Muiria hortenseae, sometimes called the mouse head mesemb or muiskopvygie (Afrikaans), is a rare dwarf leaf succulent. The genus Muiria is monotypic, consisting of only one species. M. hortenseae used to be called Gibbaeum hortenseae. It hybridises in nature with G. album.
The leaves are paired, the pairs fused together in rounded to ovoid bodies, covered in a soft fur. A leaf-body becomes about 3 cm in diameter. A new leaf-pair grows from the central slit in the old one that loses its succulence and becomes a protective cloak over the new leaf-body for a period. Old plants form small clumps.
The single, waxy white or pale pink flowers appear on the tops of the rounded leaves in spring and summer. Petals in the rows closer to the flower centre are progressively shorter.
Fruit capsules have six locules. The seeds are small, brown and smooth.
The species distribution is restricted to a few areas in the Tanqua Karoo, near Barrydale in the Little Karoo and north of Riversdale.
The habitat is succulent Karoo in quartzite and clay soil. The plant is considered to be critically endangered in its habitat early in the twenty first century, due to harvesting, habitat degradation and destruction (Vlok and Schutte-Vlok, 2015; Wikipedia; www.bidorbuy.co.za; http://redlist.sanbi.org).