having a thinner avicularian rostrum and an ancestrula with 12 spines (
Hayward & Ryland 1999: 238
). In the absence of ovicells in the
type
specimen, and owing to the lack of additional colonies for comparison, it is difficult to judge whether these differences represent intra- or interspecific variation, and it could well be that the two forms will have to be synonymised in a future study. In any case, the similarity is remarkable, given that
P. spinifera
is a cool-temperate species, ranging from Brittany to the
Faroe Islands
, not documented from warmer regions further south (
Hayward & Ryland 1999
) apart from a single record from the north-eastern Adriatic Sea (
Novosel & Pozar-Domac 2001
). Therefore, if the Madeiran
Phaeostachys
population is not anthropogenically introduced, its arrival on the archipelago is likely to have occurred during glacial periods, with this ‘boreal guest’ staying for good.