The described female has a reddish-brown carapace, long jaws and legs.
In the described female, the front of the abdomen is dark brown with light round patches, while the rear is pale tan. The abdomen bears white and brown hairs.
Eriauchenus mahariraensis is a small spider with a relatively short, constricted neck-like region. It has four small spines on the crown of the head and a spine near the base of each long jaw.
Described in 2003 in Afrarchaea, it had initially been assigned using carapace shape. The 2018 revision examined the female genital structures and found no keel on the sclerotized plate, but a posterior bar was present.
These features supported its transfer to Eriauchenius, now spelled Eriauchenus. The reassessment illustrates how similar overall body shapes can accompany different internal structures, and how detailed examination can change the grouping of museum specimens.
An extinction-risk assessment has not been added yet.
Madagascar National Parks identifies selective logging, bamboo collection and gold mining among pressures on Ranomafana. It reports patrols, ecological monitoring and reforestation through a 2017–2022 project. Surveys of historical collecting sites and forest-floor material, including dead ferns, could clarify this spider’s occurrence.