A catalogue of the millipede species recorded or described from Chile is presented, both in continental and insular territories, including synonyms, type localities, and distribution maps, based on the published literature between 1847 and 2022. A total of six orders, eleven families, 26 genera, 75 species and two subspecies were found distributed almost all over the Chilean territory. Most of the records in Chile are concentrated in the central-south zone of the country; furthermore, the described species have a high degree of endemism and the existence of seven introduced species is recognized. A key for the identification of the orders, families, and genera of millipedes occurring in Chile are provided. Finally, the species Chondrodesmus auxus Chamberlin, 1957, Chondrodesmus sierricola Chamberlin, 1957 and Rhinocricus gaudichaudi (Gervais, 1847) are proposed in nomina dubia.

The millipede family Siphonorhinidae (order Siphonophorida) shows a scattered distribution in South Africa, Madagascar, India, Southeast Asia, and North America. So far, the family is unknown from South America, while species of Siphonophoridae, the second family of the order, are relatively abundant on the continent. However, not a single Siphonophorida is known from Chile. Here we describe the monotypic genus Notorhinusgen. nov. with N. floresisp. nov. and record a second Notorhinus (undescribed) species, as first records of the order Siphonophorida in Chile and of the family Siphonorhinidae in South America. Notorhinusgen. nov. is distinct from the remaining Siphonorhinidae by the arrangement of the sensilla basiconica on the antennae and other somatic and sexual characters. However, it shows close morphological affinities to the North American genus IllacmeCook and Loomis 1928. In the Americas Siphonorhinidae were previously only known from California (USA), where they inhabit subterranean micro-habitats. The Chilean species was found under a piece of decaying wood in a small patch of fragmented native forest. Thus, the group shows a disjunct antitropical distribution in America at ca. 37° North and 38° South. They might be the relict of a once greater distribution, which persisted in these areas due to similar climatic conditions.

The alien polydesmid millipede Oxidus gracilis is recorded from continental Chile based on new material revised. The distribution in the country was mapped by combination of records from new material collected, preserved specimens and observations from the Global Biodiversity Information Facility (GBIF).

Research on the diversity and biogeography of Chilean millipedes represents a significant gap in knowledge. To reduce this gap we conducted a study: (1) to investigate the current state of knowledge of millipede diversity, and (2) to assess the pattern and causes underlying the latitudinal diversity gradient in Chilean millipedes. In Chile, 95 native millipede species have been recorded. However, rarefaction and extrapolation curves showed that increased sampling effort will reveal more species. An asymptotic estimate of diversity predicted that millipede diversity fluctuates between 125 and 197 species. The estimate, though, was based on a limited data set. Therefore, millipede diversity is probably higher than predicted. Chilean millipedes were categorized as micro-range endemics because they all have latitudinal ranges of less than 1,000 km (with 78% of species exhibiting latitudinal ranges of only ~222 km). Millipede species richness also exhibited a bell-shaped latitudinal diversity gradient, i.e. diversity peaks in the temperate climate of central Chile and decreases towards the arid and polar climates of northern and southern Chile. A multiple regression analysis revealed that this biogeographic pattern is shaped by environmental variables related to water availability, ambient energy inputs and climatic stability. These environmental variables are proxies for two of the five biogeographic hypotheses we tested in this study, i.e. the water-energy balance hypothesis and climatic stability hypothesis. Both hypotheses suggest that millipedes need stable, humid and warm climates to grow, survive and reproduce (niche conservatism). These climatic conditions are only found in central Chile, which is consistent with the diversity peak observed in that region.

Research on the diversity and biogeography of Chilean millipedes (Diplopoda) represents a severe gap in knowledge. To reduce this gap we conducted a study to: (1) investigate the state of knowledge of millipede diversity, and (2) assess the pattern and causes underlying the latitudinal diversity gradient in Chilean millipedes. After combining the number of described species with those that have not yet been formally described, we concluded that there are 95 native millipede species in Chile. A diversity estimate suggested that in the future this number could increase to 125 or 197 species. However, this estimate is based on limited data. Therefore, the number of millipede species inhabiting Chile probably exceeds our estimate. Consistently, rarefaction-extrapolation curves revealed that we have not yet recorded a substantial fraction of millipede diversity and that increased sampling effort will reveal the presence of a greater number of millipede species in Chile. Most millipede species exhibited narrow geographic ranges in Chile. The north-south distribution of their species richness followed a bell-shaped latitudinal gradient of diversity, i.e. diversity peaked at the temperate climate of central Chile and then decreases towards the arid and polar climates of northern and southern Chile, respectively. The causes underlying this biogeographical pattern were water availability, ambient energy input and climate stability. This finding provided support for two of the five biogeographic hypotheses we tested: water-energy balance and climate stability. Thus, Chilean millipedes were more diverse at sites that exhibit warm and humid (temperate) climates for much of the year.