Taxonomic notes on the crab-spider genera Nyctimus Thorell, 1877 and Zametopina Simon, 1909 (Araneae, Thomisidae) with descriptions of six new species from Southeast Asia

The crab-spider genera Zametopina Simon, 1909 and Nyctimus Thorell, 1877 remain poorly studied, with significant gaps in their taxonomic understanding. Nyctimus has seen little study since its original description, and species assignments remain uncertain due to a lack of modern diagnostic data. By contrast, Zametopina, historically monotypic, was recently expanded with a second species (Z. wanliae Lin & Li, 2023) following a redescription of the type species, Z. calceata Simon, 1909.

Our study presents a review of these genera, primarily based on specimens collected from tropical Asia by the late Christa L. Deeleman-Reinhold as well as from the EFForTS project in the lowlands of Sumatra, Indonesia. The review includes the description of the following six new species: Nyctimus falcatus Benjamin & Dhiya’ulhaq, sp. nov. (♂), Nyctimus kinabaluensis Benjamin & Dhiya’ulhaq, sp. nov.

(♂ ♀), Nyctimus mutilloides Benjamin & Dhiya’ulhaq, sp. nov. (♂), Nyctimus quadripunctatus Dhiya’ulhaq & Benjamin, sp. nov. (♂ ♀), Nyctimus rendang Dhiya’ulhaq & Benjamin, sp. nov.

(♂ ♀), and Nyctimus saksang Dhiya’ulhaq & Benjamin, sp. nov. (♂). Nyctimus bistriatus Thorell, 1877 is redescribed and new locality records are provided.

Zametopina wanliae is recorded for the first time outside of Vietnam. Further, updated species descriptions of Nyctimus and Zametopina are provided, along with taxonomic clarifications of the genera. This study emphasises the fundamental importance of well-curated, historical collections and ongoing fieldwork in resolving the systematics of lesser-known arachnid lineages.