Mesothelae

The Mesothelae are a suborder of spiders (order Araneae). The division of extant members of the suborder into families has varied. A single extant family Liphistiidae may be accepted, with two subfamilies: Liphistiinae, containing only the genus Liphistius, and Heptathelinae, with seven genera. Alternatively, the two subfamilies may be treated as separate families, Liphistiidae and Heptathelidae. As of November 2025, the World Spider Catalog accepted the single family approach. There are also a number of extinct families.

This suborder is thought to form the sister group to all other living spiders, and to retain ancestral characters, such as a segmented abdomen with spinnerets in the middle and two pairs of book lungs. Extant members of the Mesothelae are medium to large spiders with eight eyes grouped on a tubercle. They are found only in China, Japan, and southeast Asia. The oldest known Mesothelae spiders are from the Carboniferous, over 300 million years ago.