Oval Calamistrum Clade Spiders (Zoosubsection Oval calamistrum clade)

The Oval calamistrum clade is a zoosubsection within the RTA clade (Zoosection RTA clade) of the infraorder Entelegynae (Order Araneae). This lineage represents a specialized group of entelegyne spiders distinguished primarily by the morphology of the calamistrum, a comb-like structure of setae located on the metatarsus of the fourth pair of legs in females and used in silk processing.

Members of the Oval calamistrum clade are characterized by having a short, compact, and oval-shaped calamistrum, in contrast to the elongated or linear calamistrum found in other cribellate spider groups. This structure is associated with the production and manipulation of cribellate silk, a non-adhesive, wool-like silk used to entangle prey. The presence of an oval calamistrum reflects a distinct evolutionary adaptation in silk use and web construction.

Morphologically, spiders in this clade are typically small to medium-sized and may exhibit diverse body forms depending on the family or genus. Despite this diversity, they share common entelegyne reproductive features and the defining RTA clade characteristic of a retrolateral tibial apophysis in the male pedipalp. Coloration is often cryptic, aiding in camouflage within their preferred habitats.

Ecologically, the Oval calamistrum clade includes spiders that are primarily cribellate web builders, constructing specialized capture webs or retreats using cribellate silk. These spiders occupy a range of environments, including forest understories, leaf litter, bark surfaces, and rock crevices. Their hunting strategy relies on the physical entanglement of prey rather than adhesive glue droplets.

The Oval calamistrum clade represents an important evolutionary branch within the RTA clade, highlighting the diversification of silk-use strategies among entelegyne spiders. It includes several lineages traditionally associated with cribellate families, contributing to the structural and ecological diversity of modern spider assemblages.