An illustrated catalogue of South American species of Omorgus Erichson, 1847 (Coleoptera, Trogidae, Omorginae) including a neotype designation and taxonomical changes Author da Costa-Silva, Vinícius 0000-0002-4556-3793 Department of Zoology & Entomology, University of Pretoria, Private Bag X 20, Hatfield, 0028, South Africa & Laboratório de Scarabaeoidologia, Instituto de Biociências, Universidade Federal de Mato Grosso (UFMT), Cuiabá, Mato Grosso, Brazil Author Strümpher, Werner P. 0000-0002-7047-2666 Ditsong National Museum of Natural History, PO Box 413, Pretoria 0001, South Africa Author Barclay, Maxwell V. L. 0000-0003-4989-2014 Department of Life Sciences, Natural History Museum, London SW 7 5 BD, UK Author Vaz-de-Mello, Fernando Z. 0000-0001-9697-320X Laboratório de Scarabaeoidologia, Instituto de Biociências, Universidade Federal de Mato Grosso (UFMT), Cuiabá, Mato Grosso, Brazil text Contributions to Entomology 2024 2024-07-29 74 1 81 101 journal article 10.3897/contrib.entomol.74.e126799 339AB68C-DCB1-435F-B88E-2C42D0A7B05E Omorgus ( Haroldomorgus ) batesi ( Harold, 1872 ) Trox batesi Harold, 1872: 126 (original description); Arrow 1912: 54 (catalogue); Blackwelder 1944: 218 (catalogue); Vaurie 1962: 154 (redescription). Trox ( Omorgus ) batesi : Scholtz 1982: 8 (catalogue). Omorgus ( Haroldomorgus ) batesi : Scholtz 1986 a : 362 (phylogenetics); Scholtz 1990: 1418 (redescription); Zidek 2013: 7 (catalogue); Strümpher et al. 2014: 549 (systematics); Strümpher et al. 2016: 62 (systematics); Zidek 2017: 98 (catalogue); Hielkema and Hielkema 2019: 10 (checklist for the Guianas); Costa-Silva et al. 2021: 1997 (review of Brazilian species). Omorgus batesi : Deloya 2005: 122 (checklist). Type specimen examined. Holotype ( ♂ MNHN ). See Costa-Silva et al. (2021: 1997) for high-quality images of the type specimen. Type locality : “ Amazonestrom ” [ Amazonas River]. Geographic distribution. Argentina , Bolivia , Brazil and Paraguay ( Zidek 2017 ; Costa-Silva et al. 2021 ). Non-type examined material ( four specimens additionally to Scholtz (1990) and Costa-Silva et al. (2021) ). BRAZIL – Amazonas • 1; Parana da Eva ; 8 Nov. 1969 ; J. M. & B. A . Campbell leg.; CNC . – Mato Grosso • 1; Juina ; 1 Oct. 2022 ; K. R. Ferreira leg; CEMT • 1; Santa Cruz do Xingu , Faz. da Ilha ; 9 ° 45 ' 41 " S , 52 ° 15 ' 41 " W ; UV light trap ; 11–17 Jan. 2024 ; D. F. Rodrigues & T. I. Vitor-da-Silva leg.; CEMT . – Rio de Janeiro • 1 ♀ ; Magé , 70 km N [north] of Rio de Janeiro ; 15 Oct. – 10 Nov. 1999 ; W. Grosser leg.; NHMUK . Note. The monotypic subgenus Haroldomorgus Scholtz, 1986 a was established to accommodate Trox batesi Harold, 1872 , following a morphological phylogenetic analysis aimed at elucidating the suprageneric relationships within Trogidae (refer to Scholtz, 1986 a for details). One of the most distinctive features of Omorgus ( Haroldomorgus ) species is a complete absence of tubercles or ridges on the pronotum and elytra. Additionally, this species exhibits an oval-shaped scutellum that is not constricted at the base, which distinguishes it from the typical modern concept of Omorgus species. Following a morphological phylogenetic analysis conducted by some of the authors ( VCS , WPS, and FZVM – Costa-Silva et al. in press ), the genus Omorgus was recovered to be paraphyletic, restoring Haroldomorgus as a sister group to Omorgus + Polynoncus . In the first and only molecular phylogeny of Trogidae performed to date, by Strümpher et al. (2014) , no specimens of Omorgus ( Haroldomorgus ) batesi were used in the analysis. However, we have now obtained fresh specimens to revisit the molecular analysis and finally test the Scholtz’s (1986 a ) hypothesis and the position of Haroldomorgus within Trogidae .