Pycnomerus vavitu, Porch & Smith & Greig, 2020

Porch, Nick, Smith, Tessa R. & Greig, Kelly, 2020, Five new Pycnomerus Erichson (Coleoptera: Zopheridae: Pycnomerini) from Raivavae, French Polynesia, Zootaxa 4718 (2), pp. 239-250 : 247-248

Pycnomerus vavitu sp. nov. Porch & Greig

( Fig. 1 , 4 )

Type Locality: Raʹirua Swamp, 0.8 km E. of Raʹirua, at 23°52.115’S 147°40.718’W.

Type Material. Holotype: French Polynesia, Austral archipelago, Raivavae, Raʹirua Swamp, DA 4 2008 core, 170–175 cm depth—1 prothorax, dorsally and ventrally complete except appendages. BPBM, Honolulu.

Paratype: French Polynesia, Austral archipelago, Raivavae, Raʹirua Swamp, 2016 cores, 150–200 cm—1 frag- mentary prothorax, approximately 2/3 complete. (Porch research collection) .

Diagnosis. Pycnomerus vavitu can be distinguished from P. prebblei Porch & Smith by its distribution, the more strongly dentate posterior angles of the prothorax, and its angular arcuate prothorax base in contrast to the more rounded base of P. prebblei Porch & Smith. It can be distinguished from the other Raivavae taxa by its almost square shape moderately parallel lateral margins, wide frontal angles, rounded basal angles, relatively flat pronotal disk and small, widely separated punctures.

Description. Based on holotype and single incomplete paratype.

Colour: Black.

Prothorax a little longer than wide, the greatest width at about 1/5/–1/4 of pronotal length. Lateral margins simple to very weakly crenulate, arcuate behind anterior angle to widest point, then straight and weakly converging to posterior angles. Lateral marginal sulcus very narrow adjacent to very narrow, raised border. Anterior angles obtuse angulate and weakly produced at sinuation of anterior marginal border. Anterior margin very weakly emarginate, a light sinuation to anterior angles, unbordered until joined to the lateral margins. Posterior angles strongly rounded, interrupted by several well-developed denticles. Posterior margin arcuate to angular at middle, and completely margined by sulcus. A pair of narrow, shallow, fovea in basal sulcus at approximately 1/4 basal width from posterior angles. Basal border narrow, not obviously punctate. Pronotal disk flat over medial third, a little declivous to anterior margin, and strongly declivous to lateral margins and anterior and posterior angles. Disk lacking medial impressions and bearing relatively evenly sized and evenly distributed punctures except behind middle where puncture density is reduced. Punctures small, elongate oval, separated by 1–5 times their length, becoming larger and closer laterally. Pronotal disk between punctures moderately shining with hints of elongate microsculpture laterally.

Prosternum (based on holotype only) moderately punctate with punctures mostly separated by several times their length, closer on prosternal process. Punctures mostly transversely ovate in middle of prosternum, becoming more circular posteriorly and laterally, bearing short very pale yellow setae. Anterior edge with weakly sulcate margin that extends only across middle third, with a distinct row of small punctures along front. Apex of prosternal process very weakly angularly emarginate.

Physical dimensions and Ratios

Pronotum measurements based on 2 types (some measurements not possible for paratype). Measurements of holotype in parentheses. Pronotum length: (0.77 mm)– 0.81 mm. Pronotum width: (0.74 mm)– 0.78 mm. Anterior width of pronotum: (0.60 mm). Medial width of pronotum: (0.72 mm). Base of pronotum: 0.66 mm–(0.67 mm). Lateral length of pronotum: (0.72 mm). Length/Width ratio: 1.04 (both).

Prosternum measurements (based on holotype only). Prosternum length: 0.56 mm. Length prosternum in front of coxae: 0.33 mm. Anterior foramen (estimated): 0.52 mm. Basal foramen: 0.48 mm. Prosternal process intercoxal width: 0.18 mm. Maximum prosternal process width: 0.32 mm. Ratio of Prosternal length/Length in front of coxae: 1.70.

Distribution. Known only from Raʹirua swamp, Raivavae, and likely to be a Raivavae endemic. Potentially ex- tinct: material known from other Austral Archipelago islands (Tubuai, Raivavae and Rapa) and nearby Cook Islands (Mangaia and Atiu) represent different taxa.

Etymology. Named for an alternative Polynesian name for Raivavae.

Comments. This species is very similar to the recently described P. prebblei Porch & Smith from Rimatara ( Porch & Smith 2017) and an undescribed species from Tubuai (Greig & Porch, unpubl. data). Initially, we considered including this material in a single variable species under the name P. prebblei Porch & Smith. As such, it would have been the only species, of the approximately 25 species of Pycnomerus so far recognised from the Australs, that occurred on more than one island. Although it is difficult to assess phylogenetic relationships based on morphology alone, we believe this material likely represents three closely related, but distinct species. More material, especially living specimens, if they could be discovered, would help resolve the nature of the relationships of this group of species with greater certainty.

Figures

FIGURE 1. Holotypes. Pycnomerus raivavae articulated prothorax and head, dorsal (top) and ventral (bottom)—(French Polynesia, Austral archipelago, Raivavae, Raʹirua swamp, RAI16-2 2016 cores, 150–200 cm depth). Pycnomerus rairua prothorax, dorsal (top) and ventral (bottom)—(French Polynesia, Austral archipelago, Raivavae, Raʹirua swamp, DA4 cores, 180–185 cm depth). Pycnomerus vavitu prothorax, dorsal (top) and ventral (bottom)—(French Polynesia, Austral archipelago, Raivavae, Raʹirua Swamp, DA4 2008 core, 170–175 cm depth). Pycnomerus mahanatoa prothorax, dorsal (top) and ventral (bottom)—(French Polynesia, Austral archipelago, Raivavae, Raʹirua Swamp, DA4 2008 core, 205–210 cm depth). Pycnomerus taralewisae prothorax, dorsal (top) and ventral (bottom)—(French Polynesia, Austral archipelago, Raivavae, Raʹirua swamp, DA4 cores, 245–250 cm depth). Scale bars = 0.5 mm

FIGURE 4. Dorsal and ventral views of prothoraces of P. vavitu and P. taralewisae. Holotypes indicated (with ‘HT’). Scale bar = 0.5 mm.