Lanthanostegus is an extinct genus of non-mammalian synapsids from the Capitanian Tapinocephalus Assemblage Zone, Koonap Formation (Beaufort Group) of South Africa.

The type and the only species is Lanthanostegus mohoii.

The animal was named as Lanthanocephalus mohoii by Modesto et al. in 2002[3] but was recombined as Lanthanostegus mohoii in 2003, as the genus Lanthanocephalus was preoccupied by a coral.

[2] The topology follows Duhamel et al.

[4] Eodicynodon Colobodectes Lanthanostegus Pylaecephalidae Endothiodontia Emydopoidea Pristerodon Bidentalia