Fig. 28 Mecynoecia suprabajocina sp. nov., MUZ PIG 1601/11/9. 
Oxfordian, Baltow, Poland. Scanning electron micrograph of branch 
growing tip showing spoke-like arrangement of zooecial walls, x 85. 
1953 
21967 
Apsendesia cristata Lamouroux; Bassler: 56, fig. 23,4. 
Apsendesia cristata Lamouroux; Walter: 46, pl. 10, figs 1— 
Dp 
Apsendesia cristata Lamouroux; Walter: 202, pl. 20, figs 6— 
11. 
1970 
MATERIAL. MUZ PIG 1601/II/6-7. 
DESCRIPTION. Colony erect, fungiform, a narrow stalk, about 0.8 
mm long, supporting an expanded, cup-shaped head, subcircular in 
plan view and averaging 4 mm in diameter (Figs 29-30). Autozooids 
grouped into fascicles which open around the circumference of the 
head and increase in number through bifurcation. Frontal side of 
head marked radially by ridge-like fascicles and convex frontal walls 
of autozooids. Underside of head an exterior wall with pseudopores 
and concentric growth lines, sometimes giving rise to downward- 
growing processes or struts each composed of about 3-6 zooids (Fig. 
Si): 
Autozooids long, lacking frontal walls and with polygonal aper- 
tures when situated in the centres of a fascicle, but possessing 
pseudoporous frontal walls and apertures with a curved external 
edge when situated at the border of a fascicle. Apertures about 0.15 
mm in diameter. 
Gonozooids not observed in specimens from Baltow (see below). 
REMARKS. This is one of the most distinctive of all Jurassic 
bryozoan species. At Baltéw only small colonies, resembling speci- 
mens from the French Bathonian described as Pelagia clypeata by 
Lamouroux (1821), have been found. Large colonies depart from a 
simple cup-shape and become complexly corrugated, like the speci- 
men described as Apsendesia cristata by Lamouroux (1821). 
The finding of A. cristata at Baltow in the Oxfordian extends its 
range upward from the Lower Callovian (Walter, 1970: 204). An 
apparent occurrence in the Upper Bajocian of Shipton Gorge (Walter, 
1967) is questionable: specimens from Shipton Gorge are extremely 
small, consisting of little more than a stalk and lacking the character- 
istic head and fascicles. 
The peculiar gonozooid of A. cristata, not found in specimens 
from Balt6w, is illustrated here using SEM for the first time (Fig. 
32). It develops within a cleft in a fascicle and has a small ooeciopore 
U. HARA AND P.D. TAYLOR 
situated in the centre of a bulbous frontal wall. Another unusual 
feature of A. cristata are the processes which may develop from the 
undersides of colonies (Fig. 31). These are multizooidal, originate at 
the growing edge (i.e. not by resorption of the exterior wall in more 
proximal sites), and may extend down to the substratum to form 
secondary supports for the colony. Voigt (1993) has described 
similar structures from a variety of other cyclostomes and 
cheilostomes. 
The Balt6w bryozoan fauna consists entirely of small, delicate 
colonies; there is a total absence of the larger, more robust 
cyclostomes, notably cerioporines, which characterize many other 
Jurassic bryofaunas. In this respect, the fauna resembles that found 
in the Upper Bajocian of Shipton Gorge (Walford, 1889, 1894; 
Walter, 1967), although known species diversity at Shipton Gorge is 
considerably greater (ca 19 spp., vs. 5 spp. at Baltow). Other — 
similarities between the two faunas include the abundance of 
bereniciform colonies with narrow axial canals, and the shared | 
presence of closely-related species of Mecynoecia (and possibly 
also Apsendesia cristata, but see note above). Walter (1967) inter- 
preted Shipton Gorge as a low energy, shallow water environmentin | 
which many of the bryozoans grew attached to thin algal filaments. 
A similar environmental interpretation probably also applies to 
Baltéw, as suggested by the bryozoans (see Maryanska & Koblinska, 
1980, 1984), corals (see Roniewicz & Roniewicz, 1971) and 
brachiopods (e.g. Barezyk, 1968, 1969, 1970). The presence of 
calcareous algae certainly implies deposition within the photic zone. 
Most specimens of H. baltovensis from Balt6w have tubular 
colonies with narrow axial canals (Figs 13-18). This colony-form is 
not, however, a specific character of H. baltovensis as some colonies 
are flat (Fig. 9). The presence of axial canals is clearly a result of 
encrustation of cylindrical substrates which were soft bodied and 
did not fossilize. Indeed, axial canals identical in size to those of H. | 
baltovensis can be found in sponges from Balt6w, which presum- 
ably lived attached to the same substrates as the bryozoans. 
Occasionally, the axial canals bifurcate, indicating that the organ- 
isms concerned had Y-shaped branches. Unfortunately, no informative |) 
bioimmurations of the surface details of the perished substrates are |) 
present on the basal laminae of the bryozoans. Therefore, the |} 
identity of the substrate is equivocal. Recent bryozoans can grow 
around a variety of cylindrical substrates of both plant and animal | _ 
origin. For example, Alvarez (1992: fig. 15) illustrated small colo- 
nies of the Recent cyclostome Disporella sp. growing around) 
un-named cylindrical substrates and leaving axial canals very simi- 
lar to those found in the Balt6w specimens. Bone & James (1993: ) 
fig. 7b) figured several different species of bryozoans attached to the 
cylindrical stems of sea-grasses from shallow water environments of |} . 
the Lacepede Shelf, southern Australia. Larger diameter axial canals)| _ 
result from growth of the cheilostomeSchizoporella floridana around) 
rhizomes of seagrass (see McKinney & Jackson 1989: fig. 7.12). 
Among living animals, the polychaete Phyllochaetopterus sociali 
living at depths beneath the photic zone on the Otago Shelf of New 
Zealand constructs long horny tubes about 1 mm in diameter. These 
tubes are fouled by a diversity of bryozoans, including encrustin 
cheilostomes and cyclostomes, as well as erect colonies of th 
cyclostomes Telopora and Hornera (P.D.T. unpublished). Colonies 
wrap around the circumference of the polychaete tubes. Tube decay 
would leave an axial canal in the centre of the colony. Some of the 
tubes divide, possibly as a result of asexual fission of the worms} 
| 
| 
| 
| 
| 
PALAEOECOLOGY 
| 
| 
io i 
