Pentapora clipeus, 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 : 31-33

PENTAPORA CLIPEUS SP. NOV. ( FIG. 11 )

Material examined: Holotype: NHM BZ 5662, Middle Pliocene , Monte Padova (level 90), Castell’Arquato , Piacenza , Emilia, Italy, Pizzaferri Collection . Paratype: NHM BZ 5663, details as for holotype.

Diagnosis: Pentapora with erect bifoliate colonies; autozooids small, averaging 0.55-mm long by 0.37-mm wide; giant avicularia spatulate, often with closure plate containing two pores, crossbar uncalcified; ovicell with pores in a band close to orifice.

Description: Colonies erect, bilamellar, represented only by small fragments. Base and early astogeny unknown.

Autozooids small, longer than wide, 0.48–0.60 mm long (mean 0.55 ± 0.06 mm; N = 5), 0.33–0.42 mm wide (mean 0.37 ± 0.04 mm; N = 5). Frontal shield lepralioid, slightly convex, granular, with areolar pores and pseudopores; zooidal boundaries becoming less distinct during ontogeny. Primary orifice slightly longer than wide, 0.18–0.25 mm long (mean 0.22 ± 0.03 mm; N = 5), 0.17–0.22 mm wide (mean 0.20 ± 0.02 mm; N = 5); condyles present; lappets sometimes developed. Oral spines often present but few in number. Basal walls with short median septum extending distally from transverse wall. Ovicells globular, becoming completely embedded by calcification of the frontal shield of the distal zooid; pores present in a band close to the primary orifice.

Avicularia dimorphic, adventitious, suboral, proximally directed. Normal avicularia small, 0.07– 0.08 mm long (mean 0.080 ± 0.005 mm; N = 5), 0.06– 0.07 mm wide (mean 0.070 ± 0.006 mm; N = 5). Giant avicularia often substituting for normal avicularia, 0.17–0.27 mm long (mean 0.21 ± 0.03 mm; N = 15), 0.15–0.20 mm wide (0.17 ± 0.02 mm; N = 15), occupying less than half of the length of the autozooid, lying normal to the frontal plane partially within the primary orifice; rostrum spatulate; crossbar uncalcified; closure plates often present, containing two or occasionally three pores.

Etymology: The species name (Latin, clipeus , shield) alludes to the distinctive closure plates that occlude many of the giant avicularia.

Remarks: This new species is most easily recognized by the closure plates of the giant avicularia ( Fig. 11A– E ), structures that are not present in other species of Pentapora , except occasionally in P. lacryma sp. nov., where they lack the pores seen in P. clipeus sp. nov. The absence of a calcified crossbar in the giant avicularia is another distinctive feature ( Fig. 11C ): this does not seem to be simply the result of breakages, in view of the good condition of the material. Material of P. clipeus sp. nov. comes from a locality preserving aragonite, in contrast to most of the P. pertusa and P. lacryma sp. nov. specimens described above, where aragonite has been leached. This may account for the preservation of orificial lappets and secondary calcification overgrowing the ovicells ( Fig. 11B ). The new species shares with P. lacryma sp. nov. the possession of small autozooids. However, unlike the other fossil species of Pentapora , P. pertusa and P. lacryma sp. nov., ovicell pores are arranged in a band close to the primary orifice in P. clipeus sp. nov. ( Fig. 11A, B ); P. pertusa has single large ovicell pore ( Fig. 8A ), whereas numerous pores are scattered across the entire ovicell surface in P. lacryma sp. nov. ( Fig. 9D ).

Distribution: Pliocene, Piacenzian, Monte Padova, Emilia, Italy.

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 11. Pentapora clipeus sp. nov., scanning electron micrographs of uncoated specimens from the Middle Pliocene of Monte Padova, Castell’Arquato, Piacenza, Emilia, Italy, imaged using back-scattered electrons. A–D, holotype, NHM BZ 5662. A, colony fragment with zooids bearing giant avicularia. B, partly overgrown ovicell and two giant avicularia. C, giant avicularium; note the lack of a calcified crossbar. D, giant avicularium with closure plate containing two pores. E, paratype, NHM BZ 5663. E, orifice with left lappet preserved and giant avicularium with closure plate. F, primary orifice, normal suboral avicularium, and median septum and circular muscle impression visible on the basal wall of the broken zooid at the top left. Scale bars: A = 280 Mm; B = 100 Mm; D = 60 Mm; E = 50 Mm; F = 100 Mm.