Axiidae Huxley, 1879

Poore, Gary C. B. & Collins, David J., 2009, Australian Axiidae (Crustacea: Decapoda: Axiidea), Memoirs of Museum Victoria 66 (2), pp. 221-287 : 222

Family Axiidae Huxley, 1879

Restricted synonymy.

Axiidae Huxley, 1879: 785 .— Sakai and de Saint Laurent, 1989: 4–5.— Poore, 1994: 96.

Calocarididae Ortmann, 1891: 47 .— Kensley, 1989: 960.— Poore, 1994: 98

Eiconaxiidae Sakai and Ohta, 2005: 69 .

Diagnosis. Carapace more or less laterally compressed, moderately to well calcified; cervical groove distinct at least dorsally; linea thalassinica absent; posterior margin of carapace with lateral lobes interacting with abdominal somite 1. Rostrum present, acute. Pleuron of abdominal somite 1 more or less produced. Eyestalks cylindrical. Antenna 1 with article 3 about as long as article 2. Antenna 2 with scale-like or well produced scaphocerite. Maxilla 2 scaphognathite with a posterior whip (rarely without). Pereopods 1 chelate, equal or unequal; pereopod 2 chelate; pereopod 3 simple; pereopod 4 simple or subchelate; pereopod 5 chelate. Pleopod l present or absent. Pleopod 2 similar in dimensions to pleopods 3–5, biramous; pleopods 3–5 endopodal rami elongated, not laterally expanded, with or without appendix interna. Uropodal rami lamellate, endopod more or less oval.

Remarks. Axiid lobsters are recognised by the combination of a prominent rostrum ending in an acute tip, similar laminar rami on pleopods 2–5, and oval uropodal endopod. They may be confused with Strahlaxiidae which have a rostrum with an apical notch and a triangular uropodal endopod. The family Calocarididae was revived and defined by Kensley (1989) and included in the key to thalassinidean families by Poore (1994). Poore’s key to genera included six genera and Poore (2008) listed two more. Kensley (1989) recognised the family on its being hermaphroditic, having unpigmented eyes and highly modified pleopod 2; in his view, axiids are gonochoristic (that is, the sexes are separate with gonopores on either coxae 3 [female] or coxae 5 [male] and pleopods 1 and 2 usually sexually dimorphic). In Kensley’s cladogram (1989: fig. 1) four calocaridid genera form a clade separated from a paraphyletic clade of three representative “axiid” genera. Tsang et al.’s (2008) molecular analysis of relationships between two calocaridid species ( Calastacus crosnieri and Paracalocaris sagamiensis ) and three axiids found the calocaridids were sister taxa and the axiids paraphyletic. Robles et al. (2009) used eight species in another molecular study and found that another calocarid, Calocaris caribbaeus , was embedded within the seven species of Axiidae . In their analysis the species labelled as belonging to the calocaridid genus, Calaxiopis, is here reidentified as an axiid, Pilbaraxius kariyarra sp. nov. Cladistic support for the family is currently weak in spite of its strong morphological unity. The problem lies more with the apparent paraphyly of Axiidae than with Calocarididae itself. Similarly, Sakai and Ohta (2005) isolated Eiconaxius in its own family, Eiconaxiidae , on the basis of rounded spinose dactyli on pereopods 3–5. This supposed unique feature defines the genus while nothing except its absence defines remaining axiids. However, this characteristic is shown in part in another genus (see discussion of Platyaxius below), weakening support for this family. We prefer to synonymise Calocarididae and Eiconaxiidae with Axiidae .

We note a structure hitherto unreported in many of the new species described below. Attached to the anterolateral margin of sternite 8, at the base of the socket of pereopod 5, is an articulating flap, oval-semicircular in shape with a setose margin (e.g. figs. 7d, e). In other species the structure is reduced to a setose ridge. Its homology is unclear but it appears to be a sternal scerite that may act as a valve at the posterior of the branchial cavity.