Lepidocharontidae Galassi & Bruce

Galassi, Diana M. P., Bruce, Niel L., Fiasca, Barbara & Dole-Olivier, Marie-Jose, 2016, A new family Lepidocharontidae with description of Lepidocharon gen. n., from the Great Barrier Reef, Australia, and redefinition of the Microparasellidae (Isopoda, Asellota), ZooKeys 594, pp. 11-50 : 12-15

Taxon classification Animalia Isopoda Lepidocharontidae

Lepidocharontidae Galassi & Bruce fam. n.

Diagnosis.

Male. Body dorsally flat, slender, ~4 –10× long as wide, without chromatophores; somites all subsimilar in width, somites sub-rectangular or trapezoidal, lateral margins of head and pereionites sub-parallel. Pleon of one segment, with free lateral margins. Head with weak or absent rostrum, without pseudorostrum. Eyes absent. Antennula with maximally 4 flagellar articles. Antenna flagellum longer than podomeres. Antennal scale (rudimentary exopod) present, even if more or less developed among genera. Mandible incisor with 2 to 8 cusps; molar process subconical, without grinding surface, with apical unequal smooth and pinnate setae; spine row and lacinia mobilis present, the latter only on left mandible. Maxilliped slender, covering entire mouthpart field, endite distal margin narrowly rounded; epipod slender, quadrate or distally acute; palp composed of 5 articles; 2 stiff pectinate setae always present on maxilliped distal article. Pereiopods 1-7 subsimilar, always without subchela; all pereiopods with 2 dactylar claws; pereiopods articulating dorso-laterally or laterally, and projecting ventrally (in Janinella and Microcharon ) or outwards (in Lepidocharon ). Penial processes with openings coalescent and medial. Male pleopods 1 and 2 not operculate; male pleopod 1 distally rounded or subtruncate, with or without acute distolateral lobes; proximal part of the pleopod with or without scale-like elements on postero-lateral margins; stylet-guiding grooves running parallel to the lateral free distal margin of pleopod 1 and folded by a hyaline lamella (transversal and unfolded in Janinella ); pleopod 3 endopod with 3 plumose setae (marine taxa) or without plumose setae (freshwater taxa), exopod slender. Pleopod 4 globular, pleopod 5 absent. Uropods biramous, ventrally inserted on pleotelson, protopod large, c. 0.5-1.3 as long as pleotelson; protopod length/width ratio c. 2.5-4.5; rami slender with exopod articulating anteriorly to endopod. Anus terminal, not covered by pleopods. Anus outside pleopodal chamber, between bases of uropodal protopods.

Female. Operculum (pleopod 2) from sub-quadrate (as long as wide) to more than 2 times longer than wide, with free distal margin deeply incised medially, faintly incised, or without medial incision, armed with 4 or 2 setae, or unarmed.

Genera included.

Microcharon Karaman, 1934; Janinella Albuquerque, Boulanouar & Coineau, 2014; Lepidocharon Galassi & Bruce, gen. n.

Genus incertae sedis.

Angeliera Chappuis & Delamare Deboutteville, 1952.

Remarks.

Wilson and Wägele (1994) and Wilson (1994) critically discussed the status of the Microparasellidae in relation to the Janiridae on a cladistic phylogenetic basis. Wilson and Wägele (1994) in their review of the Janiridae analysed the status of the family Microparasellidae in detail, reviewing the history of the debate over the status of the family. Wilson (1994) also included the Microparasellidae in his cladistic analysis of the phylogeny of the Janiridae . Wilson and Wägele (1994: page 721) stated "The family concept of the Microparasellidae may be open to challenge because Microparasellus is distinct from the other three genera in these autapomorphies", these being the differences in the somatic and uropodal morphology. These authors went on to say "the composition of this family will require further study." In Wilson’s (1994) analysis, there were no supporting apomorphies for the Microparasellidae as then constituted, but there were separate supporting apomorphies for the genus Microparasellus and the clade holding the remaining genera, strongly suggesting that potentially these were two monophyletic clades, albeit the Microparasellidae being monogeneric. The principle basis for this is that each group had unique and derived uropod morphology and substantial differences in body morphology.

The description of the new genus Lepidocharon Galassi & Bruce, gen. n. led to a re-appraisal of the taxonomic status of the Microparasellidae and its constituent genera. We conclude that the Microparasellidae is a mono-generic family supported by a prominent acute or narrowly rounded rostrum, the antennal flagellum shorter than podomeres, all somites with straight lateral margins that also have scales, an indisputable ventral position of the pereiopods, the unique uniramous and short uropods (see Appendix 1). The remaining genera are housed in the new family Lepidocharontidae fam. n., the diagnostic characters being the elongate body (up to 10 × as long as maximum width), a weak or absent rostrum, the antennal flagellum longer than podomeres, the pereionites rectangular or trapezoidal in dorsal view, with sub-parallel lateral margins, a lateral or dorso-lateral position of the pereiopods, a tendency to reduction of pereiopodal coxal plates, and the uropod with a large protopod with the exopod articulating anteriorly and separately to the endopod.

Within the family Lepidocharontidae there is great uniformity of the diagnostic characters among all the genera. The genus Angeliera has been placed incertae sedis in the Asellota on the basis of marked differences in several morphological features that set this genus far away the basic body plan observed in Lepidocharontidae .

The largest genus in the Lepidocharontidae is Microcharon with 77 species, both marine and freshwater. Many species lack full descriptions, and there are inconsistencies in the distribution of certain characters within the genus. A dorsal view of the head is not routinely figured; when figured, it can be seen that some species do have a rostral point or rostrum, while others have the anterior margin of the head weakly concave.

The generic name Microcharon is unavailable under the ICZN (1999) 's rules because the genus was established by Karaman (1934) without type species designation. This prevents the use of “Microcharontidae” (from the most speciose and well-known genus Microcharon ) as the family name because ICZN (1999) ' article 13.2 unambiguously states: "To be available, every new family-group name published after 1930 must satisfy the provisions of Article 13.1 and must be formed from an available genus-group name then used as valid by the author in the family-group taxon [Arts. 11.7.1.1, 29]". Therefore we here propose the name Lepidocharontidae fam. n.

The family name Microparasellidae was first introduced by Karaman (1934: page 44) when describing the genus Microcharon , although the family had been earlier diagnosed by Karaman (1933: page 17) with the accompanying statement " Microparasellus n. fam., n. gen.", but without type-species designation for the genus Microparasellus (see Karaman 1933). According to the ICZN (1999: Article 13.2) the family name Microparasellidae proposed by Karaman (1934) is thus a nomen nudum, because the family was erected on the unavailable generic name Microparasellus Karaman, 1933 that lacked type-species designation. Nevertheless, Article 13.2.1 states that "A family group name first published after 1930 and before 1961 which does not satisfy the provisions of Article 13.1 is available from its original publication only if it was used as valid before 2000, and also was not rejected by an author who, after 1960 and before 2000, expressly applied Article 13 of the then current editions of the Code". The family name was considered valid until 2000, and for this reason it is an available name as Microparasellidae Karaman, 1934. The family name Microparasellidae is then valid.

Conversely, we provisionally maintain current and common usage of the names Microparasellus and Microcharon , and this is discussed in more detail together with a new diagnosis for the Microparasellidae (see Appendix 1). As the nomenclature within the family Microparasellidae is well established and widely used, a proposition (Galassi and Bruce in preparation) will be submitted to the ICZN Commission for maintaining the stability of the current nomenclature and related authorities.

Key to Microparasellidae and genera of Lepidocharontidae fam. n.