Dactylosternum grouvellei Guillebeau 1894, comb. nov.
Creators: name: Fikáček, Martin
name: Gimmel, Matthew L.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydrophilidae
Dactylosternum
Dactylosternum grouvellei

description: Dactylosternum grouvellei (Guillebeau, 1894), comb. nov.
(Figs 1–2)
Sternosternus grouvellei Guillebeau, 1894: ccvii.— Type locality: Indonesia: Sumatra.
Dactylosternum seriatum Knisch, 1921: 77 (Syn. nov.)— Type localities: Indonesia: Sumatra: Padang; Indonesia: Mentawei Islands: Pulau Sipura Is. (‘Sipora Sereinu’); Indonesia: Mentawei Islands: Pulau Sipura Is., Sioban (‘Si Oban’).
Type material examined. Sternosternus grouvellei: Holotype: 1 female (MNHN), located in the first of two boxes with outside label ‘Phalacrides / Typ. Guilleb.’, specimen with labels: ‘ Sumatra // Plaque intermediaire / large, posteriaux / éntroit parallel // Stenosternus [sic!] / Grouvellei // HOLOTYPE / STERNOSTERNUS / grouvellei / Guillebeau, 1894 / label attached by Fikáček, 2016’. Body length: 2.9 mm.
Dactylosternum seriatum: Syntype: 1 female (IRSNB): ‘Mentawei / Si Oban IV-VIII / Modigliani 94 // coll. A. d’Orchymont // A. d’Orchymont det. 1922 / Dactylosternum / seriatum Knisch’. Body length: 3.1 mm.
Additional material examined. INDONESIA: Sumatra: 1 male, 2 females, 1 spec. (IRSNB): ‘ Fort de Kock / (Sumatra) 920 M. / 1925 / leg. E. Jacobson // A. d’Orchymont det. 1929 / Dactylosternum / seriatum Knisch’. Illustrated aedeagus (Fig. 1 G) belongs to the single male from this series.
Comments on synonymy. The Dactylosternum subquadratum species group was established by Balfour-Browne (1942), but it was not defined by means of shared characters. It includes small-bodied species of Dactylosternum from the Oriental, Australian and Pacific regions, some of which are unique among the Coelostomatini in their punctation of the pronotum, frons and clypeus consisting of “scar-like” punctures (as in Fig. 2 A–B). Sternosternus grouvellei bears this unique type of pronotal and head punctation, which strongly supports its inclusion in the D. subquadratum species group sensu Balfour-Browne (1942).
Ten species were attributed to the species group by Balfour-Browne (1942): D. bakeri Orchymont, 1925 (peninsular Malaysia), D. bryanti Orchymont, 1925 (Sarawak), D. corbetti Balfour-Browne, 1942 (southern China, Philippines, peninsular Malaysia), D. densepunctatum Orchymont, 1937 (peninsular Malaysia), D. dohertyi Balfour-Browne, 1942 (Thailand, Malay Archipelago), D. leveri Balfour-Browne, 1942 (Fiji), D. papuense Balfour-Browne, 1942 (New Guinea), D. seriatum Knisch, 1921 (Malay Archipelago), D. subquadratum (Fairmaire, 1849) (Maluku, New Guinea, Pacific islands, Australia), and D. waigeuense Balfour-Browne, 1942 (New Guinea). Of these species, D. bryanti, D. densepunctatum, D. dohertyi and D. leveri do not have the typical scar-like pronotal and head punctures.
The remaining six species bear the scar-like punctures on the head and pronotum, but only D. seriatum corresponds with Sternosternus grouvellei in other characters of external morphology, including the extremely weak development of scar-like punctures on the elytra (Fig. 2 C, scar-like punctures are very distinct on the elytral intervals in all species but D. seriatum), small body size (2.9–3.3 mm in D. seriatum, 3.0– 3.8 mm in D. bakeri, D. corbetti and D. subquadratum, but 4.2–4.8 mm in D. papuense and D. waigeuense), and weakly convex body in lateral view (moderately convex in D. subquadratum and D. corbetti, highly convex in D. papuense and D. waigeuense). The holotype of Sternosternus grouvellei corresponds with the examined syntype of Dactylosternum seriatum also in the size and density of punctation of the head (Fig. 2 A), pronotum (Fig. 2 B) and elytra (Fig. 2 C), the size of the punctures of the elytral striae (Fig. 1A–B), the shape of the mentum (Fig. 2 D, F), meso-metaventral keel (Fig. 2 H–I) and the enlarged metafemora with transverse microsculpture (Figs 1C, 2 K–L). Moreover, the known distribution of Sternosternus grouvellei (i.e. Sumatra) corresponds to the known distribution of D. seriatum which does not seem to overlap with ranges of other species of the D. subquadratum group based on Orchymont (1926) and Balfour-Browne (1942), who both concluded that D. seriatum appears to replace D. subquadratum in Sumatra, Java, Engano and Mentawei (records of D. seriatum from continental SE Asia by Orchymont (1928) seem doubtful and need confirmation according to Balfour-Browne 1942).
For the reasons given above we consider Sternosternus grouvellei cospecific with Dactylosternum seriatum. Sternosternus grouvellei Guillebeau, 1894 is transferred to Dactylosternum, and becomes (as D. grouvellei comb. nov.) the senior synonym of D. seriatum Knisch, 1921 which is newly synonymized with it.
description: Published as part of Fikáček, Martin & Gimmel, Matthew L., 2017, On the identity of Sternosternus grouvellei Guillebeau, 1894 (Coleoptera: Hydrophilidae, Phalacridae), pp. 578-582 in Zootaxa 4237 (3) on pages 579-580, DOI: 10.11646/zootaxa.4237.3.9, http://zenodo.org/record/344771