Gephyrotes fortunensis Pouyet, 2000

Martino, Emanuela Di & Rosso, Antonietta, 2015, Revision of the bryozoan genus Gephyrotes Norman, 1903 (Cheilostomata, Cribrilinidae) with the description of two new taxa, Zootaxa 3941 (2), pp. 261-283 : 265-267

Gephyrotes fortunensis Pouyet, 2000

( Figs 9–12 ; Table 2 )

Gephyrotes fortunensis Pouyet 2000: 186 , figs i, k; Berning 2006: 53 –54, figs 48–49.

Material examined. Holotype: FSL 117925 late Tortonian, Fortuna (Murcie, Spain).

Description. Colony encrusting unilaminar, multiserial ( Fig. 9 ). Ancestrula and early astogeny not observed. Autozooids distinct, with deep interzooidal furrows, oval (mean L/W = 1.61). Gymnocyst smooth, forming steeply inclined marginal portions of frontal shield, usually visible only proximally. Frontal shield relatively flat, formed by 8–10 costae, more often 9, not including 2 distalmost pairs participating in proximal peristomial rim. Costae 55–75 µm broad, separated by 2–3 intercostal pores, 35–45 µm broad, with 2–4 pelmatidia on each costa, the marginal ones prominent, giving to central part of frontal shield a flatter appearance ( Fig. 11 ). Proximal peristomial rim formed by conjunction of two pairs of raised costae, one pair originating from bifurcation of those most proximal to orifice and projecting upwards, the other pair rising distolateral to orifice; this collar-like structure having centrally a pointed-arch intercostal lacuna and 2 elongated lateral lacunae ( Fig. 10 , upper left side). Primary and secondary orifice broader than long, semicircular. Oral spines not observed. Tubular structures visible lateral to orifice ( Fig. 10 , upper part), either small and longitudinally elongate or large and transversely elongate, converging in midline and arching over orifice proximally; they probably correspond to distalmost part of broken costae. Presence of definite avicularia uncertain. Ooecium prominent, subglobular, wider than long, with irregularly shaped patches, possibly corresponding to weaker areas prone to breakage.

Remarks. The holotype is characterized by several irregularly shaped zooids that have long 'tails' of gymnocyst as seen in G. nitidopunctatus , probably as an adaptive response to the irregularities of the encrusted substratum or as a result of regeneration after breakage. In the original description, Pouyet (2000) mentioned a large, curved avicularium on each side of the orifice, distally directed. We agree with Berning (2006) in interpreting their apparent presence as an artefact produced by the breakage of the distalmost pair of costae forming the collar-like structure. We similarly interpret the two hollow structures pointing across the orifice proximally in a few zooids ( Fig. 10 ), as well as the two oral spine bases described by Pouyet (2000), located at the corners of the orifice, which exactly correspond to the raised points of the distalmost pair of costae ( Figs 11–12 ). Pouyet (2000) described and figured an ooecium with a median ridge between two fenestrae. Again, we agree with Berning (2006) that these characters and other irregularities derive from mechanical breakage or partial dissolution of a normally subglobular ovicell ( Figs 10–11 ). Specimens of G. fortunensis figured by Berning (2006) show a similar number of costae but a more extensive gymnocyst compared to the type specimen. In addition, Niebla material is better preserved than the holotype, allowing a more precise description of the frontal shield and of the collar-like construction associated with the orifice. Gephyrotes fortunensis differs from the type species G. nitidopunctatus in the appearance of the frontal shield, with a flat central area bordered by a raised rim formed by the prominent proximal portions of the costae. Further differences include the smaller extent of the kenozooidal network. The absence of avicularia cannot be effectively considered as a difference owing to the preservation of the specimens. Berning (2006) also cited peripheral papilla pores as a difference between G. nitidopunctatus and G. fortunensis ; these have an elongated slit-like form, lie parallel to the costae and result from the absence of an outer row of costal fusions. This distinction is difficult to ascertain.

Gephyrotes fortunensis is rare; a dozen specimens were found by Pouyet (2000) in the Fortuna deposits encrusting oyster shells and scleractinian corals of the genus Porites , while only three specimens were found by Berning (2006) in the Niebla Calcarenite encrusting coralline algae.

Distribution. Late Tortonian of the Murcia and Guadalquivir Basins, SE and SW Spain ( Fig. 1 ).

N, Number of colonies and number of zooids measured; SD, standard deviation.

Figures

FIGURE 1. Map showing the spatial and temporal distribution of all the studied species. 1, Gephyrotes nitidopunctatus (Smitt, 1868); 2, Gephyrotes fortunensis Pouyet, 2000; 3, Gephyrotes moissettei n. sp.; 4, Gephyrotes spectabilis Canu & Bassler, 1920; 5, Gephyrotes quadriserialis Canu & Bassler, 1920; 6, Gephyrotes convexus Canu & Bassler, 1920; 7, Tricephalopora saillans (Canu & Bassler, 1920); 8, Tricephalopora levigata (Canu & Bassler, 1920); 9, Spiniflabellum spinosum Canu & Bassler, 1928. Open circles, Recent; solid circles, Miocene; diamond, Oligocene; stars, Eocene; triangles, Danian.

FIGURES 9 – 12. Gephyrotes fortunensis Pouyet, 2000, holotype FLS 117925, late Tortonian, Fortuna (Murcie, Spain): 9, aspect of the colony with irregularly budded zooids caused by the roughness of the substratum and possible post-breakage regeneration; 10, autozooids, several (upper part) with variously preserved collar-like orificial structures, and a single ooecium (upper left); 11, close-up of the left side of fig. 9 with one zooid bearing an ooecium; 12, autozooids showing costate shields with lacunae and pelmatidia; collar-like orificial structures broken. Scale bars: Figs 9, 10, 1 mm; Figs 11, 12, 500 Μm.

Tables

TABLE 2. Measurements (in Μm) of Gephyrotes fortunensis Pouyet, 2000, holotype, FSL 117925.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	1, 10	636	72	538–741
Zooid width	1, 10	394	31	332–449
Orifice length	1, 5	137	9	130–143
Orifice width	1, 5	196	17	184–208
Ovicell length	1, 2	277	47	244–311
Ovicell width	1, 2	322	54	284–361
Avicularia length	1, 4	98	6	91–103
Avicularia width	1, 4	56	3	54–58