Melinnidae Chamberlin, 1919

Gunton, Laetitia M., Zhang, William, Kupriyanova, Elena K. & Hutchings, Pat A., 2023, New Species of Melinna (Melinnidae, Annelida) from the Australian Abyss with Comments on M. albicincta, M. cristata and M. elisabethae, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 125-154 : 127-130

Family Melinnidae Chamberlin, 1919

Melinninae Chamberlin, 1919: 443 . Emended Day, 1964: 103–107.

Melinnidae Stiller et al., 2020: 6 , figs 4, 5; Rouse et al., 2022: 238–241.

Diagnosis. Tubicolous. Hood like prostomium lying over the buccal region, with eye spots present or absent and nuchal organs present. Retractile buccal tentacles. Peristomium clearly demarcated from an achaetous segment. Typically, with 4 pairs of tapering conical branchiae (2–3 pairs in some species) on segments 2–5, although may appear to arise from segments 2 and 3. Neuropodia on segments 2–5 with acicular chaetae, from segment 6 neuropodia with pectinate uncini. Notopodia with capillary notochaetae from segment 4 or 5 and continuing with a variable number of thoracic segments (10–16). Variable number of abdominal segments (20–90) with only neuropodia. Often with a more or less distinct membrane across dorsum at level of segments 2–3. Postbranchial dorsal recurved hooks present or absent.

Remarks

The family Melinnidae was originally a subfamily within the family Ampharetidae Chamberlin, 1919 . Day (1964) emended the diagnosis of the subfamily and provided two tables listing the characters of genera and type species in the subfamily. As Day (1964) states, many new genera have been described since Chamberlin erected the subfamily. Day (1964) emended the diagnosis to include all members that have acicular neurochaetae on segments 2–5 (Day incorrectly numbers them as present on segments 3–6) and indicated that members of this subfamily may or may not have dorsal hooks and paleae are always absent. Later, as a result of a molecular and morphological study of the Terebelliformia, Stiller et al. (2020) elevated this subfamily to a full family, although they did not formally provide a diagnosis of the new family. Subsequently Rouse et al. (2022) provided a description of the family, including morphology, physiology, natural history and systematics, but no diagnosis.

The above family diagnosis is based on Stiller et al. (2020) and Rouse et al. (2022) although there are comments in Rouse et al. (2022) such as “some species show unusual neurochaetae on anterior segments”, thus it is unclear if these characters are restricted to particular genera or not. Furthermore, Rouse et al. (2022) clearly state that all Melinnidae have straight acicular spine­like neurochaetae on 2nd to 4th or 5th segments (chaetigers 1–4) which is contradictory to the previous statement. Similarly, Rouse et al. (2022) suggest that notopodia can begin on segment 4, although usually they begin on segments 5 or 6 and it is unclear if this is a generic character or not. Rouse et al. (2022) neither indicate the segments on which the dorsal hooks occur nor the genera in which they occur. According to Holthe (1986), these hooks are present on segments 3 and 4, but Rouse et al. (2022) do not agree with the segmental numbering system of Holthe (1986) who did not recognize the achaetous segment 1, thus all Holthe’s numbering is one number out. We suggest that all the genera in this newly erected family need to be rechecked to clarify the above characters, but this is beyond the scope of this paper.