TAXONOMIC ARTICLE Deviant unicorns: monocerate and dicerate versions of Carlotta Roewer, 1943 (Opiliones: Gonyleptidae), with description of four new species from Eastern Brazil Adriano Brilhante Kury 1 | Amanda Cruz Mendes 2 1 Departamento de Invertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil 2 Departamento de Zoologia, Instituto de Biologia Roberto de Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil Correspondence Adriano Brilhante Kury, Departamento de Invertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, S ˜ ao Crist ov ˜ ao, 20.940-040, Rio de Janeiro, RJ, Brazil. Email: adrianok@gmail.com Funding information Fundaç ˜ ao Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Grant/Award Numbers: E-26/211.859/2021, E- 26/210.297/2021, E-26/210.148/2019 (249116), E- 26/200.085/2019; Conselho Nacional de Desenvolvimento Científico e Tecnol ogico, Grant/Award Numbers: 430748/2018-3, 311531/2019-9 Abstract In this study, the understanding of the harvestman genus Carlotta Roewer, 1943, is expanded. Carlotta currently comprises two species found in central Espírito Santo state. The descriptions of the existing Carlotta species have been supplemented, including genital morphology. Four new species are herein described—Carlotta beckeri sp. nov., Carlotta bicornis sp. nov., Carlotta iohannis sp. nov. and Carlotta obtortrix sp. nov.—extending the range of the genus both southwards and north- wards from southern Espírito Santo to southern Bahia. Among the new findings, a unique trait is exhibited by two species: a pair of spines on the ocularium (dice- rate), in contrast to a single spine (monocerate). This variation is significant, as the number of spines on the ocularium plays a crucial role in the Roewerian diagnosis for the genus. The characterisation of the genital morphology of Carlotta species is refined, with the identification and naming of two distinctive structures: the dilo- phium—two parallel lamellate ridges along the disto-ventral surface of the stylus, terminating in a broader loop—and the skeletal flabellum—a framework of arched cylindrical tapering branches with multiple ramifications. By shedding light on these newly identified structures, a more comprehensive understanding of the diversity and evolutionary traits within the Gonyleptidae is contributed through this study. KEYWORDS Arachnida, Brazilian Atlantic Forest, Grassatores, harvestmen, Neotropics INTRODUCTION The harvestmen fauna of the Brazilian state of Espírito Santo is seriously undersampled—most species are recorded from the famous locality of Santa Teresa, but when incursions are made in other areas of the state, a wealth of undescribed species is revealed. The AracnoLab (Arachnology Section of the Museu Nacional, Universi- dade Federal do Rio de Janeiro, Rio de Janeiro, Brazil) has conducted several expeditions to Espírito Santo and adja- cent southern Bahia, yielding specimens that may be assigned to the gonyleptid genus Carlotta Roewer, 1943 (Figures 1 and 2). The genus Carlotta, as currently understood, is known from two species. In this paper, we redescribe the type species of the genus, Carlotta serratipes Roewer, 1943 (Figure 1f), and Carlotta dubia (Soares, 1944) (Figure 1e). Additionally, we describe four new species from Eastern Brazil (localities in Bahia and Espírito Santo states). Diverg- ing from the diagnostic hallmark of a single spine on the ocularium, two of the newly described species exhibit a distinctive pair of spines atop the ocularium, which by the traditional Roewerian system (Henriksen 1932: 222), would assign them to a different genus. We also provide an identification key for the species of Carlotta and a map with the distribution of its species. Adriano Brilhante Kury: https://www.zoobank.org/urn:lsid:zoobank.org:author:60FAE1F8-87F7-4A5F-BE78-BEB25BC4F898 Amanda Cruz Mendes: https://www.zoobank.org/urn:lsid:zoobank.org:author:086CA672-976C-4884-8739-1D3E06131135 This paper: https://www.zoobank.org/urn:lsid:zoobank.org:pub:AA37833E-21FF-4D80-80C5-3BD832F342C2 Version of record published on 29 May 2024 Received: 24 August 2023 Revised: 17 December 2023 Accepted: 28 January 2024 DOI: 10.1111/aen.12683 Austral Entomology. 2024;63:175–209. wileyonlinelibrary.com/journal/aen © 2024 Australian Entomological Society. 175