Pentapora lacryma, Lombardi & Taylor & Cocito, 2010

Lombardi, Chiara, Taylor, Paul D. & Cocito, Silvia, 2010, Systematics of the Miocene-Recent bryozoan genus Pentapora (Cheilostomata), Zoological Journal of the Linnean Society 160 (1), pp. 17-39 : 29-31

PENTAPORA LACRYMA SP. NOV. ( FIGS 9 , 10 )

Eschara pertusa Milne-Edwards, 1836 : Busk, 1859: 65 (part), pl. 10, figs 2a ′, 2b only.

Material examined: Holotype: NHM D50716, Coralline Crag Formation, Broom Hill, Suffolk, Burrows Collection . Paratypes: NHM BZ 5648-9, Pliocene, Coralline Crag Formation, Aldeburgh Member, Crag Pit Nursery, Aldeburgh, Suffolk, Bishop & Taylor Collection. NHM BZ 5677, Coralline Crag Formation, Aldeburgh Member, Aldeburgh Hall, Suffolk, Lombardi Collection, August 2007. NHM D50989, Coralline Crag Formation, Sudbourne Hall, Suffolk, Burrows Collection. NHM D50173-5, Coralline Crag Formation , Sudbourne Church , Suffolk, Burrows Collection. NHM D51060, Coralline Crag Formation , Crag Pit Nursery ( NGR 458580 ), Aldeburgh , Suffolk, Pitt Collection , 1967. NHM D55497, Coralline Crag Fm., Sudbourne Park Gates , Suffolk, Vallentin Collection . Other material: NHM BZ 5240, Coralline Crag Formation, Sudbourne Member , Crag Farm Yard , Suffolk, Tilbrook Collection , presented 1997. NHM BZ 5650-1, Coralline Crag Formation , Aldeburgh Member , Aldeburgh Hall , Suffolk, Tilbrook Collection , May 1994. NHM BZ 5652, Coralline Crag Formation , Crag Pit Farm , Suffolk, Tilbrook Collection , presented 1997. NHM BZ 5653, Coralline Crag Formation , Aldeburgh Member , Aldeburgh , Suffolk, Taylor Collection. NHM BZ 5654-6 (samples), Coralline Crag Formation , Crag Farm , Sudbourne , Suffolk, Whiteley Collection. NHM BZ 5657, Coralline Crag Formation , Sudbourne Member , Sudbourne , Suffolk, Taylor Collection , 1999. NHM BZ 5658, Coralline Crag Formation , Crag Farm , Sudbourne , Suffolk, Pitt Collection. NHM BZ 5659, Coralline Crag Formation , Richmond Farm , Gedgrave , Suffolk, Pitt Collection. NHM D34979, two specimens ( Fig. 10 ) questionably assigned to P. lacryma sp. nov., Pliocene, Red Crag Formation, Walton-on-Naze, Essex, Harmer Collection .

Diagnosis: Pentapora with erect foliaceous colonies; autozooids small, averaging 0.51-mm long by 0.27-mm wide; giant avicularia teardrop-shaped; ovicells with pores distributed over entire surface.

Description: Colonies developing three-dimensional, box-like growths comprising folded and anastomosing bilamellar plates from an extensive encrusting base that is often multilamellar. Diameter up to 12 cm ( NHM BZ 5240). Early astogenetic stages with smallsized zooids; ancestrula not clearly identifiable.

Autozooids longer than wide, 0.37–0.69 mm long (mean 0.53 ± 0.03 mm; N = 10), 0.13–0.41 mm wide (mean 0.27 ± 0.02 mm; N = 10), roughly rectangular in shape. Frontal shield lepralioid, slightly convex, granular, with areolar pores and pseudopores. Primary orifice longer than wide, 0.14 ± 0.18 mm long (mean 0.15 ± 0.02 mm; N = 5) by 0.11 ± 0.18 mm wide (mean 0.13 ± 0.03 mm; N = 5); condyles present; lappets present; closure plates occasionally developed ( Fig. 9E ). Oral spines seemingly lacking (although spine bases may have been obscured by epitaxial cement). Basal walls with short median septum extending distally from transverse wall. Ovicells wider than long, 0.16–0.24 mm long (mean 0.19 ± 0.02 mm; N = 20) by 0.19–0.28 mm wide (mean 0.24 ± 0.02 mm; N = 20), not embedded in the frontal shield of the distal zooid or overgrown; pores numerous, scattered over entire surface.

