Paxtonia, Budaeva & Fauchald, 2011

Budaeva, Nataliya & Fauchald, Kristian, 2011, Phylogeny of the Diopatra generic complex with a revision of Paradiopatra Ehlres, 1887 (Polychaeta: Onuphidae), Zoological Journal of the Linnean Society 163 (2), pp. 319-436 : 410-411

PAXTONIA GEN. NOV.

Type species: Onuphis amoureuxi Intes & Le Loeuff, 1975 .

Gender: Feminine.

Diagnosis: Median antenna longer than lateral antennae; pseudocompound falcigers with moderately long and pointed hoods; limbate chaetae smooth, without serrations; anterior parapodia not enlarged; parapodia of roughly chaetigers 6–25 with large pockets, limited frontally by a fold of tissue; branchiae pectinate, present on all chaetigers except the few anteriormost ones; triangular to digitiform postchaetal lobes present on all chaetigers; one pair of anal cirri; maxillae VI present.

Remarks: Fauchald (1982) re-examined type specimens of Onuphis amoureuxi described by Intes & Le Loeuff (1975), and suggested that this species may represent a new genus, but did not describe it because of the low number of specimens available for examination. His conclusions were based on the presence of large parapodial pockets on anterior chaetigers and the position of chaetae in parapodia. Fauchald (1982) stated that the structure of parapodia of O. amoureuxi resembles that of Australonuphis Paxton, 1979 . Paxton (1986a) considered O. amoureuxi to be a member of Paradiopatra based on the presence of long hoods on anterior pseudocompound falcigers and the shape of maxillae I. She pointed out that parapodial pockets are common to several onuphid genera, such as Onuphis and Rhamphobrachium , and can’t serve as a diagnostic character for a new genus.

Here we tranfer O. amoureuxi to a new genus Paxtonia , based on the following observations. The presence of pseudocompound falcigers with long pointed hoods is not a unique character for Paradiopatra ; some species of Diopatra (e.g. D. angolensis and D. dubia ) have falcigers with long hoods. In addition, falcigers with long hoods are characteristic of Hyalospinifera ( Kucheruk, 1979c) . Consequently, long hoods on anterior falcigers cannot be used as a character of generic level.

The new genus has a long and thick median antenna, which is significantly longer than the lateral antennae. This condition never occurs in Paradiopatra ; furthermore, the majority of Paradiopatra species have relatively short median antennae. Paxtonia has distinct maxillae VI and only one pair of anal cirri, whereas Paradiopatra species always (except where the pygidium is unknown) have two pairs of anal cirri, and never have maxillae VI. Paxtonia differs from Paradiopatra in eight, rather than between two and four pairs of modified parapodia, well-developed postchaetal lobes on all chaetigers, rather than only on the anteriormost chaetigers 5–12, and branchiae continuing through the posterior region of the body, rather than being limited to the anteromedian parts of the body.

Etymology: Named in honour of the polychaete expert Hannelore Paxton, who has published a wide range of papers on the taxonomy and phylogeny of the Onuphidae , and has greatly increased our knowledge about this family.

Composition: One species.

Distribution: Eastern Atlantic Ocean, off West Africa, Gulf of Guinea; subtidal.