In the described male and female, the rear edge of the abdomen is indented.
The abdomen is dark brown with lighter round patches and white and brown hairs. The legs are light brown with darker rings.
Madagascarchaea jeanneli has an elevated head region and long legs. In the 2018 description, the first femur was 2.60–3.06 times carapace length in five males and 2.88–3.12 times in five females. The illustrated male had chelicerae 1.18 mm long, with a small downward-pointing spine near the base.
The same study reconsidered spiders previously grouped under this name. Detailed male reproductive structures supported recognizing previously illustrated male and female specimens as Madagascarchaea lotzi. The old type series contains females, which are difficult to distinguish among these closely similar species. The authors therefore used the type locality to propose an association with nearby males, combining morphology and locality in their revised interpretation.
An extinction-risk assessment has not been added yet.
At Analamazaotra Forest Station, where females were assigned to this species, the managing association Mitsinjo has undertaken forest restoration. Its May 2023 report describes seedling production begun with the US Forest Service in 2021, a new nursery and greenhouse, and native-tree planting that started at a restoration site on the forest’s southwestern edge in 2023. The work includes checking nursery growth and planning follow-up monitoring.