Aniptumnus Ng, 2002

Hari, P. Praved, Hershey, N. Regina & Mendoza, Jose Christopher E., 2022, On two species of Aniptumnus Ng, 2002 (Crustacea: Brachyura: Pilumnidae) from India, with a description of a new species from the coast of Kerala, Zootaxa 5214 (2), pp. 261-272 : 262

Aniptumnus Ng, 2002

Aniptumnus Ng 2002: 213 .— Ng & Clark 2008: 900, 901 (discussion).— Mendoza & Ng 2011: 59 (discussion).

Type species. Pilumnus (Parapilumnus) quadridentatus De Man, 1895 , by original designation.

Other included species. Aniptumnus bijoyi sp. nov., A. nefissurus ( Garth & Kim, 1983) , A. neolaevis ( Deb, 1995) comb. nov., and A. vietnamicus Ng & Clark, 2008 .

Diagnosis. Adult: Carapace transversely subhexagonal, broader than long; anterolateral margins divided into 4 teeth posterior to exorbital angle, first low, lobiform, second to fourth more projecting. Male thoracic sternum moderately broad, smooth; sternite 2 clearly separated from sternite 3 by transverse suture; small section of sternite 8 sometimes exposed when pleon locked onto thoracic sternum. Chelipeds distinctly unequal. Ambulatory legs without dactylo-propodal lock; posterodistal margin of P5 basis-ischium, with several large, closely packed spines or conical tubercles; posterior margin of P5 merus with spines and/or conical tubercles proximally. G1 sinuous, slender; G2 short, about one-fifth length of G1.

Zoea I: Rostral spine much shorter than antennal protopods; antennae extremely long, much longer than carapace; furcae of telson prominently elongate, inner margin armed with spines.

Remarks. Aniptumnus Ng, 2002 , has primarily been diagnosed by the condition of the fourth ambulatory leg (P5) where the basis-ischium has a comb-like postero-distal margin due to the peculiar placement of some spines or conical tubercles, and the posterior margin of the merus is armed with spines and/or conical tubercles proximally ( Ng 2002; Ng & Clark 2008). Subsequent to the establishment of the genus, Ng & Clark (2008) added two more species, A. nefissurus ( Garth & Kim 1983) and A. vietnamicus Ng & Clark, 2008 . Ghory et al. (2013) considered Pilumnopeus riui Takeda, 2001 , described from Hainan Island, China, as a junior synonym of A. quadridentatus . Trivedi et al. (2021) reported A. quadridentatus in the Indian Ocean (West Bengal, India) by virtue of their considering it to be a senior synonym of H. neolaevis Deb, 1985 . The identity of H. neolaevis is further discussed herein. Finally, Widyastuti & Rahayu (2022) recently reported a range extension for A. quadridentatus , with a new record from Timika, Papua, Indonesia.

It is important to note, however, that A. nefissurus is atypical in apparently lacking the comb-like posterodistal margin on the P5 basis-ischium, and both A. nefissurus and A. vietnamicus have the distal tip of their G1 tapering to a point (but with varying degrees of curvature), which is typical of many pilumnines, whereas in the type species and A. bijoyi sp. nov., the distal tip of the G1 has an apical lobe that is bluntly round and scoop-shaped. The position of A. nefissurus and A. vietnamicus in Aniptumnus will have to be evaluated further. Also, given that only A. quadridentatus has the first zoea morphology known, it will be critical to also determine the zoeal morphology of the other species of Aniptumnus as well.

The systematic position of Aniptumnus within Pilumnidae / Pilumninae is also an interesting issue to resolve. It is, thus far, the only pilumnid reported to have such long antennae on the first zoea, although another pilumnid genus, Leelumnus Mendoza & Ng, 2011 , also has a similar feature (Mendoza unpubl. data). In addition, both Aniptumnus and Leelumnus appear to favor estuarine areas and are a common component of fouling communities there ( Mendoza & Ng 2011). Another genus, Cryptopilumnus Hsueh, Huang & Ng, 2009 , has a similar granulation pattern on the P5 basis-ischium and merus, although it can be separated from Aniptumnus by the presence of a dactylo-propodal lock on the ambulatory legs, the complete fusion of thoracic sternites 1–3, and the predisposition to live in holes and crevices within rocks ( Hsueh et al. 2009), whereas Aniptumnus has no dactylo-propodal lock on the ambulatory legs, has fused thoracic sternites 1 and 2 but with sternite 3 separated from sternite 2 by a distinct suture, and it has not been recorded to live within rocks. Aniptumnus has also been compared to Latopilumnus Türkay & Schuhmacher, 1985 , primarily due to similarities in the general form of the carapace and pereopods, although in the case of Latopilumnus , the spines and conical tubercles on the P5 basis-ischium and merus are absent and the first zoea, which has short antennae, is typical of the family ( Ng & Clark 2008). These genera will have to be included in future phylogenetic studies concerning Aniptumnus .