Avicularia dimorphic, adventitious, suboral, proximally directed; crossbar calcified. Normal avicularia small, 0.07–0.11 mm long (mean 0.09 ± 0.02 mm; N = 5), 0.05–0.08 mm wide (mean 0.07 ± 0.01 mm; N = 5), placed on an umbo normal to the frontal plane. Giant avicularia sporadically replacing normal avicularia, 0.20–0.27 mm long (mean 0.24 ± 0.02 mm; N = 15), 0.11–0.18 mm wide (mean 0.16 ± 0.02 mm; N = 15); rostrum spatulate, teardrop shaped; palate deep, broad; crossbar with columella.

Etymology: The species name (Latin, lacryma , tear) alludes to the shape of the giant avicularia.

Remarks: Some of the specimens assigned by Busk (1859) to Pentapora [as Eschara] pertusa from the Coralline Crag Formation in fact belong to P. lacryma sp. nov. It differs from P. pertusa in having numerous small pores scattered over the entire surface of the ovicell ( Fig. 9D ), whereas P. pertusa has a single large medial pore ( Fig. 8D ). A second striking difference is evident in specimens possessing giant avicularia. These are relatively small and teardrop shaped in P. lacryma sp. nov. ( Fig. 9A, D ), but are large, prominent, and triangular in P. pertusa ( Fig. 8B, F ). Although fragments of P. pertusa and P. lacryma sp. nov. can be found together in the same pieces of limestone matrix, suggesting that the two species lived in close sympatry, individual colony fragments always seen to have ovicells and giant avicularia characteristic of one species or the other – transitional forms are lacking. The identification of nonovicellate fragments without giant avicularia is, however, difficult, as noted above in the remarks for P. pertusa .

Distribution: Pliocene, Late Zanclean–Early Piacenzian, Coralline Crag Formation, Aldeburgh and Sudbourne members, questionably Ramsholt Member, Suffolk, UK and Red Crag Formation, Essex (note that many of the erect bryozoans in the Red Crag were derived and transported from the older Coralline Crag, which may be true of the specimens of? P. lacryma sp. nov. recorded here).

Figures

Figure 8. Pentapora pertusa (Milne Edwards, 1836), scanning electron micrographs of uncoated specimens from the Pliocene Coralline Crag Formation of Suffolk, England, imaged using back-scattered electrons. A, autozooids and several giant avicularia, Broom Pit, NHM D50182. B, ovicellate zooids and giant suboral avicularium with details obscured by diagenetic cement, Aldeburgh Member, Aldeburgh Hall, NHM BZ 5643. C–F, NHM BZ 5676,?Ramsholt Member, Broom Pit. C, patch of colony dominated by ovicellate zooids. D, ovicells and normal suboral avicularia. E, orifice and normal suboral avicularium. F, giant triangular suboral avicularium. Scale bars: A = 280 Mm; B = 190 Mm; C = 520 Mm; D = 220 Mm; E = 60 Mm; F = 100 Mm.

Figure 9. Pentapora lacryma sp. nov., scanning electron micrographs of uncoated specimens from the Pliocene Coralline Crag Formation of Suffolk, England, imaged using back-scattered electrons. A, ovicellate autozooids and giant avicularia partly obscured by diagenetic cement, Aldeburgh Member, Aldeburgh Hall, NHM BZ 5677. B, C, E, F, Aldeburgh Member, Crag Pit Nursery, Aldeburgh, NHM BZ 5648. B, autozooids from encrusting base. C, growing edge of encrusting base showing ovicellate zooids and a few giant avicularia. E, ovicellate zooids with closure plates and a giant avicularium (left). F, ovicell (pores obscured by diagenetic cement) and giant avicularium. D, holotype with ovicellate zooids showing evenly porous ooecia, Broom Hill, NHM D50716. Scale bars: A = 55 Mm; B = 240 Mm; C = 520 Mm; D = 230 Mm; E = 150 Mm; F = 130 Mm.

Figure 10.?Pentapora lacryma sp. nov., scanning electron micrographs of uncoated specimens from the Pliocene Red Crag Formation of Walton-on-Naze, Essex, England, imaged using back-scattered electrons. A, B, NHM D34979(a). A, autozooids and giant avicularia. B, broken ovicells and a giant avicularium (left). C, D, NHM D34979(b). C, autozooids with and without the outer aragonitic layer of the frontal shield. D, autozooid preserving the aragonite layer, sometimes merging across zooidal boundaries (arrow). Scale bars: A = 430 Mm; B = 210 Mm; C = 170 Mm; D = 160 Mm.