Gilbertopora, OSTROVSKY & TAYLOR, 2004

Ostrovsky, Andrew N. & Taylor, Paul D., 2005, Brood chambers constructed from spines in fossil and Recent cheilostome bryozoans, Zoological Journal of the Linnean Society 144 (3), pp. 317-361 : 325

GENUS GILBERTOPORA OSTROVSKY & TAYLOR, 2004

GILBERTOPORA LARWOODI OSTROVSKY & TAYLOR,

2004

( FIGS 5C- F , 21E , 24K )

Material: NHM D23297-23298, Cretaceous , Lower Cenomanian, 10 ft (3.05 m) from the base of the Chalk Marl, Cambridge, England, F. Möckler Collection. NHM BZ4954–4957 , same details but 20 ft (6.1 m) from the base of the Chalk Marl .

Description: Two small, knob-like oral spines occur in some of the nonbrooding autozooids. They have closed ends and were probably not basally articulated.

The ovicell roof is bipartite, constructed of two clawlike, arched, flattened spines ( Figs 5C- F , 21E , 24K ). These spines, which are not basally articulated, originate on the proximal gymnocyst of the distal (brooding) zooid which also forms the slightly concave floor of the ovicell. Basally, the spines are rather narrow and separate (similar to Wilbertopora mutabilis ; Ostrovsky & Taylor, in press) ( Fig. 24K ), but they broaden to become juxtaposed along the median line of the ovicell where a suture is developed ( Figs 5C, E, F , 21E ). The internal cavities of the two hollow spines seem not to be confluent, judging from an example in which the ovicell is broken along an apparent calcified wall between the juxtaposed spines. The ovicell has four openings: a distal opening is present between the bases of the two spines and has a teardrop-, oval or subcircular shape ( Fig. 5C, F ); two elliptical lateral openings (foramina) occur on each side of the ovicell between the arched spines and the floor of the ovicell ( Fig. 5D ); and the main, proximal opening of the ovicell is a wide, very low arch ( Fig. 5E ).

FAMILY MONOPORELLIDAE HINCKS, 1882

Figures

Figure 5. A, B, Unidistelopora krauseae (Voigt & Schneemilch), Lower Campanian, northern Germany, VC T10580. A, maternal zooid with ovicell and intramural bud. B, ovicell spine bases arranged in a semicircle along a ridge on the proximal gymnocyst of the distal zooid. C-F, Gilbertopora larwoodi Ostrovsky & Taylor, Lower Cenomanian, Cambridge, England. C, complete ovicell of two flattened spines; NHM D23297. D, complete ovicell viewed from the side, showing a lateral foramen; NHM D23298. E, complete ovicell in proximal view, showing the main opening of the ovicell; NHM D23298. F, complete ovicell in distal view, showing the distal opening; NHM D23298. Scale bars: A = 100 Mm; B-F = 50 Mm.

Figure 21. Schematic diagrams of brood chambers in Tendridae (A, B) and Calloporidae (C-E) in longitudinal and transverse section, showing maternal and distal zooids (fossil spinose ovicells reconstructed). A, Tendra zostericola. B, Heteroecium sp. C, Distelopora bipilata and D. langi. D, Distelopora spinifera, Unidistelopora krauseae. E, Gilbertopora larwoodi.

Figure 24. Schematic diagrams showing the shape of the mural rim and positioning of ovicell spine bases in frontal aspect; number of spines in Stichomicropora is approximate. Note that variable species may appear more than once. A, Stichomicropora sp. 1. B, S. oceani. C, Stichomicropora sp. 6. D, Stichomicropora sp. 1, S. sicksi and S. sulcata. E, S. oceani, Stichomicropora sp. 3, and Stichomicropora sp. 5. F, Stichomicropora sp. 6 and S. baccata. G, Stichomicropora spp. 1, 2 and 4, S. sicksi, S. sulcata, S. erecta, S. biconstricta, S. cf. clathrata and S. punctilla. H, S. marginula, Stichomicropora sp. 3; I, Distelopora bipilata and D. langi. J, Stichomicropora spp. 6 and 7, S. baccata, S. subquadrata, Monoporella spp. 1 and 2, M. prisca, M. nodulifera, and M. exculpta. K, Gilbertopora larwoodi or Wilbertopora mutabilis. L, Distelopora bipilata. M, Monoporella multilamellosa and M.? vincentownensis. N,?Thoracopora sp. and Craticulacella schneemilchae. O, Leptocheilopora tenuilabrosa, Leptocheilopora sp. 1, and Leptocheilopora sp. 2. P, Distelopora spinifera and Unidistelopora krauseae. R, Macropora spp.