Galathowenia Kirkegaard, 1959

Ibrahim, Nur Fazne, Villalobos-Guerrero, Tulio F. & Idris, Izwandy, 2024, Review of Oweniidae Rioja, 1917 (Annelida, Palaeoannelida) from Malaysia, with a description of two new species and a key to South China Sea species, Zoosystema 46 (20), pp. 513-542 : 516

Genus Galathowenia Kirkegaard, 1959

Galathowenia Kirkegaard, 1959: 67 .

DIAGNOSIS (adapted from Capa et al. 2012). — Cylindrical head, anteriorly truncated, terminal mouth extending mid-ventrally as an elongated slit and presence of ventral pharyngeal organ. Breakage groove between first and second chaetiger. Y-shaped oesophageal commissure. First three segments uniramous, with capillaries on notopodia. Following segments biramous, notopodia with capillary chaetae only and neuropodial uncini with two obliquely arranged teeth.

T YPE SPECIES. — Galathowenia africana Kirkegaard, 1959 , by original designation.

REMARKS

Galathowenia was established by Kirkegaard (1959) for G. africana , the holotype was collected during the “GALATHEA’’ expedition on the west coast of Africa. In addition to being differentiated based on the shape of the prostomium (anteriorly truncated) with a ventral cleft, G. africana species was characterised by having an “achaetous peristomium fused with the prostomium, the presence of two eye-spots and three thoracic segments without neuropodial hooks”. The validity of Galathowenia was later agreed upon by several taxonomists because of the shape of the prostomium ( Fauchald 1977; Kirkegaard 1983, 1996; Blake 1984, 2000; Imajima & Morita 1987; Parapar 2003b).

Currently, Galathowenia is featured by having a terminal mouth extending mid-ventrally as an elongated slit, the presence of a breakage groove between the first and the second segments, notopodia with only capillary chaetae on both uniramous and biramous segments, and uncini with a teeth of similar size and generally arranged obliquely ( Capa et al. 2012). Among all genera, Galathowenia is more similar to Myriochele because of the lack of distal appendages. However, they can also be distinguished by: 1) the truncated and elongated head of Galathowenia ; in contrast to the rounded head of Myriochele ; 2) the absence of acicular notochaetae in Galathowenia , which are present in Myriochele ; and 3) the presence of a breakage groove between segments 1 and 2 in Galathowenia , which is absent in Myriochele .

The species discrimination in Galathowenia is based on: 1) the presence/ absence of eyes on head structures; 2) the number, relative length, and distribution of the anterior uniramous thoracic chaetigers; 3) the relative length of the first biramous abdominal segment; 4) the position of the longest chaetiger; 5) the shape and dentition of the uncini; and 6) through the posterior end which bears a different number and structure of lobes.