Eiconaxius Bate, 1888

Komai, Tomoyuki & Tsuchida, Shinji, 2012, Rediscovery and redescription of a sponge-associated axiid shrimp, Eiconaxius acutifrons Bate, 1888 (Crustacea: Decapoda: Axiidea), Zootaxa 3393, pp. 27-40 : 28

Eiconaxius Bate, 1888

Remarks. The classification of Eiconaxius is subject to disagreement. Sakai & Ohta (2005) established a monotypic family Eiconaxiidae mainly using typical generic characters of Eiconaxius . They claimed that the family “is conspicuously different from all other genera of the family Axiidae ”, citing the chelate second pereopod, rounded dactyli with accessory spinules on the third to fifth pereopods, indistinct cervical groove and absence of the male first pleopod. Tsang et al. (2008) performed a phylogenetic analysis of thalassinidean taxa using partial nuclear 18S, 28S rDNA and mitochondrial 16S rDNA sequences. Their analysis clearly suggests that Eiconaxius is subordinated in other genera of Axiidae . Poore & Collins (2009) argued that all but the shape of the dactyli of the third to fifth pereopods are commonly seen in other axiid genera. They concluded by placing Eiconaxiidae in the synonymy of Axiidae . Komai et al. (2010) followed Poore & Collins (2009). On the other hand, Sakai (2011) continues to recognize Eiconaxiidae , and proposed further a new family Eiconaxiopsididae for the newly established genus Eiconaxiopsis Sakai, 2011 to accommodate a new species E. heinrichi Sakai, 2011 (type species) and Axius (Eiconaxius) sibogae de Man, 1925.

The subspatulate, ovate dactyli of the third and fourth pereopods are diagnostic of all known species of Eiconaxius and Eiconaxiopsis sibogae , and thus this character could be apomorphic ( Poore 1994). As pointed out by Poore & Collins (2009), species of Platyaxius Sakai, 1994 have similar shaped dactylus on the fifth pereopod, suggesting a possible relationship between the two genera. On the other hand, Eiconaxiopsis heinrichi has normalshaped, claw-like dactyli of the third to fifth pereopods, like as in all other axiid taxa, and this plesiomorphic character clearly excludes Eiconaxiopsis heinrichi from Eiconaxius sensu lato. Nevertheless, Eiconaxiopsis sibogae is separated from other species of Eiconaxius only by the possession of a first pleopod in males, and this makes Eiconaxiopsis possibly a paraphyletic assemblage. Considering the present morphological comparison and the phylogenetic analysis by Tsang et al. (2008), there is no merit in recognizing Eiconaxiidae and Eiconaxiopsididae . Following Poore & Collins (2009), we propose to synonymize Eiconaxiidae and Eiconaxiopsidae under Axiidae .