Exechonella rimopora, 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 : 63-65

Exechonella rimopora n. sp.

( Fig. 26 , Table 25)

Coleopora verrucosa: Winston & Heimberg 1986 , p. 15, 16, figs 33‒34.

Material examined. Holotype: USNM 545931 (colony encrusting coral fragment together with USNM 7915 , Hiantopora bidenticulata Canu & Bassler, 1929 ). Philippines, Sirun Island, Sulu Archipelago, Albatross Station D. 5151, 5° 24’ 40” N, 120 ° 27’ 15” E, depth 24 fathoms, 18 February 1908.

Etymology. The name reflects the slit-like shape of the luminae of the frontal foramina in this species. Derived from the Latin word “rima” (slit).

Description. Colony encrusting, unilaminar, multiserial. Autozooids convex, oval or pentagonal in shape, separated by deep grooves. Primary orifice oval, wider than long, poster (one third) slightly narrower than the anter (two thirds). Distal part of primary orifice is underlain by an inner lamina, which ends in drop-like condyles pointed to the orifice midline or downward. Orifice with proximal shelf (a distalmost part of the zooidal frontal shield proximally surrounded by a wall of the peristome) that has a slight convex or smooth area in its central part. Areas to the left and to the right from this convex/smooth area are wrinkled. Peristome short, tubular, flared out, with pustulose external surface. Its proximal part is often wider. Frontal shield slightly pustulose being perforated by 52–75 small slit-like foramina. Most of the foramina are situated in a small depression whereas some are on the top of short, elevated and flattened tube. Autozooids possess 6–11 long, spire-like, thick-walled hollow processes randomly distributed across the frontal shield. Small oval marginal pores well seen around zooidal periphery. Vertical zooidal walls narrow, represented by mural septula. Avicularia are associated with two largest foramina having lateralmost or sometimes proximolateral position. Each avicularium has a central nipple-like structure with a central pore, surrounded by tall, flat and wavy foraminal rim. Kenozooids are abundant, being recognized by 2–4 small pores. These are often associated with avicularia. Ancestrula is unknown.

Philippines

m±sd r n AzL 819±73.03 744–967 7 AzW 615.3±29.51 564–652 7 OrL 175.4±10.8 158–186 5 OrW 193.2±6.61 186–201 5 FoN 65±8.4 52–75 6 PeL 313.3±14.1 301–331 4 PeW 301.3±21.2 270–317 4 Remarks. Exechonella rimopora n. sp. belongs to E. verrucosa -complex, because of their special frontal wall with hollow projections. The new species is characterized by its frontal shield slightly pustulose being perforated by numerous small, slit-like foramina. It strongly reminiscent E. kleemanni n. sp., differing from it by several characters. (1) Although both species have slit-like foramina, they are mainly located in a shallow depression, and only rarely on the top of the flattened tubes that is typical of E. kleemanni n. sp.; (2) foramina are more numerous in E. rimopora n. sp. (52–75 vs 31–56 in E. kleemanni n. sp.), and (3) the former species has smaller zooids than the latter (819×615 µm in E. rimopora n. sp. and 1048× 783 in E. kleemanni n. sp.).

Our specimen totally corresponds to the colony from the Komodo Island, Indonesia, described and figured by Winston and Heimberg (1986) as Coleopora verrucosa . We consider them as con-specific.

Distribution. Initially found in Philippines, this species extends its distribution to Indonesia.

Figures

FIGURE 26. Exechonella rimopora n. sp. Philippines (A ‒ I: holotype USNM 545931). A, C, general view of the upper (A) and the lower (c) parts of holotype from above. B, close-up of several autozooids on the colony periphery (some lateralmost foramina with avicularia shown by arrows). D, E, details of primary orifice and peristome. F, G, close-up of autozooids (lateralmost foramina with avicularia shown by arrows). H, I, close-up of lateralmost foramina with avicularia. Scale bars: A, C = 500 µm; B, D, E = 100 µm; F, G = 200 µm; H, I = 50 µm.