A family tree, not a ladder.

Shared ancestry

An evolutionary tree describes branching lineages. Two groups are more closely related when their most recent shared ancestor is more recent. Similar lifestyles alone do not establish relationship: capture structures can change, disappear or develop in different contexts. Researchers therefore compare multiple characters and, for living species, genetic evidence as well.

Major branches

Spiders include Mesothelae and Opisthothelae. The latter includes Mygalomorphae, such as tarantulas, and Araneomorphae, containing many familiar web builders and hunters. These names describe relationships rather than a ranking from inferior to superior. Living lineages that branched early have also continued evolving throughout the time since their divergence.

Trees can be tested

The precise position of a branch is a scientific hypothesis. New species, fossils and methods can change it. Our group portraits therefore link names with anatomy and sources. A short museum overview cannot replace a full classification, but it can show why a tarantula and a garden spider share a body plan while differing in important details.

A fossil with a tail

Chimerarachne yingae combines spinnerets with a long tail-like appendage. The original paper used yingi; the fossil catalogue lists the corrected spelling yingae. The 2018 study shows that its precise position depends on analytical parameters. One striking feature therefore does not settle every relationship: multiple characters must be assessed together, with uncertainties made explicit.

Sources & image credits

Sources checked: 1 November 2026. Figures and records carry the qualifications stated in each article.