Mygalomorphs are capable of spinning at least slightly adhesive silk, and some build elaborate capture webs that approach a metre in diameter.

[4] Some flies in the family Acroceridae that are endoparasites of mygalomorphs may remain dormant in their book lungs for as long as 10 years before beginning their development and consuming the spider.

[7] An older name for the group is Orthognatha, derived from the orientation of the fangs which point straight down and do not cross each other (as they do in the araneomorphs).

Megarachne servinei was thought to be a giant mygalomorph from the Upper Carboniferous (about 350 million years ago), but was later found to be a eurypterid.

[3] Rosamygale belongs to Avicularioidea, based on the absence of an abdominal scutum and well-separated posterior lateral spinnerets.

[14] The relationships of taxa in the Mygalomorphae were restructured based on a comprehensive phylogenetic study by Opatova et al. (2020)[15] The generic composition of the families Ctenizidae, Cyrtaucheniidae, Dipluridae, and Nemesiidae were relimited.

The preferred cladogram from Optova et al. (2020) is:[15] Hexurellidae Mecicobothriidae Atypidae Megahexuridae Antrodiaetidae Ischnothelidae Microhexuridae Hexathelidae Euagridae Porrhothelidae Macrothelidae Paratropididae Stasimopidae Atracidae Actinopodidae Halonoproctidae Migidae Idiopidae Ctenizidae Euctenizidae Bemmeridae Barychelidae Theraphosidae Nemesiidae Pycnothelidae Dipluridae Cyrtaucheniidae Anamidae Entypesidae Microstigmatidae In 1802, C. A. Walckenaer separated mygalomorph spiders into a separate genus, Mygale, leaving all other spiders in Aranea In 1985, Robert Raven published a monograph of the Mygalomorphae in which he proposed an internal classification for the Mygalomorphae, based on morphological features.

Ignoring these unusual rank names, his classification can be shown diagrammatically:[17] Mecicobothriidae Microstigmatidae Hexathelidae Dipluridae Nemesiidae Theraphosidae Paratropididae Barychelidae Atypidae Antrodiaetidae Cyrtaucheniidae Idiopidae Ctenizidae Migidae Actinopodidae Subsequent research, largely based on molecular phylogenetic studies, has not upheld some of Raven's groupings.

[15] Most members of this infraorder occur in the tropics and subtropics, but their range can extend farther north, e.g. into the southern and western regions of the United States.