Gephyrotes spectabilis Canu & Bassler, 1920

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 : 270

Gephyrotes spectabilis Canu & Bassler, 1920

( Figs 23–25 ; Table 4 )

Gephyrotes spectabilis Canu & Bassler 1920: 303 , pl. 84, fig. 16.

Material examined. Holotype: USNM 64261, Early Oligocene, Mississippi, USA.

Description. Colony encrusting, unilaminar, multiserial ( Fig. 23 ). Ancestrula and early astogeny not observed. Autozooids distinct, with thin interzooidal furrows, arranged quincuncially, elliptical, longer than wide (mean L/W = 1.69). Gymnocyst not apparent. Frontal shield flat, formed by 8–12 costae, not including the 2 distalmost pairs participating in the proximal peristomial rim. Costae 25–35 µm broad, widely separated by a large (40–60 µm) elliptical lacuna and a much smaller (15–20 µm), usually subcircular, central intercostal lacuna ( Figs 24–25 ); two large, funnel-shaped, prominent pelmatidia on each costa ( Fig. 25 ). Proximal peristomial rim formed by conjunction of 2 pairs of costae, one pair originating from bifurcation of those most proximal to orifice and projecting frontalwards, the second pair originating lateral to orifice as a continuation of avicularian rostra, if present; collar-like structure exhibiting a transversely elongate, centrally placed intercostal lacuna and 2 subcircular lateral lacunae ( Figs 23–24 ). Primary orifice broader than long, semicircular with concave proximal margin ( Fig. 25 ); secondary orifice trapezoidal ( Fig. 24 ). Oral spines absent. Ooecium globular, small, wider than long, covered by expanding secondary calcification from most proximal costa of distal zooid, leaving a weakly calcified central patch ( Fig. 24 ). Adventitious avicularia large, paired, teardrop-shaped with complete pivot bar ( Fig. 24 ), lateral to the orifice, proximomedially directed. Hollow tubular kenozooids of irregular shape and size frequent along zooidal margins ( Figs 23–25 ).

Remarks. Gephyrotes spectabilis is very rare, with only one specimen having been found. The species is most similar in appearance to G. moissettei n. sp. They share the lace-like appearance of the zooids, the presence of two large avicularia placed lateral to the orifice and distomedially directed, and the diffuse presence of a kenozooidal network along lateral and distal margins of zooids. They differ in the number of costae and their thickness, and in the number and size of intercostal lacunae (two, very different in size in G. spectabilis vs three equally sized in G. moissettei ). Furthermore, G. spectabilis lacks a gymnocyst, and has very distinctive pelmatidia.

Distribution. Early Oligocene of Mississippi, USA ( 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 23 – 25. Gephyrotes spectabilis Canu & Bassler, 1920, holotype, USNM 64261, Early Oligocene, Mississipi, USA: 23, general appearance of colony, which roughly resembles that of G. moissettei n. sp.; 24, reproductive zooids; note the outer layer of ooecial frontal calcification that is produced by distal zooids; 25, autozooids, some showing the entire primary orifice; note the intercostal lacunae and pelmatidia and broken tubular kenozooids occupying interzooidal boundaries. FIGURE 26. Gephyrotes moissettei n. sp., holotype, PMC. B 18.6.9.2006 a, late Tortonian, Calabria, Italy: autozooids (for comparison with those of G. spectabilis). Scale bars: Fig 23, 500 µm; Figs 24 – 26, 200 µm.

Tables

TABLE 4. Measurements (in Μm) of Gephyrotes spectabilis Canu & Bassler, 1920, USNM 64261.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	1, 10	509	28	464–561
Zooid width	1, 10	301	32	245–349
Orifice length	1, 6	105	4	101–110
Orifice width	1, 6	146	24	123–172
Ovicell length	1, 8	135	28	104–175
Ovicell width	1, 8	213	26	179–258
Avicularia length	1, 10	127	12	106–145
Avicularia width	1, 10	84	8	68–100