A striking visual characteristic of the family, beside dimorphism, is the unusual upward bend encountered near the femur of the first pair of legs.

While resembling hydraulic muscle mechanisms akin to arthropods, this modification actually allows the spider to retain the prey directly from the crevice it occupies.

[2][3] On the basis of the features of the male and female genitalia, the family was placed in the Haplogynae, usually as the sister taxon of the remaining members of the group.

[5] They have other features which have been regarded as "primitive": an M-shaped intestine, only leg IV moving while combing silk, and posterior book lung leaves being present in early juveniles.

[5] A 2015 study, based on genomic data, places Filistatidae with Hypochilidae in a clade outside most of the families previously placed in Haplogynae:[8] Hypochilidae Filistatidae most other "traditional" haplogynes Leptonetidae Entelegynae This placement suggests that features that were thought to be "primitive" to araneomorph spiders as a whole (such as an M-shaped midgut) could actually be novel derived features (synapomorphies) of the Hypochilidae-Filistatidae clade.