Filellum annulatum ( Watson, 1973 )

Marques, Antonio C., Peña, Álvaro L., Miranda, Thaís P. & Migotto, Alvaro E., 2011, Revision of the genus Filellum Hincks, 1868 (Lafoeidae, Leptothecata, Hydrozoa), Zootaxa 3129, pp. 1-28 : 7-8

Filellum annulatum ( Watson, 1973)

Reticularia annulata Watson, 1973: 164 , figs. 5–6.

Filellum annulatum: El Beshbeeshy 1991: 71 –73, figs. 15a–b; Peña Cantero et al. 1998: 299. Non Corystolona annulata: Watson 2002: 334 –335, figs. 1a–e.

Type series. Holotype—“ NMV G1922, microslide; G2091, preserved material, remainder of holotype colony–S [denoting the sheltered side of Pearson Island], 17 m, on a small calcareous bryozoa” ( Watson 1973: 164). Type material was not examined.

Type locality. From the holotype, sheltered side of Pearson Island, Great Australian Bight ( Watson 1973).

Remarks. Watson (1973) described and figured Reticularia annulata as a new species assigned to the family Lafoeidae . When Reticularia was recognized as a preoccupied name for a brachiopod, the species referred to this genus were assigned to the genus Filellum by Peña Cantero et al. (1998) (see discussion above). Watson (1973: 164) characterized her species “by the close thecal rings […] of uniform size, and the distance between them varies little along the entire length of the hydrotheca. They have developed by continuous apical reduplication during growth of the hydrotheca, the flange of each rib being a relict margin”.

Peña Cantero et al. (1998: 299) considered Reticularia annulata Watson, 1973 actually to belong to the pterobranch hemichordate genus Rhabdopleura , but the authors gave no arguments supporting their conclusion. Filellum annulatum was subsequently recorded from Patagonia and redescribed in the dissertation of El Beshbeeshy (1991), including details and figure of the hydranth. El Beshbeeshy’s data undoubtedly refer to a hydroid and, most likely, to a species of Filellum . Whether the specimens assigned to F. annulatum by El Beshbeeshy are conspecific to the geographically distant material originally described by Watson is open to question.

Watson (2002) proposed the new hydroid genus Corystolona , assigned it to the family Clavidae , and mistakenly placed it in “Leptothecatae”. The holotype of the type species of Corystolona annulata ( Watson, 1973) is NMV G1922, as described by her in 1973. However, Watson (2002: 333) also collected “Abundant colonies of a hydroid previously described as Reticularia annulata Watson, 1973 ” and, based on this new material [(see Watson 2002: 334: “Description (of Tasmanian material)”], redescribed and provided illustrations (her Figure 1 ) of a specimen that is undoubtedly a member of “ Clavidae ” (today considered part of family Oceaniidae , see Schuchert 2009). The rationale of the redescription and new assignment was that “the small sample of Reticularia annulata from Pearson Island in the eastern Great Australian Bight had deeply withdrawn, partly decomposed, sterile hydranths and disposition of the specimen on the bryozoan host was such that the bases of the hydrocauli were obscured; the specimen was thus mistakenly referred to Reticularia Thomson, 1853 (junior synonym, Filellum Hincks, 1868 ). The smaller dimension of the type compared with those of the present specimens is almost certainly due [to] its being a young, infertile colony while the Tasmanian material ranges from young to aged” ( Watson 2002: 334). The dimensions of perisarc of the two specimens are obviously different, as well as their trophosomal morphology. Watson (2002) neither remarked about the reassignment of her species made by Peña Cantero et al. (1998) as a hemichordate, nor its subsequent redescription by El Beshbeeshy (1991).

We believe that the two papers by Watson describe different species; the 1973 one being a Filellum , and the 2002 one being a species of Anthoathecata and indeed a new species of Oceaniidae .

However, once Watson (2002) explicitly considered Corystolona annulata as linked to the holotype NMV G1922, both the species and generic name shall not be considered for nomenclatural purposes, because the holotype was intended to be a Filellum , not an oceaniid. Therefore, we consider F. annulatum a valid name based on the holotype material NMV G1922 (a microslide, and the remainder preserved material of the holotype colony NMV G2091). The Tasmanian material NMV F91280 (malinol mounted microslide, female colony, Port of Launceston, Tasmania, colonies from bryozoans on wharf pilings 1–4 m, Aquenal Pty Ltd, May, 2001, see Watson 2002: 334) undoubtedly represents a species of Corydendriinae (sensu Schuchert, 2004), and perhaps even the genus Corydendrium van Beneden, 1844, whose description was emended as “erect, branching or stolonal hydroid colonies […]” ( Schuchert, 2004: 335), therefore encompassing the diagnostic character “strictly stolonal colonies” ( Watson, 2002: 334) presented by Corystolona .

Figures

FIGURE 1. Filellum adhaerens (Nutting, 1901). (A) Hydrotheca, side view. (B) Hydrotheca, inclined and oral view. (C) Coppinia, side view. (D) Detail of the protective tubes. (E) Detail of the distal half of the gonotheca, including aperture. Scale bar: 200 µm (A); 150 µm (B); 300 µm (C, D, E).