LOWER CARBONIFEROUS BRYOZOA 
Fig. 15 Pseudonematopora planatus sp. noy. Line drawing of external 
features of BMNH PD9450; scale bar = | mm. 
Lidge developed between adjacent autozooecial rows. On the reverse 
surface the interapertural areas are slightly wider than those on the 
ybverse surface. A strong ridge may be developed there. 
Autozooecial apertures are small and circular. The apertures of 
he autozooecia adjacent to the reverse surface are divergent from it 
Fig. 11) and are marginally larger than those in other rows on the 
pbverse surface. Peristomes, situated proximally, are commonly 
: around apertures. Thin terminal diaphragms close off 
ome autozooecial apertures, behind which small circular brown 
bodies are found in chambers (Fig. 13b). These brown bodies, which 
fe similar in morphology to those reported by Morrison & Anstey 
1979) in some Ordovician trepostomes, represent the degenerated 
_ of the polypide soft tissues. 
able 5 Measurements of Pseudonematopora planatus (in mm), N=13. 
NM x Mn Mx CVw CVb 
W 130 0.80 0.61 1.20 7.80 7.96 
D1 130 0.18 0.10 0.26 10.84 8.60 
D2 130 0.13 0.10 0.23 14.74 6.08 
\S1 130 0.39 0.24 0.63 15.32 6.69 
\S2 130 0.18 0.10 0.41 26.97 5.65 
L2 130 3.6 3 5 11.31 13.50 
ISCUSSION. Pseudonematopora is reported from outside the CIS 
ormer Soviet Union) for the first time. In the County Fermanagh 
una P. planatus is quite common. Only three other species have 
reviously been recorded, all from Lower Carboniferous strata: P. 
etchorensis Gorjunova, 1985, the type species P. turkestanica 
227 
(Nikiforova, 1948) [Balakin, 1974], and P. balakini Gorjunova, 
1988. P. planatus differs from these three species in a number of 
respects. Zoarial width is narrower in P. turkestanica and the number 
of autozooecial rows is less. More importantly the autozooecial 
apertures in P. planatus are at least half the size as those of the other 
three species. Skeletal cysts are absent in P. planatus but may be 
developed in the other species. Terminal diaphragms have been 
reported from both P. turkestanica (Owen, 1966) and P. balakini 
(Gorjunova, 1988), and are present in P. planatus. 
Balakin (1974) noted that variation in zoarial width and fluctua- 
tion in the number of autozooecial rows in P. turkestanica are both 
large. P. planatus does not show such variation. Coefficients of 
variation for all measured parameters are low (Table 5). Variation 
within colonies is greater than variation between colonies in all 
features except zoarial width (ZW) and the number of autozooecia in 
a 2mm line (Z2). In these two cases variation within and between 
colonies is virtually identical. 
Rhombopora radialis Owen, 1966 is herein considered to be 
conspecific with Pseudonematopora turkestanica (Nikiforova, 1948). 
Comparison of Owen’s type material (LL.2984 holotype; LL.2985- 
2989 paratypes; Upper Viséan; Treak Cliff, Castleton, Derbyshire) 
with illustrations of Pseudonematopora turkestanica from the former 
Soviet Union (Balakin 1974) shows these taxa to have a similar 
morphology. Pseudonematopora is characterised by autozooecia 
budded from a central axis in an annular fashion, with short cham- 
bers and terminal diaphragms often developed, circular apertures 
with proximal peristomes, and a lack of acanthostyles and metapores. 
Conversely, Rhombopora zoaria are dendroid, with long autozooecia 
containing hemisepta, and with oval zooecial apertures, many 
acanthostyles, and occasionally metapores. 
Pseudonematoporais avery distinct genus witha straight, occasion- 
ally branching zoarium, autozooecia budded from a central axis, aper- 
tures with proximal peristomes, and occasional terminal diaphragms. 
Externally the taxon resembles the cystoporate Cheilotrypa Ulrich 
1884. However, internal structures and budding patterns in the two are 
quite different: inCheilotrypa diaphragms are present and autozooecia 
are budded from a central hollow axial tube (Utgaard 1983). 
Nematopora has been regarded as ancestral to Pseudonematopora 
(Balakin 1974) because the two taxa display a similar colony shape, 
autozooecial chamber shape, aperture size and shape, and budding 
pattern. However, in a computer-based phenetic study on the 
Rhabdomesina using cluster analysis of 44 features, Blake & Snyder 
(1987) suggested that Pseudonematopora was more closely related 
to Osburnostylus (88% similarity) than to Nematopora (78% simi- 
larity). Externally, however, Osburnostylus with rapid thickening of 
the zoarium at the level of the autozooecia apertures appears more 
different from Pseudonematopora than is Nematopora. Resolution 
of this phylogenetic problem may be achieved through finds of 
Pseudonematopora, extending its range, both geological and geo- 
graphical, and by more work on Palaeozoic bryozoans. 
STRATIGRAPHICAL RANGE. Lower Carboniferous (Viséan, Asbian). 
DISTRIBUTION. 
agh, Ireland. 
Carrick Lough and Sillees River, County Ferman- 
able 6 Quantitative comparison between Pseudonematopora species (dimensions in mm). 
| 
BW AR AD1 AD2 AS1 AS2 Z2 
_—_ sp. nov. 0.61—1.20 6-8 0.10-0.26 0.10-0.23 0.24-0.63 0.10-0.41 3-5 
) balakini Gorjunova, 1988 0.88-1.10 - 0.35-0.45 0.22-0.26 = - 4 
petchorensis 0.72-1.08 ~ 0.33-0.36 0.15-0.19 0.33-0.36 0.20-0.25 sy) 
| turkestanica (Nikiforova, 1948) 0.80—2.80 8-16 0.25-0.37 0.17-0.22 0.25-0.37 0.15-0.25 3-4 
ata from original sources. 
