CALLOPORIDAE NORMAN, 1903

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 : 322-323

FAMILY CALLOPORIDAE NORMAN, 1903

Remarks: Spinose ovicells were first described by Ostrovsky & Taylor (2004) in three Cretaceous calloporid genera. Here we present a more detailed description of the structure of their ovicells.

GENUS DISTELOPORA LANG, 1915 DISTELOPORA BIPILATA LANG, 1915

( FIGS 3A- D , 21C , 24I, L )

Material: NHM D21876, D21879 -21883, D23019, Cretaceous, Lower Cenomanian, 10 ft (3.05 m) from the base of the Chalk Marl, Cambridge, England, F. Möckler Collection. NHM BZ4958 , Lower Cenomanian (? carcitanense Subzone), Porcellaneous Beds (= Chalk Marl), Barrington Chalk Pit, Cambridgeshire, England, A. N. Ostrovsky & P. D. Taylor Collection .

Description: Non-brooding autozooids (i.e. those that have no brood chamber on their proximal gymnocyst) possess 6–8 mural spine bases that indent the mural rim. These are usually paired, with the most proximal pair having the largest diameter and the distalmost pair (the oral spine bases) the smallest. The proximal part of the mural rim is usually devoid of spines ( Fig. 3A ).

Brooding autozooids positioned distally of maternal (egg-producing) zooids usually have six, sometimes seven, mural spine bases plus an additional 5–10 (usually 6–7) spines that constructed the ovicell. As with the mural spines, only the bases of the ovicell spines are preserved, the spines themselves always being broken off at their basal articulations and lost in these fossils. Ovicell spine bases are aligned in a distally convex arch on the proximal gymnocyst of the distal (brooding) autozooid ( Figs 3A- D , 24I, L ). This arch is normally gently curved ( Figs 3A, C, D , 24I ), but is occasionally more convex ( Fig. 3B , left ovicell), and a near semicircle of spine bases was found in one example ( Fig. 3B , right ovicell, 24 L). As a rule, the median ovicell spine bases are adjacent to the proximal edge of the mural rim of the distal zooid, and may slightly indent it ( Fig. 3D ). However, they can be also be positioned further from the mural rim ( Fig. 3C ). The outermost spine bases are always well-separated from the distal edge of the maternal zooid. The distance between adjacent ovicell spine bases is equal to or greater than their diameters. They have either approximately the same diameter as the most distal oral spines or are smaller. The floor of the ovicell, formed by the proximal gymnocyst of the distal zooid, is slightly concave.

DISTELOPORA LANGI OSTROVSKY & TAYLOR, 2004

( FIGS 4A , 21C , 24I )

Material: NHM D21873-21875, D21878, D23059, D23111, BZ4961 , BZ4962 , Cretaceous , Lower Cenomanian, 10 ft (3.05 m) from the base of the Chalk Marl, Cambridge, England, F. Möckler Collection .

Description: Non-brooding autozooids possess 9–11 (up to 16) mural spine bases, including usually four oral mural spines, though as many as six can be present. Proximal spine bases are typically slightly larger than distal spine bases. However, this character varies, and the largest spine bases can be any except for the most distal.

There are 10–12 mural spines in brooding (ooeciumbearing) zooids. Ovicell roofs were constructed of 7–8 spines borne on the proximal gymnocyst of the distal zooid ( Figs 4A , 21C , 24I ). The bases of these articulated spines typically have the same diameter as distal oral spines but can be somewhat smaller or larger. They are arranged in a gently curved, distally convex arch. The median spines are normally adjacent to the proximal edge of the mural rim of the distal zooid ( Fig. 4A ) but are sometimes separated from it by a narrow strip of gymnocyst. The outermost spine bases are always located far from the distal edge of the maternal zooid, and the distance between neighbouring ovicell spine bases is equal to or smaller than their diameter. The ovicell floor is slightly concave.

Figures

Figure 3. Distelopora bipilata Lang, Lower Cenomanian, Cambridge, England. A, part of a colony with several nonovicellate autozooids and one broken ovicell, NHM D21883. B, ovicell spine bases forming a semicircle, NHM D21881. C, ovicell spine bases at some distance from the mural rim, NHM D21881. D, ovicell spine bases forming a gentle arch. Medial spines are adjacent to the proximal edge of the mural rim of the distal zooid, NHM BZ4958. Scale bars: A = 100 Mm; B–D = 50 Mm.

Figure 4. A, Distelopora langi Ostrovsky & Taylor, fragment of a colony, with two broken ovicells showing ovicell spine bases in a gently curved arch; medial spine bases are adjacent to the proximal edge of the mural rim of the distal zooid. Lower Cenomanian, Cambridge, England, NHM D23111. B-D, Distelopora spinifera Ostrovsky & Taylor; Lower Cenomanian, Cambridge, England. B, part of a colony, showing spine bases of three ovicells; NHM D21651. C, ovicell spine bases arranged in a semicircle, the medial spines adjacent to the proximal edge of the mural rim of the distal zooid; NHM D21667. D, poorly preserved ovicell in which the medial spine bases are some distance from the mural rim of the distal zooid; NHM D21897. Scale bars: A, B = 100 Mm; C, D = 25 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.