Family Iphionidae Kinberg, 1856

Iphionea Kinberg, 1856: 383 (Iphione n. genus, I. ovata sp. nov., and I. muricata (Savigny in Lamarck, 1818); Kinberg 1858: 7.

Iphionidae: Baird 1865: 181 (Iphione, I. muricata, I. ovata and I. spinosa Kinberg, 1858); Norlinder et al. 2012 (phylogeny); McCowin & Rouse 2018: 95.

Iphioninae: Horst 1917b: 64; Pettibone 1986: 2 (revision); Hanley & Burke 1991: 38; Wehe 2006: 59 (Western Indian Ocean species).

Type genus: Iphione Kinberg, 1856.

Diagnosis (modified after Pettibone 1986: 5). Aphroditiforms with body short, oval to elongate, depressed, dorsally arched, with up to 39 segments. Prostomium with lateral antennae as anterior prostomial extensions, sometimes very short or missing; median antenna reduced to nuchal papilla, rarely well developed. Palps stout, smooth or with longitudinal rows of two types of papillae (larger conical to aristate, and shorter truncate). Two pairs of eyes, rarely missing. Facial tubercle dorsally visible between antennae. Tentacular segment reduced dorsally, often with a few capillaries. Segment 2 often with a nuchal lappet overlapping prostomium. Pharynx usually with nine pairs of marginal papillae and two pairs of jaws. Elytra large, stiff, with polygonal areas, 13–20 pairs, overlapped, covering dorsum, present in segments 2, 4, 5, 7, alternating in successive segments. Dorsal cirrophores often with large basal bulbous tubercles, styles slender, often subdistally swollen. Parapodia biramous; notopodia reduced with abundant notochaetae, plumose or spinous. Neurochaetae stout with subdistal series of minute transverse denticulations, delicate in first two neuropodia, larger in following ones, tips falcate, unidentate or bidentate, rarely hooded. Pygidium displaced dorsally, without anal cirri.

Remarks. Pettibone (1986: 5) attributed family authorship to Baird (1865). However, Wehe (2006) noted that Kinberg (1856) erected the family, as Iphionea. Iphionea is a noun in the nominative plural formed from the stem of an available generic name, Iphione (ICZN 1999, Arts 11.7.1.1, 29.1). It was used as a suprageneric taxon (Art. 11.7.1.2), and even though the initial suffix differs from currently used suffixes, it must be used with the original authorship and date, but with a corrected suffix (ICZN 1999, Art. 11.7.1.3, 32.5.3.1).

Composition. The family includes four genera: Iphione Kinberg, 1856; Iphionella M’Intosh, 1885; Iphionides Hartmann-Schröder, 1977; and Thermiphione Hartmann-Schröder, 1992; remarkably each apparently specializing on different marine environments. Iphione inhabits coral reefs and adjacent shallow, rocky or mixed bottoms in the tropical Indo-West Pacific to East Pacific and includes most species in the family; Iphionella lives at bathyal (520–914 m) depths; the monotypic Iphionides was discovered in anchihaline environments in Cuba; while the four species of Thermiphione have all been found at Pacific hydrothermal vents. Genera are separated by the presence of eyes, development of lateral antennae, number of pairs of elytra, presence of fimbriae, and presence or number of transverse rows of spinules in neurochaetae (Hartmann-Schröder 1992).

Iphionella McIntosh, 1885 was proposed for Iphione cimex de Quatrefages, 1866, described from the Malacca Strait, but with a specimen collected off the Philippines. Pettibone (1986: 23–25) studied McIntosh’s specimen and concluded that it was not conspecific with I. cimex of de Quatrefages, but belongs to a new species, which she then named Iphionella philippinensis Pettybone, 1986, based on McIntosh’s specimen. She also concluded that Iphione cimex de Quatrefages, 1866 belongs in a different genus, for which she proposed Gaudichaudius, and transferred it to the Harmothoinae (now Polynoinae, Polynoidae).