Dineutus Macleay 1825
Creators: name: Gustafson, Grey T
name: Miller, Kelly B
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Gyrinidae
Dineutus

description: GENUS DINEUTUS MACLEAY, 1825
(FIGS 1, 4C, 5E, 6D, 7A–D, 8C, 9E, 9G, 11B–D, 13D)
Dineutus Macleay, 1825: 30, type species Dineutus politus Macleay, 1825.
S y n o n y m s: N e c t i c u s L a p o r t e, 1 8 3 5, D i n e u t e s Régimbart, 1882a.
Diagnosis: The genus Dineutus can be diagnosed within the Dineutini by the following combination of characters: (1) Gular suture complete, (2) frons without lateral bead (Fig. 4C), (3) antennal flagellum with 6–7 flagellomeres (Fig. 5E), (4) pronotal transverse impressed line present, (5) scutellar shield invisible with elytra closed, (6) protibia and male protarsi narrow (Fig. 9E), (7) mesotarsal claws sexually dimorphic, (8) metaventrite medially triangular in shape (Fig. 6D) and narrow and (9) female RT with vaginal shield (Fig. 11B–D) (Brinck, 1980, 1983, 1984). The genus Dineutus lacks a single distinct autapomorphy among gyrinid genera. A character that comes close is sexually dimorphic mesotarsal claws, but this character is a synapomorphy shared with Porrorhynchus (and potentially Mesodineutes Fig. S9); however, the sexual dimorphism is most pronounced among species of Dineutus. The other synapomorphies with Porrorhynchus include the invisible scutellar shield and most noticeably the female RT possessing a vaginal shield. Dineutus can be readily distinguished from all other dineutine genera by the narrowed protibia, which is likely the sole apomorphy separating this genus from Porrorhynchus. Dineutus can be furthered distinguished from Porrorhynchus in having a complete gular suture and the pronotal transverse impressed line present.
Taxonomy: The genus was monotypic when originally erected by Macleay (1825). Régimbart subsequently treated the genus several times, revising it and adding many species (Régimbart, 1882a, 1886, 1892, 1907). Hatch (1926) was the first author to divide the genus into subgenera, based primarily on overall body shape. Georg Ochs (1926, 1955) subsequently erected numerous subgenera, including subsuming Porrorhynchus as one of the subgenera. Since Ochs’ work, no new subgenera have been proposed, but the composition of the subgenera has been re-arranged by Guignot (1950), and most recently by Brinck (1955b), who attempted to provide distinct morphological traits identifying each subgenus, unsuccessfully.
There are currently 92 species within the genus Dineutus, making it easily the largest genus within the Dineutini.
Distribution: Dineutus has a near global distribution, missing from Europe, and most notably from South America (Fig. 14D) (Mouchamps, 1949b; Brinck, 1955b, 1976; Satô, 1962; Mazzoldi, 1995; Watts & Hamon, 2010; Hájek & Reiter, 2014; Gustafson & Miller, 2015; Lee & Ahn, 2015). Currently, the highest diversity is in the Austral region, primarily in New Guinea, but this likely reflects bias due to recent taxonomic work on species in this region (i.e. Brinck, 1976, 1981, 1983, 1984). The second highest diversity is found in tropical Africa.
Discussion: This is the largest and most widely distributed genus within the Dineutini.
description: Published as part of Gustafson, Grey T & Miller, Kelly B, 2017, Systematics and evolution of the whirligig beetle tribe Dineutini (Coleoptera: Gyrinidae: Gyrininae), pp. 118-150 in Zoological Journal of the Linnean Society 181 (1) on pages 129-131, DOI: 10.1093/zoolinnean/zlw014, http://zenodo.org/record/14805073