Oncousoecia Canu, 1918

Taylor, Paul D. & Zatoń, Michał, 2008, Taxonomy of the bryozoan genera Oncousoecia, Microeciella and Eurystrotos (Cyclostomata: Oncousoeciidae), Journal of Natural History 42 (39 - 40), pp. 2557-2574 : 2560-2562

Genus Oncousoecia Canu, 1918

Type species

Oncousoecia lobulata Canu , 19185 Tubulipora lobulata sensu Hincks, 1880 , non Hassall, 1841, Recent, British Isles.

Diagnosis

Colony encrusting, unilamellar, oligoserial, branched, branches bifurcating regularly, sometimes developing lateral branches; all polymorphs fixed-walled with pseudoporous calcified exterior walls. Autozooids simple, tubular, apertures circular or elliptical, more or less regularly spaced, neither connate nor aligned in rows, peristomes moderate in length. Gonozooids longitudinally elongate, ovoidal, only slightly larger than an autozooid, the densely pseudoporous and bulbous brood chamber roof not penetrated by autozooidal peristomes; ooeciopore terminal or subterminal, circular or transversely elliptical, a little smaller than an autozooidal aperture; ooeciostome short, straight, not adnate to an autozooidal peristome. Kenozooids usually present along sloping branch edges, inconspicuous.

Remarks

Oncousoecia was introduced by Canu (1918) as the type genus of his new family Oncousoeciadae [sic], subsequently corrected to Oncousoeciidae by Canu and Bassler (1920). Canu (1918) gave the ‘‘genotype’’ (i.e. type species) as Tubulipora lobulata Hincks, 1880 . Unfortunately, Hincks was not the author of T. lobulata but rather gave a redescription of what he considered to be T. lobulata Hassall, 1841 . As pointed out by Hastings (1963), the true identity of Hassall’s species from Ireland is uncertain. However, Hassall’s illustrations ( Hassall 1841, Plate 10 Figures 1 , 2 ) of T. lobulata depict an encrusting cyclostome with broad, lobate branches and connate zooidal apertures arranged in uniserial rows diverging from the branch axes. This morphology matches more closely that of Tubulipora Lamarck, 1816 than Oncousoecia , which has apertures spaced apart in all species that have been attributed to the genus. No gonozooids are evident in Hassall’s figures. This is particularly unfortunate given the utility of these structures in cyclostome taxonomy. Indeed, Canu (1918) placed great taxonomic weight on gonozooids (‘‘ovicells’’), his diagnosis of Oncousoecia beginning (p. 325): ‘‘L’ovicelle est formée par une simple dilation longitudinale de la Péristomie des tubes. L’oeciostome est isolé et terminal.’’ In contrast, the gonozooids of Tubulipora are more complex and extend between the rows of autozooids (e.g. Hayward and Ryland 1985b).

As early as 1933 Osburn discussed the complex problem over the type species of Oncousoecia ( Osburn 1933) . Osburn, however, may not have had direct access to Canu (1918): a quotation attributed to Canu (1918) in fact comes from Canu and Bassler (1920, p. 687) and his statement that Canu (1918) reproduced Plate 61, Figure 5 of Hincks (1880) is also incorrect because the reproduced figure is actually in Canu and Bassler (1920, Figure 226A, B). To complicate matters yet further, Osburn (1933) followed written advice given to him by A. B. Hastings that T. lobulata sensu Hincks was a junior synonym of Alecto dilatans Johnston, 1847 (a species mistakenly attributed to Thomson by Osburn), and therefore cited A. dilatans as the ‘‘genotype’’ (type species) of Oncousoecia , an action interpreted by Hastings (1963) as lectotypification. As will be shown here, however, A. dilatans Johnston and T. lobulata sensu Hincks are not synonymous. Subsequent authors have been divided on how they have cited the type species of Oncousoecia . Some (e.g. Osburn 1953; Hastings 1963; Hayward and Ryland 1985b; Pitt and Taylor 1990; Taylor and McKinney, 2006) have followed Osburn (1933) in citing the type species as A. dilatans , while others (e.g. Bassler 1935, 1953; Buge 1957; Vavra 1977) have given it as T. lobulata Hassall, 1841 , or as T. lobulata Hincks, 1880 (e.g. Walter 1970).

