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. , 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.