LOWER CARBONIFEROUS BRYOZOA 
y AH/AW 
oe 
wil @ @ 
e @|MD1 
ADI | MD2 
— e 
AD2 | 
fig. 18 Measurements taken on rhomboporid and hyphasmoporid 
cryptostomes in this study: ZD = Width of zoarium measured 
perpendicular to growth direction; MD = Metapore diameter; MD1 = 
Metapore diameter measured parallel to growth direction; MD2 = 
Metapore diameter measured perpendicular to growth direction; AH = 
Acanthostyle height from base to tip; AW = Acanthostyle width 
measured at its base; AD1 = Autozooecia apertural diameter measured 
parallel to growth direction; AD2 = Autozooecia apertural diameter 
measured perpendicular to growth direction; IWT1 = Autozooecia 
apertural spacing measured parallel to growth direction; [WT2 = 
Autozooecia apertural spacing measured perpendicular to growth 
direction. Z1 = Number of autozooecial apertures contained in 1mm/?; 
Z2 = Number of autozooecial apertures contained within a 2mm line 
measured parallel to growth direction; AR = Number of autozooecial 
apertural rows measured around zoarium; ET = Endozone thickness; TE 
| =Exozone thickness. 
ncreasingly pyriform and equidimensional. This variation in 
jpertural size is reflected in apertural spacing; these two parameters 
apertural size and apertural spacing) are inversely proportional to 
ach other. Immediately after branching, elongate autozooecial 
pertures developed around the complete circumference of the 
aughter branch. Differentiation of apertural dimensions occurs 
a within two or three generations along the branch. 
| Interapertural walls are gently sinuous or occasionally straight 
nd may be raised to produce a ridge between apertural rows. One or 
wo rows of small short acanthostyles (0.02—0.04mm in diameter) 
re developed along this ridge. When two rows are present they are 
2parated by a distinct furrow. 
Autozooecial apertures are surrounded by 24 to 30 acanthostyles, 
various patterns. Commonly they flank only lateral margins and 
'p to six acanthostyles may occur proximal to apertures. Less 
Fensnity acanthostyles are arranged in a rhombic pattern, with 
nly one acanthostyle proximal to apertures. 
ISCUSSION. A complete systematic description of Rhabdomeson 
hombiferum is given in Wyse Jackson & Bancroft (1995a), as well 
5 a discussion of budding, branching and other features in 
nabdomesonids. 
Family RHOMBOPORIDAE Simpson, 1895 
| Genus RHOMBOPORA Meek, 1872 
YyPE SPECIES. Rhombopora lepidodendroides Meek, 1872 by 
129 
original designation, from the Upper Carboniferous of Nebraska 
City, Nebraska, U.S.A. 
Rhombopora cylindrica sp. nov. 
non 1841 = Millepora similis Phillips: 21, fig.32. 
non 1843 = Millepora similis Phillips; Morris: 42. 
1844 Millepora similis Phillips; M‘Coy: 196. 
non 1854 Ceriopora similis (Phillips); Morris: 121. 
1854b Millepora similis Phillips; M‘Coy: 104. 
1862 Millepora similis Phillips; Griffith: 196. 
1871  Ceriopora similis (Phillips); Young & Armstrong: 33. 
1876 Ceriopora similis (Phillips); Armstrong, Young & 
Robertson: 46. 
1877 Ceriopora similis (Phillips); Young & Robertson: 175. 
1881  Ceriopora similis (Phillips); Vine: 338. 
1885 Rhombopora similis? (Phillips); Vine: 93 pro parte. 
non 1887 Rhombopora persimilis Ulrich; Vine: 226, pl.1, fig.6. 
1887 Rhombopora similis (Phillips); Vine: 226, pl.1, fig.7. 
1889 Rhombopora similis (Phillips); Vine: 198. 
1987 Rhombopora similis (Phillips); Bancroft: 196. 
HOLOTYPE. BMNH PD9507; Upper part of the Glencar Lime- 
stone, Lower Carboniferous (Viséan, Asbian); Carrick Lough, County 
Fermanagh. 
Figs 19-25 
PARATYPES. BMNHPD9508-9534, 9576, upper part of the Glencar 
Limestone, Lower Carboniferous (Viséan, Asbian); Carrick Lough, 
County Fermanagh; Tavener-Smith and Wyse Jackson Collections. 
BMNH D294 (2 zoaria in a cavity slide of five), D295, Lower 
Carboniferous, Gayton Boring, Northamptonshire, England; Vine 
Collection. BMNH D303 (thin section of several zoarial fragments), 
Shales; Lower Carboniferous; Argyleshire, Scotland; Vine Collec- 
tion. TCD.28317, 28369, Nant-y-Gamar buildup, Llandudno Pier 
Dolomite Formation (Viséan, Asbian), near Llandudno, north Wales. 
TCD.34037-34044, 34122, 34126, 34128, 34165, 42592a, b; 
BELUM K2175, Upper part of the Glencar Limestone, Lower 
Carboniferous (Viséan, Asbian); Carrick Lough, County Ferman- 
agh; Wyse Jackson Collection. TCD.41515, Shales above Main 
Limestone, Pendleian, Upper Carboniferous, Hurst, near Richmond, 
Yorkshire, U.K. [NZ044 023], Bancroft Collection. TCD.42525- 
42528, Upper part of the Glencar Limestone (Viséan, Asbian), 
Sillees River, County Fermanagh, Wyse Jackson Collection. 
DERIVATION OF NAME. 
branches. 
From the cylindrical nature of zoarial 
DIAGNOSIS. Rhombopora with zoaria comprised of irregularly 
dividing, thin, cylindrical branches. Autozooecia are budded in a 
spiral manner from a central linear axis. The exozone region is thin. 
Autozooecial apertures are oval in shape, moderate to large in size 
and arranged in quincunx in longitudinal rows around branches. 
Metapores are rare and occur proximal to autozooecial apertures. 
Stylets are common and structurally varied: characteristically one to 
two acanthostyles may be situated at junctions of interapertural 
walls, and many small heterostyles occur in interapertural areas. 
DESCRIPTION. Colonies are composed of delicate, thin bifurcating 
branches. The largest fragment examined measures 16.2mm in 
length. 
Branches range in diameter from 0.54 to 1.15mm and retain a 
constant width along their length except prior to lateral branch 
development when a 25% increase in diameter occurs. Bifurcation is 
infrequent and irregular; lateral ramifications deviate at high angles 
of between 75° and 87°. 
Autozooecia are budded from a straight to undulatory central axis 
