Exechonella panamensis, Cáceres-Chamizo & Sanner & Tilbrook & Ostrovsky, 2017

Cáceres-Chamizo, Julia P., Sanner, Joann, Tilbrook, Kevin J. & Ostrovsky, Andrew N., 2017, Revision of the Recent species of Exechonella Canu & Bassler in Duvergier, 1924 and Actisecos Canu & Bassler, 1927 (Bryozoa, Cheilostomata): systematics, biogeography and evolutionary trends in skeletal morphology, Zootaxa 4305 (1), pp. 1-79 : 34-35

Exechonella panamensis n. sp.

( Fig. 13 , Table 12)

Exechonella antillea: Hughes & Jackson 1992 , p. 453. Exechonella antillea: Winston 1986 , p. 19, fig. 40.

Material examined. Holotype: USNM 545919, on a piece of coral. Caribbean Sea, San Blas Archipelago, Holandes Cays, depth 15–20 m, collected between July 1987 and May 1988 ( Hughes & Jackson 1992).

Etymology. Named after the Isthmus of Panama, near which coast this species has been found.

Description. Colony encrusting, unilaminar, multiserial. Autozooids hexagonal or sometimes oval in shape, separated by well-defined narrow grooves. Zooidal periphery surrounded by a narrow gymnocystal rim. Primary orifice suboval, wider than long, poster (one-third) predominantly with angular outline, slightly narrowing proximally. Anter (two-thirds) with rounded outline, its wall underlain by an inner lamina which ends form tiny condyles, rounded or triangular. Step-like curved area below condyles ill-defined. A low peristome, narrow-walled, with 5–7 long, thin hollow spikes, proximally forming smooth and flat band. Typically there six spikes in a peristome, three distal, slender, and two lateral and one mid-proximal that are more robust. Lateral and proximal spikes bifurcate in some zooids. Frontal shield smooth, perforated by 56–67 closely spaced foramina, each with wide and smooth gymnocystal rim with walls slightly above the frontal shield and slightly sloping towards a central opening. Fusions between foraminal rims of 2–4 (up to 5) are frequent. Ten to 23 long, thin and hollow spikes, mostly straight, but some slightly curved, arise from foraminal rims, often where they fuse with each other. Marginal pores are mostly oval and elongated. Small nipple-like conic avicularia are present on the outer raised rim of two lateralmost foramina. Gymnocystal rim of such foramina bears a thin spike. Kenozooids were not seen. Vertical zooidal walls wide, represented by multiporous mural septula with 2–3 rows of communication pores. Ancestrula is unknown.

San Blas Archipelago, Caribbean Sea

m±sd r n AzL 1202±123.4 955–1499 15 AzW 1009.2±110.7 706–1156 15 OrL 270±17 242–302 20 OrW 368±21.1 305–397 20 FoN 61±4.0 56–67 10 FoD 110±10.4 85–139 36 OD 39±6.15 28–54 36 Remarks. For the first time this species was illustrated by Winston (1986) (as E. antillea ). Exechonella panamensis n. sp differs from the other species of E. antillea -complex by its hollow spikes (projections) that arise from the foraminal rims on the frontal wall and also around the peristome, as well as by its small condyles. Distribution. At present, the species has been recorded in Caribbean Sea, San Blas Archipelago, near Panamanian coast, and Río Bueno, Jamaica.

Figures

FIGURE 13. Exechonella panamensis n. sp. Caribbean Sea, San Blas Archipelago (A ‒ F: holotype USNM 545919). A ‒ D, general view of holotype from above. In B and D some avicularia associated with lateralmost foramina shown by arrows. E, F, close-up of autozooids showing shape of primary orifice. Avicularia shown by arrowheads. Scale bars: A, C = 1 mm; B, D, = 500 µm; E, F = 200 µm.