Phylogenomics illuminates the evolution of orb webs, respiratory systems and the biogeographic history of the world’s smallest orb-weaving spiders (Araneae, Araneoidea, Symphytognathoids)

[Display omitted] •Symphytognathoids and Anapidae are monophyletic consistent with the morphological hypothesis.•Multiple transoceanic dispersal events explain distribution of extant Anapidae.•Anterior tracheae transformed to book lungs and reductions multiple times.•Posterior tracheae were lost multiple times.•Orb web structure was lost four times and transformed to sheet web once. The miniature orb weaving spiders (symphytognathoids) are a group of small spiders (