Phylogeny, Biogeography, and Taxonomy

Abstract

The Order Solilugae is placed within the subphylum Chelicerata, class Arachnida (Phylum Arthropoda). The subphylum Chelicerata is typically divided into two classes: the Merostomata (aquatic forms, i.e. horseshoe crabs) and Arachnida (mostly terrestrial forms with the exception of a few species secondarily adapted to water). Chelicerates possess a pair of preoral appendages developed as 2-, 3-, or 4-jointed chelicerae or pincers (jaws), followed by a pair of appendages (pedipalps) that may be ambulatory in function or modified as accessory sensory structures or masticatory organs. The chelicerate body is divided into an anterior prosoma or cephalothorax (precheliceral metameres and segments I – IV), and a posterior opisthosoma (abdomen) (10 – 13 segments). Ancestrally, the chelicerates possess six pairs of prosomatic appendages (chelicerae, pedipalpi, and legs I – IV) and up to seven pairs of homologues of opisthosomatic appendages.