Gephyrotes quadriserialis 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 : 271-273

Gephyrotes quadriserialis Canu & Bassler, 1920

( Figs 27–29 ; Table 5 )

Gephyrotes quadriserialis Canu & Bassler 1920: 304 , pl. 42, figs 4–5.

Material examined. Cotypes: USNM 64031 A–B, two specimens, Late Eocene, Florida, U.S.A. USNM 64031 A is chosen as lectotype.

Description. Colony erect with cylindrical branches, these formed by 4 alternating longitudinal rows of zooids and bifurcating at an angle of about 90° ( Figs 27–28 ). Autozooids distinct, with deep interzooidal furrows, elliptical, elongate (mean L/W = 1.78). Gymnocyst not apparent. Frontal shield convex, formed by 16–21 costae, not including the 2 distalmost pairs participating in the proximal peristomial rim. Costae 45–55 µm broad, fused centrally, separated by a narrow fissure laterally. Number of pelmatidia uncertain because of preservational state; at least 2 small circular pelmatidia visible in some costae. Proximal peristomial rim formed by conjunction of two pairs of elevated costae, one pair originating from bifurcation of those most proximal to orifice and projecting upwards, the second pair originating lateral to orifice; this collar-like structure exhibiting a subcircular central intercostal lacuna that is more proximally placed than the 2 smaller subtriangular ones laterally ( Fig. 29 ). Primary orifice D-shaped, with straight or slightly concave proximal margin ( Fig. 29 ); secondary orifice elliptical ( Fig. 29 ).

Oral spines absent. Tubular, hollow kenozooids along zooidal margins, responsible for narrow rim of peripheral calcification ( Figs 27, 29 ). Avicularia and ooecia not observed.

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

Remarks. Gephyrotes quadriserialis is very distinctive because of its erect colony growth form and the presence of a continuous series of kenozooids along the zooidal margins. This latter feature, although shared with other species of the genus and overlooked in the original description, is here particularly developed, giving the impression of a marked distance between zooids. The general appearance of the frontal shield, with numerous broad costae very close to each other, resembles that of G. convexus (see below), as already suggested by Canu & Bassler (1920). Besides the above-mentioned characters, the two species differ also in the absence of avicularia in G. quadriserialis . However, further material is needed to assess if the lack of avicularia is real or apparent, a feature that Canu & Bassler (1920) mentioned in addition to the colony morphology as possibly excluding this species from Gephyrotes . Intercostal bridges are a further character typical of the genus missing in G. quadriserialis .

Nevertheless, the development of the collar-like peristomial complex from the two distalmost pairs of costae, one of which bifurcates, as well as the kenozooidal network, perfectly accords with the definition of the genus. Distribution: Late Eocene of Florida, USA.

Figures

FIGURES 27 – 29. Gephyrotes quadriserialis Canu & Bassler, 1920, lectotype, USNM 64031 A, Late Eocene, Florida, USA: 27, a typical quadriserial branch at a bifurcation; kenozooids along zooidal boundaries are particularly elongate; 28, a long, straight fragment; 29, close-up of Fig. 28 to show the multicostal frontal shield, peristomial collar-like structure and extensive development of kenozooids. Scale bars: Figs 27 – 29, 500 Μm.

Tables

TABLE 5. Measurements (in Μm) of Gephyrotes quadriserialis Canu & Bassler, 1920, USNM 64031.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	2, 14	628	49	552–731
Zooid width	2, 14	352	35	288–397
Orifice length	2, 6	96	5	91–103
Orifice width	2, 6	125	10	110–139