Tricephalopora saillans ( 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 : 275-276

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

( Fig. 34 ; Table 7 )

Gephyrotes saillans Canu & Bassler 1920: 301 –302, pl. 5, figs. 18–20.

Material examined. Cotypes: USNM 63814 A– D, four specimens encrusting coralline algae, Danian (Paleocene), Alabama, USA. USNM 63814 C is chosen as lectotype.

Description. Colony encrusting, multiserial, unilaminar. Ancestrula and early astogeny not observed. Autozooids small, distinct, irregularly shaped, recalling a flying bee when viewed by light microscopy, longer than broad not including avicularia (mean L/W = 1.51). Frontal shield visible in a subcircular window, occupying less than half zooidal length, with 6, exceptionally 5 or 7, usually narrow (25–30 µm) irregularly spaced costae, the distalmost pair thicker (45–55 µm), lacking intercostal fusions. Costae converging and fused at zooidal midline along a narrow, elongated or rounded zone, adjacent costae separated by a single intercostal pore of variable size and shape; pelmatidia not observed in examined material. Primary orifice D-shaped to subcircular with slightly concave proximal margin, slightly broader than long (123 x 110 µm), hidden by raised peristome formed by band of smooth calcification derived from interzooidal kenozooids, leaving an arched lacuna between frontal shield and transversely elliptical secondary orifice. Avicularia adventitious, large, paired, resembling two lateral opened wings, each with swollen cystid, inclined and converging towards orifice, often contributing to formation of the distal rim; rostrum acutely triangular, more or less elongate, channelled and distomedially directed, with complete pivot bar. Ooecium subglobular, smooth, broader than long, immersed in distal zooid, opening deeply within peristome, barely visible in late ontogeny owing to secondary calcification spreading from kenozooids, and contributing to the formation of distal, arched peristomial rim together with avicularian rostra. Kenozooids responsible for swollen appearance of marginal portions of zooids, usually undefined, locally evident when broken.

Remarks. This species has been found encrusting coralline algae. Canu & Bassler (1920) assigned it to Gephyrotes , apparently because of the very salient peristome, although they do not describe the distal costae as bifurcated. They also reported the presence of a spiramen situated at the distal extremity of the costal field and discussed its potential function. A large arched lacuna is indeed present between the frontal shield and the secondary orifice but it is not a true spiramen. It is formed by the fusion of two wings of laminar calcification of kenozooidal origin. As observed by Taylor & McKinney (2006) in Tricephalopora lamellaria ( Canu & Bassler, 1926) , the above-mentioned characters and all other attributes of the species better conform to Tricephalopora . The two species have a generally similar aspect but differ in several features. Tricephalopora lamellaria (Fig. 35) has a very wide area of frontal shield exposed, the intercostal pores are very large and subquadrangular, there is a lessdeveloped kenozooidal network, avicularia differ in shape and position, and the lacuna between the frontal shield and the secondary orifice is filled by a band of calcification that leaves only two small circular pores. New SEM images of one of the cotypes of T. lamellaria (USNM69968 B) revealed the presence of a third adventitious avicularium, not described previously, placed distal to the orifice and directed proximally (Fig. 35).

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

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

Figures

FIGURE 34. Tricephalopora saillans (Canu & Bassler, 1920) n. comb., lectotype, USNM 63814 C, Danian (Paleocene), Alabama, USA: part of colony with most zooids having ooecia; note the typically large, distally converging oral avicularia. FIGURE 35. Tricephalopora lamellaria (Canu & Bassler, 1920), cotype, USNM 69968 B, Danian (Paleocene), Alabama, USA: basalmost autozooid has a third avicularium distal to the orifice, in addition to the paired avicularia described by previous authors. Scale bars: Fig. 34, 500 Μm; Fig. 35, 200 Μm.

Tables

TABLE 7. Measurements (in Μm) of Tricephalopora saillans (Canu & Bassler, 1920) n. comb., holotype, USNM 63814.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	3, 15	514	34	472–603
Zooid width	3, 15	340	56	271–437
Ovicell length	3, 4	186	1	185–186
Ovicell width	3, 4	229	10	218–238
Avicularia length	3, 20	187	31	142–240
Avicularia width	3, 20	108	17	81–136
Shield diameter	3, 10	194	32	158–247