Chondrodesmus riparius Carl, 1914, a millipede species new to the fauna of Costa Rica, originally described from Colombia, and introduced to and presently widespread across Europe (Diplopoda, Polydesmida, Chelodesmidae)

The fairly large-bodied Neotropical millipede genus Chondrodesmus Silvestri, 1897, includes 23 species described from Central America, to Costa Rica in the north, and 25 more from South America, to Colombia, Venezuela, Peru and centralwestern Amazonia of Brazil in the south. Among them, seven species have hitherto been described or recorded from Costa Rica, including Chondrodesmus hoffmanni (Peters, 1865), from an unknown place, and here revised based on the holotype.

Unexpectedly, it appears to differ markedly from all Costa Rican congeners, and instead it shows profound similarities to Chondrodesmus riparius Carl, 1914, from Colombia. The status of the European introduction heretofore provisionally referred to either as C. cf. riparius or C. riparius is confirmed here, since morphologically the European and Tropical American C. riparius populations represent the same species. To support this, comparative molecular studies using COI barcoding data, freshly obtained from a population from Costa Rica, with a European population of C. riparius show a congruence of 99.2%.

This not only indicates the conspecificity of C. riparius from South America and Europe, but it also suggests the source area whence its introduction to Europe could have occurred.