Deciding which species is the valid type species of Oncousoecia depends on how one interprets the action of Canu (1918) when giving T. lobulata Hincks, 1880 as the type species. There are two possibilities: (1) Canu made a simple mistake in attributing the authorship of this species to Hincks rather than Hassall; or (2) Canu intended the type species of Oncousoecia to be T. lobulata sensu Hincks non Hassall. Option (1) constitutes incorrect citation, which, by application of Article 67.7 of the Code, would make T. lobulata Hassall, 1841 the valid type species of Oncousoecia . Option (2) is a deliberate misapplication of a name (Article 67.13), in which instance a new nominal species – Oncousoecia lobulata Canu, 1918 – can be considered to have been created at the time that Oncousoecia was erected by Canu. While a mistake (Option 1) by Canu (1918) in attributing authorship of T. lobulata cannot be ruled out entirely, we believe that Option (2) is more likely to be true, i.e. Canu (1918) deliberately chose T. lobulata sensu Hincks non Hassall as the type species for his new genus. Therefore, we consider that Canu (1918) effectively created a new species, Oncousoecia lobulata Canu, 1918 , when citing ‘‘ T. lobulata Hincks, 1880 ’’ as the type species of Oncousoecia . This option best serves taxonomic stability because it conserves popular usage of Oncousoecia for oligoserial encrusting tubuliporines with simple ovoidal gonozooids and non-connate autozooidal apertures.

Distribution

A large number of cyclostomes have been referred to Oncousoecia (see http:// www.bryozoa.net/cyclostomata/oncousoeciidae/oncousoecia.html). Described from the northern hemisphere (north-east Atlantic, Arctic, Gulf of Mexico, eastern Pacific), Oncousoecia is also present in New Zealand (Gordon et al. in press). The fossil record of the genus extends back to the Early Jurassic (Sinemurian) (see Taylor and McKinney 2006). Apart from the two extant species described here, Microecia occulta Harmelin, 1974 from the Mediterranean can be tentatively reassigned to Oncousoecia .

Figures

Figure 1. Photographs of type specimens of some Recent oncousoeciid cyclostome species. (A) Lectotype of Oncousoecia dilatans (Johnston, 1847) showing colony ramifying across the interior of a small bivalve shell (NHM 47.9.18.59). (B) Lectotype of Alecto compacta Norman, 1867, a subjective junior synonym of O. dilatans (NHM 11.10.1.63). (C) Lectotype of Oncousoecia lobulata Canu, 1918, the colony figured by Hincks (1880, Plate 50, Figure 5, 5a) as Tubulipora lobulata Hassall, 1841 which apparently formed the basis for Canu’s type species of Oncousoecia (NHM 1911.10.1.86). (D) Lectotype of Microeciella suborbicularis (Hincks, 1880), a subcircular colony with associated spirorbids (NHM 99.5.1.1427a). Scale bars: 5 mm (A, D); 1 mm (B, C).

Figure 2. Oncousoecia lobulata Canu, 1918, lectotype (NHM 1911.10.1.86). (A) Lobate, oligoserial branches; (B) autozooids; (C) gonozooid; (D) gonozooidal pseudopores showing partial occlusion by spines. Scale bars: 1 mm (A); 200mm (B, C); 50 mm (D).

Figure 5. Comparison of early astogeny in (A–C) Alecto compacta (Norman, 1867) [5Oncousoecia dilatans (Johnston, 1847)] (NHM 11.10.1.64) and (D–F) Microeciella suborbicularis (Hincks, 1880), two species formerly considered synonymous. (A) Ancestrula and first budded zooids; (B) ancestrula with short distal tube; (C) large protoecium with tiny pseudopores around perimeter (best seen top right); (D) fan-shaped young colony; (E) ancestrula with long distal tube; (F) protoecium with a few, non-perimetrical pseudopores and two larger, enigmatic punctures or borings (left). Scale bars: 500 mm (D); 200mm (A); 100 mm (B, E); 50 mm (C, F).