A different view of the abdomen
Living mesotheles have visible plates on the abdomen and spinnerets positioned nearer the middle of its underside. Such characters distinguish them from other living spiders. They help comparisons; they do not imply an inferior or unfinished animal.
An early-diverging branch
Phylogenetic trees place Mesothelae as the sister group of all other living spiders. Their living representatives occur in parts of Asia. They are present-day tips of a long branch, not living ancestors of tarantulas or orb weavers.
Fossils are points of comparison
Retaining an ancestral character does not mean an organism has remained unchanged. Researchers also investigate relationships and species boundaries within living mesotheles. Fossils and living animals can be compared through characters; they provide neither a continuous film nor a species frozen since ancient times.
Sources & image credits
- Xu et al. (2015) · A genus-level taxonomic review of primitively segmented spiders ↗
- Garrison et al. (2016) · Spider phylogenomics: untangling the Spider Tree of Life ↗
- Traiyasut et al. (2024) · Molecular phylogeny, biogeography, and species delimitation of Liphistius in Thailand ↗
Sources checked: 2 November 2026. Comparisons carry the qualifications stated in each article.