Smittipora harmeriana ( Canu & Bassler, 1929 )

Dick, Matthew H., Ngai, Nguyen Danh & Doan, Hung Dinh, 2020, Taxonomy and diversity of coelobite bryozoans from drift coral cobbles on Co To Island, northern Vietnam, Zootaxa 4747 (2), pp. 201-252 : 211-212

Smittipora harmeriana ( Canu & Bassler, 1929)

( Fig. 5 A–C)

Velumella harmeriana Canu & Bassler, 1929: p. 128 .

Smittipora harmeriana: Winston & Heimberg 1986, p. 11 , figs 23–24; Hayward 1988, p. 281, Fig. 1c ; Tilbrook 2006, p. 76, pl. 12B.

Smittipora abyssicola: Harmer 1926, p. 259 , pl. 16, figs 10–13; not Smittipora abyssicola ( Smitt, 1873) .

Material examined. VNMN-0223 (CT-2), on SEM stub; VNMN-0224, six fragments.

Measurements. AzL, 0.51–0.79 (0.664 ± 0.075); AzW, 0.33–0.49 (0.429 ± 0.050); AzOpL, 0.15–0.21 (0.184 ± 0.015); AzOpW, 0.14–0.18 (0.163 ± 0.010); reproductive ZL, 0.60–0.81 (0.677 ± 0.059); reproductive ZW, 0.37–0.48 (0.426 ± 0.036); reproductive ZOpL, 0.20–0.29 (0.251 ± 0.026); reproductive ZOpW, 0.17–0.20 (0.185 ± 0.010); AvL, 0.44–0.59 (0.522 ± 0.043); AvW, 0.22–0.42 (0.305 ± 0.051); AvOpL, 0.17–0.27 (0.219 ± 0.024); AvOpW, 0.079 –0.133 (0.111 ± 0.018) (n = 15, 1).

Description. Colony unilaminar, encrusting, sheet-like.

Zooids irregularly semi-hexagonal proximally, rounded distally; distinct, delineated by sharp incision. Cryptocyst extensive, completely granulated, raised around margins to form rounded mural rim, depressed around and proximal to opesia, but forming broad median lip slightly turned up along proximal opesial margin, flanked by opesiular indentations. Inside opesia distally, below level of frontal surface, is a nearly semicircular shelf with straight proximal margin. Spines lacking. Opesiae campanulate in outline, dimorphic. Smaller opesiae slightly longer than broad, semicircular distally, widest proximally, with slight or marked opesiular indentations in proximolateral corners. Larger opesiae longer relative to width; opesiular indentations similarly variable.

Avicularia large, interzooidal, shorter and narrower than autozooids; truncate, rounded, or triangular distally, not curved; frontal surface like that of autozooids; opesia long-oval, often widest distally, with center of opesia at or distal to center of zooid; crossbar lacking; paired condylar socket on each side at top of mural rim flanking distal half of avicularian opesia.

Reproducing zooids have vestigial ooecium in form of small, semicircular cap immediately distal to orifice, outlined by distal groove and flanking sutures, often not evident in putatively reproducing zooids with large opesia; conversely, sometimes evident in presumably non-reproducing zooids with smaller opesia.

Remarks. Harmer (1926) considered this Indo-Pacific species to be conspecific with Smittipora abyssicola ( Smitt, 1873) , originally reported from the Caribbean region. Canu & Bassler (1929) realized it was not the same species as treated by Harmer and gave it a new name, Velumella (= Smittipora ) harmeriana , with no additional description. Harmer’s (1926) description and illustrations, which thus comprise the original description, well represent the material found at Co To. Harmer specifically mentions opesial dimorphism between reproducing and non-reproducing zooids, and his illustrations show diagnostic features seen at Co To, including the opesial dimorphism; avicularia that are shorter and narrower than autozooids, and truncate distally; the distal shelf inside the opesia; and the suture lines flanking the inconspicuous, often completely immersed vestigial ooecium. An important character in onychocellids is the nature of the avicularian mandible, which often consists of a median rachis with expanded ‘wings’ on one or both sides; unfortunately, the mandibles were missing in the Co To specimens. Tilbrook (2006) noted for material from the Solomon Islands that there is no opesial dimorphism, which is contrary to Harmer’s (1926) description and our observations of the Co To specimens. However, at Co To, while opesiae showed a bimodal size distribution, there was only a loose correlation between opesia size and presence of the reduced ooecium, with some zooids of each size having an ooecium.

Distribution. This species has a broad Indo-West Pacific distribution, having been reported from Mauritius ( Hayward 1988); Indonesia, Torres Strait, the Celebes, and Myanmar ( Burma) ( Winston & Heimberg 1986); Ceylon ( Sri Lanka), Queensland, and Singapore ( Harmer 1926); and the Solomon Islands ( Tilbrook 2006). The Co To record extends the previously known range (close to and south of the equator) northward nearly to 21°N.

Figures

FIGURE 1. Maps showing location of study area. Upper left, map of Southeast Asia; upper right, enlargement of box in upperleft panel, showing location of Co To archipelago (boxed) along northern coast of Vietnam; bottom panel, enlargement of box in upper-right panel, showing Co To archipelago. Black circle indicates location of collecting site.

FIGURE 5. A–C. Smittipora harmeriana (Canu & Bassler, 1929). A. Colony, VNMN-0223. B. Autozooids and interzooidal avicularia, with arrowhead indicating vestigial ooecium; VNMN-0223. C. Ancestrula (asterisk) and periancestrular zooids, along with Plesiocleidochasma porcellaniforme, VNMN-0256. D–F. Hippothoa sp. D. Parts of uniserial colony on bivalve shell, VNMN-0219. E. Autozooidal dilatation, showing cruciform branching and one proximolateral zooeciule, VNMN-0219. F. Autozooidal dilatation, showing orifice shape and slight frontal keel, VNMN-0217. Scale bars: A, 1 mm; B–D, 500 µm; E, F, 100 µm.