Ophiuroid species names were collected from the literature and entered into the online World Ophiuroidea Database [1] , part of the World Register of Marine Species (WoRMS) [6] . The current taxonomic status of the about 3000 nominal species and over 4000 names (including new combinations) was assessed and recorded in the database. Then these data were used to assemble Table 1 , numbers of species and genera per family. The systematics largely follows Smith et al. [46] , except where more recent information is available. Ophiocanopidae was removed by Stöhr et al. [61] and its only genus Ophiocanops is included in Ophiomyxidae. The genera Ophiomoeris and Ophiochondrus , formerly placed in Hemieuryalidae, have recently been transferred to Ophiacanthidae [47] . The systematics of the Euryalida has been revised recently and the family Asteroschematidae has been lowered to subfamilial rank within Euryalidae [51] (link).
A biogeographic analysis of the world's extant ophiuroid species was performed by extracting a list of described species from the World Ophiuroidea Database [1] . Distributional data was obtained from a global database of museum catalogue sample data [62] (link), supplemented by additional records from the taxonomic literature to ensure a coverage of all species. We selected this database, because the World Ophiuroidea Database is complete with regard to taxonomic information, but still lacking in distributional data. Other possible databases that collect distribution data are the Encyclopedia of Life (EoL), the Global Biodiversity Information Facility (GBIF) and the Ocean Biogeographic Information System (OBIS), but none of these has yet sufficient amounts of data. The imprecise nature of the data contained in older taxonomic literature did not permit a quantitative approach to defining biogeographical regions. Instead, the world's marine environment was divided into 12 a priori large-scale regions based on available information (Figure 6 , see below) and four depth strata: shelf (0–200 m), bathyal (200–3500 m), abyssal (3500–6500 m) and hadal (below 6500 m) [63] . The aerial extent of these regions and depth strata was calculated from the ETOPO bathymetric dataset [64] . Equatorial regions were defined as being bounded by the 30° latitude in both hemispheres, the approximate boundary of tropical shallow-water coral-reef distributions [65] and the bathyal tropical-temperate transition in the Indo-Pacific [46] , [59] . Polar regions were bounded by 60° latitudes, thus separating the Antarctic continent from most of the subantarctic islands [66] . Temperate/boreal regions were defined as falling between these zones, 30–60° in each hemisphere. Longitudinal boundaries were set for the equatorial and southern temperate regions in mid-ocean reflecting the faunal relationship between offshore areas and nearby continental margins. The Indian Ocean boundary was set at 90°E, placing the Chagos and St Paul/Amsterdam islands in the Indian and South Africa regions respectively, and the Christmas/Cocos Islands and Indo-Malay archipelago in the Indo-Pacific region. The Atlantic regions were broadly separated by the Mid-Atlantic Ridge. The boundary in the Pacific Ocean was placed between the eastern Pacific islands of Juan Fernandez-Galapagos-Clipperton and the Indo-Pacific Hawaii-Pitcairn-Easter Islands. These regions reflect our knowledge of the fauna at shelf and upper bathyal depths, however, we have adopted the same regions for deeper areas to facilitate inter-depth comparisons. In reality, species ranges will not be exactly congruent and adjacent biogeographic regions or depth strata are likely to form broad transition zones, making it problematic to define precise biogeographical boundaries [62] (link). The temperate regions in particular contain enhanced species turnover between tropical, temperate and polar faunas [62] (link). The lack of quantitative location data from the older taxonomic literature also precludes the adjustment of regional species richness by sampling effort [67] . Despite these limitations, we believe that the data are useful for a first approximation of global ophiuroid biogeography.
A biogeographic analysis of the world's extant ophiuroid species was performed by extracting a list of described species from the World Ophiuroidea Database [1] . Distributional data was obtained from a global database of museum catalogue sample data [62] (link), supplemented by additional records from the taxonomic literature to ensure a coverage of all species. We selected this database, because the World Ophiuroidea Database is complete with regard to taxonomic information, but still lacking in distributional data. Other possible databases that collect distribution data are the Encyclopedia of Life (EoL), the Global Biodiversity Information Facility (GBIF) and the Ocean Biogeographic Information System (OBIS), but none of these has yet sufficient amounts of data. The imprecise nature of the data contained in older taxonomic literature did not permit a quantitative approach to defining biogeographical regions. Instead, the world's marine environment was divided into 12 a priori large-scale regions based on available information (
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