Matthewsianus Kirejtshuk, 2022

Kirejtshuk, Alexander G. & Kovalev, Alexey V., 2022, Monograph on the Cillaeinae (Coleoptera: Nitidulidae) from the Australian Region with comments on the taxonomy of the subfamily, Zootaxa 5103 (1), pp. 1-133 : 106-107

42. Genus Matthewsianus Kirejtshuk et Kovalev, gen. nov.

LSID urn:lsid:zoobank.org:act:E532AC27-8F7A-401F-90B4-99A7C5F7C68D

Type species: Brachypeplus olliffi Blackburn, 1902 .

Diagnosis. This new genus is characterized by the comparatively subparallel-sided or slightly oval body, subflattened and partly subconcave dorsally, and somewhat convex ventrally; pronotal and elytral sides clearly explanate, and also densely and shortly ciliate; dorsum densely and shortly pubescent; underside with more sparse and longer hairs; strongly flattened dorsal surface and elytra even medially concave; head with moderately small eyes located at midlength, labrum divided by median suture, distinctly outlined antennal grooves rather short, S-shaped and convergent; pronotum with trapezium-likely excised anterior edge and posterior angles slightly projecting posteriorly; comparatively short elytra (about even shorter than combined width); abdominal laterosternites V and VI rather emarginate along inner side at base and widened posteriorly; comparatively widely separated all pairs of coxae; procoxae clearly closed posteriorly; posterior edge of metaventrite between coxae shallowly arcuately emarginate; tibiae usually subtriangular or arcuately dilated along outer edge; tarsi moderately widely lobed; tarsal claws narrow and simple.

Comparison. Matthewsianus gen. nov. is easily diagnosed after the above key to genera and subgenera of Australia and it is very distinct from all genera of the subfamily in the medially shallowly concave elytra. It shares the most similarity with very diverse genus Brachypeplus and Leiopeplus , differing from them also in the diffuse elytral punctation and prosternal process rather short and comparatively wide between procoxae, and also from the second in the clear dense ciliation along sides of pronotum and elytra. Besides, this new genus differs from both in the pronotum with the clear rapezium-shaped excision at its anterior edge. From the inquilinous genus Onicotis occuring in Australia, Mattsewsianus gen. nov. differs in the less oval body outline, rather convex underside, much shorter cilia along sides of pronotum and elytra, nearly straight posterior edge and more narrowly explanate sides of pronotum and elytra, elytra without traces of both clear striae and deepened longitudinal rows of punctures, arcuately convergent antennal grooves, widely separated coxae in all pairs ( Onicotis has coxae very narrowly separated) and usual shape of antennal scape.

Etymology. The name of this genus is formed from the name of the outstanding Australian coleopterist, Eric G. Matthews, passed away in 2022, former curator of beetle collection in the South Australian Museum (Adelaide), who friendly and generously provided many colleagues with information on the Australian fauna and made a lot in assistance of study of specimens deposited in collection of this museums; masculine gender.

Composition. The new genus includes the type species with one junior synonym Brachypeplus insignis Lea, 1925 and also one new species here described.

Description. Body comparatively medium-sized (4.0- 6.7 mm) moderately elongate oval, subflattened dorsally with shallowly concave places in middle of elytra or also on head and pronotum, moderately to rather convex ventrally. Dorsum finely transversely rugulose with some small and sparse tubercles on pronotum, head and elytra or rather finely and densely punctured, finely microreticulate; elytra at most with very slight trace of striae; underside finely and densely punctured; body very shortly pubescent and with very dense cilia along pronotal and elytral sides.

Head subflattened, rather strongly narrowed only at base, eyes located before midlength, slightly depressed between antennal insertions and with anterior edge of frons truncate; S-shaped antennal grooves strongly convergent posteriorly and with distinct inner and outer edge; mentum extremely wide, arcuate at side, with anterior angles rather projecting anteriorly; pregenal process at hypostomal sinus moderately wide and arcuately curved. Ultimate labial palpomere subcylindrical and about 2.0 × as long as thick; ultimate maxillary palpomere subcylindrical and rather long. 11-segmented antennae bearing compact 3-segmented club without any evident trace of sexual dimorphism.

Pronotum at most slightly narrowing posteriorly and anteriorly, subflattened at disk and/or slightly sloping at distingly bordered sides, its anterior and posterior angles more or less projecting and with narrowly rounded tip; its anterior edge trapezium-likely emarginate and posterior one nearly straight to weakly emarginate at posterior angles. Elytra with widely rounded to subtruncate apices remaining last three abdominal segments uncovered, with narrowly explanate at bordered sides. Laterosternites of two preterminal abdominal segments moderately wide and widened posteriorly. Pygidium slightly medially convex or subconcave at sides and widely rounded to subtruncate in both sexes.

Prosternal process flattened, not curved along procoxae and somewhat widened at subtruncate apex. All pairs of coxae moderately separated. Mesoventrite medially flattened, at sides with distinct depressions for receipt of mesofemora. Metaventrite with distinct median line. Hypopygidium very widely rounded to subtruncate at apex in both sexes.

Legs moderately long and wide. Protibiae very narrow or rather arcuately widened along outer edge; two borders along meso-and metatibiae bearing dense and short setae; spurs rather short and stout. Tarsi with moderately to rather widely lobed tarsomeres 1-3 and claws simple.

Male anal sclerite rather long and with subacute apex.Aedeagus heavily sclerotized, moderately long, with blunt apex of penis trunk and with widely rounded to truncate apex of tegmen. Ovipositor of usual generalized structure and moderately sclerotized, inner and outer lobes gonocoxites well isolated, short styli located subapically.

Distribution. This genus is known only from Australia (WA, SA and QLD).