Ticks (Ixodida: Argasidae, Ixodidae, Khimairidae, and Nuttalliellidae) of the world

The taxonomy of ticks (order Ixodida) has changed significantly over the past few decades. Many species have been described, synonymized, invalidated, or reinstated. The genus-level classification of ticks in the families Argasidae, Ixodidae, and Nuttalliellidae has also been revised. Here, we list 1033 tick species recognized as valid, including 21 fossil species. These ticks are grouped into four families: Argasidae (17 genera, 221 species), Ixodidae (20 genera, 800 species), Khimairidae (one genus, one species), and Nuttalliellidae (three genera, 11 species). An updated classification of tick genera is also provided.