Tricephalopora levigata ( Canu & Bassler, 1920 ) 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 : 276-277

Tricephalopora levigata ( Canu & Bassler, 1920) n. comb.

( Figs 36–39 ; Table 8 )

Gephyrotes levigatum Canu & Bassler, 1920: 301 , pl. 6, fig. 1.

Material examined. Cotypes: USNM 63816 A–D, four specimens encrusting shells, Danian (Paleocene), Georgia, USA. Two of four specimens (C–D) are assigned to this species. USNM 63816 C has been chosen as lectotype.

Description. Colony encrusting, multiserial, unilaminar ( Fig. 36 ). Ancestrula and early astogeny not observed. Autozooids small, distinct, with deep interzooidal furrows, irregularly shaped ( Figs 37–38 ), recalling a flying bee when viewed by light microscopy, longer than broad not including avicularia (mean L/W = 1.58). Frontal shield visible in a subcircular window ( Fig. 39 ), occupying less than half zooidal length, with 5–7 barely distinct, narrow (25–30 µm) costae lacking intercostal fusions. Costae converging and fused at zooidal midline, adjacent costae separated by a single intercostal pore of variable size and shape, mostly like a fissure; pelmatidia not observed in examined material. Primary orifice D-shaped to subcircular with slightly concave proximal margin, slightly broader than long (122 x 103 µm), hidden by raised peristome formed from band of smooth calcification derived from interzooidal kenozooids, leaving an arched, triangular lacuna between frontal shield and the secondary orifice ( Figs 38–39 ). Secondary orifice semicircular. Adventitious avicularia, small, paired, oval, converging towards orifice, resembling laterally opened wings; rostrum rounded, distomedially directed, with complete pivot bar ( Fig. 39 ) and small swollen cystid. Ooecium immersed in distal zooid, broader than long, proximally bordered by slightly prominent distal margin of orifice. Kenozooids responsible for calcification covering marginal portions of the zooids, usually undefined, locally evident when broken.

Remarks. This species has been found encrusting molluscan shell. Tricephalopora levigata differs from T. saillans in having smaller zooids and avicularia. Canu & Bassler (1920) mentioned also the lack of a pivot bar as a further difference between these two species despite inking it on the figured specimens. Nevertheless, this feature is clearly visible in the SEM images. Two of four cotypes have a different aspect (see Fig. 40), as already noticed by Canu & Bassler (1920, pl. 6, figs 2–3). Nevertheless, the authors accommodated these specimens within the range of variability, mainly based on the measurements of avicularia and ovicells. In our opinion, observed differences, including the aspect of the frontal shield, are more relevant than the similarities, and we excluded them from the present species. Unfortunately, the poor preservation of the specimens prevents a complete description. The attribution of these specimens to the genus Tricephalopora is questionable.

Distribution. Danian (Paleocene) of Georgia, U.S.A.

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

Figures

FIGURES 36 – 39. Tricephalopora levigata (Canu & Bassler, 1920) n. comb.; Figs 36 – 39, lectotype, USNM 63816 C, Danian (Paleocene), Georgia, USA; Fig. 40, USNM 64816 A, reported as cotype by Canu & Bassler (1920): 36, general appearance of the colony; 37, fertile autozooids; 38, sterile autozooids with paired oral avicularia; 39, close-up of an autozooid to show the centrally exposed frontal shield and an avicularium with a complete pivot bar; FIGURE 40.? Tricephalopora sp., autozooids with entirely exposed frontal shields. Scale bars: Fig. 36, 500 Μm; Figs 37 – 40, 200 Μm.

Tables

TABLE 8. Measurements (in Μm) of Tricephalopora levigata (Canu & Bassler, 1920) n. comb., holotype, USNM 64816.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	2, 10	422	41	376–484
Zooid width	2, 10	266	25	235–303
Ovicell length	2, 5	111	9	98–120
Ovicell width	2, 5	209	10	197–224
Avicularia length	2, 10	125	6	116–130
Avicularia width	2, 10	77	6	72–87
Shield diameter	2, 10	159	13	139–178