include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families. External relationships The spiders (Araneae) are monophyletic (i.e., a clade, consisting of a last common ancestor and all of its descendants). There has been debate about what their closest evolutionary relatives are, and how all of these evolved from the ancestral chelicerates, which were marine animals. This 2019 cladogram illustrates the spiders' phylogenetic relationships. Arachnids lack some features of other chelicerates, including backward-pointing mouths and gnathobases ("jaw bases") at the bases of their legs; both of these features are part of the ancestral arthropod feeding system. Instead, they have mouths that point forwards and downwards, and all have some means of breathing air. Spiders (Araneae) are distinguished from other arachnid groups by several characteristics, including spinnerets and, in males, pedipalps that are specially adapted for sperm transfer. Internal relationships The cladogram shows the relation among spider suborders and families: Taxonomy The order name Araneae derives from Latin aranea borrowing Ancient Greek arákhnē from arákhnēs. Spiders are divided into two suborders, Mesothelae and Opisthothelae, of which the latter contains two infraorders, Mygalomorphae and Araneomorphae. Some 50,356 living species of spiders (order Araneae) have been identified, grouped into 132 families and 4,280 genera by arachnologists in 2022. Mesothelae The only living members of the primitive Mesothelae are the family Liphistiidae, found only in Southeast Asia, China, and Japan. Most of the Liphistiidae construct silk-lined burrows with thin trapdoors, although some species of the genus Liphistius build camouflaged silk tubes with a second trapdoor as an emergency exit. Members of the genus Liphistius run silk "tripwires" outwards from their tunnels to help them detect approaching prey, while those of the genus Heptathela do not and instead rely on their built-in vibration sensors. Spiders of the genus Heptathela have no venom glands, although they do have venom gland outlets on the fang tip. The extinct families Arthrolycosidae, found in Carboniferous and Permian rocks, and Arthromygalidae, so far found only in Carboniferous rocks, have been classified as members of the Mesothelae. Mygalomorphae The Mygalomorphae, which first appeared in the Triassic period, are generally heavily built and ″hairy″, with large, robust chelicerae