Orectopora, Grischenko & Gordon & Melnik, 2018

Grischenko, Andrei V., Gordon, Dennis P. & Melnik, Viacheslav P., 2018, Bryozoa (Cyclostomata and Ctenostomata) from polymetallic nodules in the Russian exploration area, Clarion - Clipperton Fracture Zone, eastern Pacific Ocean-taxon novelty and implications of mining, Zootaxa 4484 (1), pp. 1-91: 15

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n. gen.

Orectopora   n. gen.

Type species. Orectopora flabellum   n. sp.

Etymology. Latinized form of Greek orektos, stretched out, plus - pora, a common suffix for cyclostome bryozoans. Gender feminine.

Diagnosis. Colony erect, flabellate, subplanar, attached by short stalk. Surface gently frontally concave with distinct abfrontal surface, typically with short bilaterally compressed fascicles; essentially two-layered, comprising, in transverse section, initially contiguous, but then laterally diverging, autozooidal tubes, backed by discontinuous series of narrower kenozooidal tubes. Gonozooid not seen. Colony supported by semi-erect ancestrula and a few daughter zooids, strengthened by basal kenozooids and extrazooidal calcification; no boundary between protoecium and peristome.

Remarks. Orectopora   n. gen. is exceptional among tubuliporines in having a bilaterally compressed colony in which zooidal apertures are confined to the distal margin in narrow subplanar fascicles backed by a discontinuous series of abfrontal kenozooidal chambers. Initial colony growth is reminiscent of that in Discantenna ( Gordon & Taylor, 2010)   , having an inclined ancestrular peristome and initial colony growth supported by a basal abfrontal skirt of kenozooids. Subsequent colony growth seems very different, however, forming an elevated unilaminar disk of frontally opening zooids in Discantenna   but a lobate fan of terminally opening zooids in Orectopora   . Alternatively, the outer convex side of the lobate branches might be equivalent to the abfrontal surface of cyclostomes such as Nevianipora   , such that the small zooids visible close to this face are the buds of autozooids (not kenozooids), which migrate towards the concave surface of the branches as they develop and become salient at the growing edge. This would explain the presence of some zooids of intermediate size that cannot be clearly identified as kenozooids or autozooids. If correct, this interpretation would likewise place Orectopora   n. gen. close to Discantenna   .

In the absence of a gonozooid, the family attribution of Orectopora   is uncertain.