Megalomma Johansson, 1925

Tovar-Hernández, María Ana & Carrera-Parra, Luis F., 2011, Megalomma Johansson, 1925 (Polychaeta: Sabellidae) from America and other world-wide localities, and phylogenetic relationships within the genus 2861, Zootaxa 2861 (1), pp. 1-71 : 14

GENUS Megalomma Johansson, 1925 amended

Branchiomma .— Claparède, 1869: 162, 163, junior homonym [non Kölliker, 1858]. Megalomma Johansson, 1925: 9–10 .— 1927: 130.— Perkins, 1984: 351–352.— Fitzhugh, 1989: 76.— Knight-Jones, 1997:

314.— Fitzhugh, 2003: 107.— Tovar-Hernández and Salazar-Vallejo, 2008: 1953–1954.— Giangrande and Licciano,

2008: 208.— Capa and Murray, 2009: 204–205. Type species: Branchiomma köllikeri Claparède, 1869 , a junior synonym of Sabella lanigera Grube, 1846 .

Diagnosis. Medium- to large-sized species with numerous radioles; radiolar skeleton with up to 30 cells; dorsalmost pair of radioles notably longer than the remainder radioles. Palmate membrane and radiolar flanges absent. Outer surface of radioles rounded or quadrangular. One or more pairs of radioles each with a single, sessile, compound eye situated along inner radiole margin near distal end. Dorsal lips triangular, radiolar appendages present, indicated by longitudinal ridge or “mid-rib” along entire length; distinct blood vessel and hyaline cartilage extending through length of appendages, without a branchial skeleton extension; dorsal pinnular appendages present or absent. Ventral lips and parallel lamella present. Caruncle, keel and ventral sacs can be present. Posterior peristomial ring collar present. Interramal eyespots can be present. Three shapes of inferior thoracic notochaetae arranged in two or more transverse rows: chaetae with distal end narrowing abruptly (Type A), those with progressively tapering distal tip (Type B) and those with the emergent shaft thick, short and with the distal margin rounded and hood with distal end surmounted by a mucronate tip (Type C). Two types of abdominal chaetae: narrowly hooded and broadly hooded. Thoracic uncini avicular; numerous, very small equal-sized teeth above the crest; breast well developed; handles of medium length. Assymetrical companion chaetae present: teardrop and/or sickle-shaped. Abdominal uncini similar to thoracic ones, but with shorter handles.

Remarks. Johansson (1925) recognized that Branchiomma köllikeri Claparède, 1869 , did not correspond to Branchiomma Kölliker, 1858 , and proposed Megalomma as a replacement name (nomen novum) for a junior homonym. Later, Johansson, in his monograph (1927) gave a diagnosis for Megalomma that he had named in 1925. Some authors have cited the author/year as Johansson, 1927, ( Hartman 1959; Perkins 1984; Fitzhugh 1989; Knight-Jones 1997; Tovar-Hernández & Salazar-Vallejo 2006; Giangrande & Licciano 2008); however, the new name was first published in 1925, and must be regarded as valid ( International Comission on Zoological Nomenclature 1999, Article 12.2.3).

Hartman (1959: 549) regarded Branchiomma köllikeri Claparède, 1869 , and Sabella lanigera Grube, 1846 , as a junior synonyms of Amphitrite vesiculosum Montagu, 1815 , and she incorrectly included the latter as type species for Megalomma (followed by Knight-Jones 1997 and Giangrande & Licciano 2008). However, as pointed out by Tovar-Hernández & Salazar-Vallejo (2008), the name of a type species remains unchanged even when it is a junior synonym or homonym, or a suppressed name, and the name of a type species should be cited by its original binomen ( International Comission on Zoological Nomenclature 1999, Article 67.1.2, Recommendation 67B). Consequently Amphitrite vesiculosum Montagu, 1815 , can no longer be considered the type species. Recently, Giangrande & Licciano (2008) based on examination of type material, confirmed the synonymy of S. lanigera , B. köllikeri and B. vesiculosum neapolitana Claparède, 1868 . Thus, based on the Principle of Priority of the ICZN (Article 23), the type species, B. köllikeri is the junior synonym of S. lanigera .

The present definition primarily follows Tovar-Hernández and Salazar-Vallejo (2008) with additions extracted from Capa and Murray (2009) and those derived from the present revision. These additions are the following: a radiolar skeleton composed up to 30 cells; outer surface of radioles can also be quadrangular; a keel and ventral sacs can be present ( Capa & Murray, 2009); there are three shapes of inferior thoracic notochaetae in Megalomma ; two types of abdominal chaetae and assymetrical companion chaetae teardrop and/or sickle-shaped (present study). See the previous section for description of these characters.