Anarthruridae Lang, 1971 sensu Larsen & Wilson 2002

Anarthruridae Lang, 1971 sensu Larsen & Wilson, 2002

Family Anarthruridae: Lang, 1971: 366 –367.

Family Anarthruridae: Sieg, 1978: 119 –121 (erection of Sub­family Anarthrurinae).

Family Anarthruridae: Holdich & Jones, 1983a: 88.

Family Anarthruridae (sensu Lang): Sieg, 1986b: 140

Family Anarthruridae: Sieg, 1986a: 17 (in part, includes families Agathotanaidae Lang, and Leptognathiidae Sieg (in part)).

Sub­family Anarthrurinae: Sieg, 1986a: 58–60 (in part, as Tribe Anarthrurini: 21,60).

Sub­family Anarthrurinae: Larsen & Wilson, 1998: 360, table 1.

Sub­family Anarthrurinae: Gutu & Sieg, 1999: 384.

Family Anarthruridae (restricted): Larsen & Wilson, 2002: 12.

Diagnosis (after Larsen & Wilson 2002). Female and preparatory male: medium body calcification. No plates in carapace; eyes absent. Pereonite 1 not reduced. Pleon with five free pleonites or all pleonites and telson fused, as wide as pereon. No articulated setae on pleonites. Antennule with four articles, antenna with six, article­3 without dorsal spiniform setae. Mandible molar process reduced or absent. Labrum with two lobes, median spiniform seta absent. Maxilliped bases partly fused; endites unfused, conical or subrectangular. Cheliped attachment through ventral pseudocoxa. Marsupium of four pairs of oostegites (female). Pereopods 1–3 with coxa; simple setae only on merus carpus and propodus. Pereopods 4–6 lack coxa; spiniform setae present. Pleopods present or absent. Uropod exopod fused to basal article; endopod with one or two articles. Male: with extensive sexual dimorphism, mouthparts reduced, pleopods longer.

Remarks. The family Anarthruridae has been twice redefined and expanded by Sieg (1983c, 1986a); in the latter, the genera belonging to the original family were placed in the subfamily Anarthrurinae, split into the tribes Anarthrurini and Agathotanaini. A more recent phylogenetic analysis (Larsen & Wilson 2002), using exemplar species, re­established the family and this is accepted here as the most valid classification. In this incarnation, the name has more or less reverted to its original meaning; the anarthrurid genera comprise Anarthrura and Allodaposia, possibly with Anarthruropsis, and Siphonolabrum. However, it is my opinion that Allodaposia is a Paranarthrura ­like agathotanaid and that the description was based on a juvenile male (with rudimentary pleopods) rather than a female. Hansen’s (1913) Leptognathia ‘group d’ species, i.e. L. latiremis, L. glacialis and L. profunda should also be placed here, as postulated by Lang (1971). The changes in classification and generic attribution within the Anarthruridae are summarised in Table 2.

Lang Sieg Sieg Larsen & Wilson Present

(1971) (1983) (1986) (2002) paper

Anarthrura G.O. Sars S.F. Anarthrurinae S.F. Anarthrurinae Allodaposia Anarthrura S.F. Akanthophoreinae Sieg

S.F. Leptognathiinae Sieg A narrow pleon is not a character of the group and this has led to anomalous and mistaken phylogenetic affinities to being drawn in the past. While that of A. simplex appears fused, it is dorsoventrally compressed and is actually as wide as the pereon. A narrow cylindrical pleon, lacking pleopods in females, is characteristic of agathotanaids but also occurs as a probable homoplasy in other genera such as Arthrura Kudinova­Pasternak, 1966 (= Libanius Lang, 1971). Similarly, fused uropod exopods are not diagnostic of anarthrurids and also occur, usually with a different appearance, in agathotanaids and tanaellids such as Araphura Bird & Holdich, 1984 and Arthrura.

Two groups of anarthrurids can be distinguished by labrum shape: one with a laterally compressed labrum (see Figs. 15 F–G), as in Siphonolabrum and Anarthruropsis, and the other with a ‘normal’ conical form (see Figs. 1 E–F), as in Anarthrura. A second, overlapping, group has a prominent fold on the outer surface of the cheliped propodus. Other characters with potential for use in phylogenetic analyses include: the number of long setae on maxilliped palp article­3 (three or four), the number of maxillule endite spiniform setae (four to eight), the presence or absence of mandibular molar processes, the incisor process crenulate or simple, broad or narrow (as in Siphonolabrum mirabile Lang, 1972, S. californiensis Dojiri & Sieg, 1997 and S. fastigiatum Sieg 1986 b), the presence or absence of ridges or folds on the chela, the number of setae of ventral margin of cheliped fixed finger (one or two), the presence or absence of complex spiniform setae on distal articles of pereopods 4–6, the number of said setae on carpus (three or four), the number of setae on each maxilliped endite (one or two), the presence or absence of setose margin of said endites, the distribution of setae on pleopods, and the number of terminal setae on uropod endopods.

Practical difficulties exist in determining some of these characters, especially in small species and when mouthparts such as mandibles are markedly reduced or weak; the last is the prevalent condition in anarthrurids. Equally, some of the existing descriptions of Anarthruropis and Siphonolabrum species are inadequate for revisionary work (i.e. A. longus Kudinova­Pasternak, 1984, A. langi Kudinova­Pasternak, 1976, A. similis Kudinova­Pasternak, 1990 and S. langi Kudinova­Pasternak, 1981).