Deltanthura, Shiraki & Shimomura & Kakui, 2022

Shiraki, Shoki, Shimomura, Michitaka & Kakui, Keiichi, 2022, A new neotenous genus and species, Deltanthura palpus gen. et sp. nov. (Isopoda, Anthuroidea, Paranthuridae) from Japan, with a revised key to the genera in Paranthuridae, Zoosystematics and Evolution 98 (1), pp. 109-115 : 109

Deltanthura gen. nov.

Diagnosis.

Eyes present. Pereonite 7 reduced and hidden laterally. Pleonites 1-5 fused but with sutures. Pleonite 6 entirely fused dorsally to telson; pleotelson triangular, without statocyst. Mandible acute, with 3-articulate palp. Maxilliped with 4-articulate palp; endite present. Pereopod 7 absent on non-manca individuals. Uropodal exopod elongate triangular, tapering.

Type species.

Deltanthura palpus Shiraki, Shimomura & Kakui, by original designation.

Etymology.

The generic name is a combination of the Greek letter delta (δέλτα), which is triangular in shape, referring to the shape of pleotelson, prefixed to anthura, from Greek anthos (a flower) and oura (a tail). The gender is feminine.

Remarks.

Like Pseudanthura and Paranthura , Deltanthura has an acute mandible with a 3-articulate palp, but it differs from the former two genera in having pereonite 7 reduced and in lacking pereopods 7. Deltanthura and four paranthurid genera share neotenous characters (reduced pereonite 7 and pereopods 7 lacking), but in Deltanthura the mandible is acute, with a 3-articulate palp and maxillipedal endites present, characters that are unique among the neotenous paranthurid genera (Table 1 ).

Deltanthura gen. nov. does not fit well within the clade ( Paranthura + neotenous clade) (cf. Poore 2001), as it has a maxillipedal endite. Rather, Deltanthura seems to be more closely related to Pseudanthura , as these two share multiple character states such as a triangular pleotelson; elongate triangular, tapering uropodal exopod; and maxillipedal endite. If this latter hypothesis is correct, the neotenous condition in Paranthuridae may not have had a single origin. In addition to the five neotenous genera now known in Paranthuridae , three neotenous genera are known in anthuroid isopods ( Poore 2009): the monotypic genera Exallanthura Kensley, 1980 and Leipanthura Poore, 2009 in Anthuridae Leach, 1814; and the genus Curassanthura Kensley, 1981 in Leptanthuridae Poore, 2001. We note that Poore (2009) pointed out that the Exallanthura females sensu Kensley (1980) may actually have been manca individuals.

The neotenous species Califanthura minuta Kensley & Heard, 1991 from the British West Indies may belong in Deltanthura gen. nov. It has the triangular pleotelson and tapering uropodal exopod ( Kensley and Heard 1991) that occur in Deltanthura but not in other Califanthura species. However, as the shape of mandible and the presence or absence of the maxillipedal endite (characters diagnostic for Deltanthura ) are unknown for C. minuta , we refrain from transferring it to Deltanthura .