The Madumabisa Mudstone Formation is a geologic formation in the Middle to Late Permian of Zambia and Zimbabwe. It comprises ancient lake and river mudstone exposed in two sedimentary basins: the Mid-Zambezi Basin (on the Zambia-Zimbabwe border) and the Luangwa Basin (in northeast Zambia).
Though understudied for many years, the exposures of the Luangwa Basin are among the best records of Late Permian fossils in the world. The upper member of the Madumabisa Mudstone Formation has produced many species of synapsids (animals distantly related to mammals). Dicynodonts (herbivores with tusks and beaks) and gorgonopsians (saber-toothed predators) are particularly common. Similar species are found in the even more fossil-rich Karoo Basin of South Africa, assisting age correlation between the two regions.
The age of the Madumabisa Mudstone must be estimated from its fossil fauna, which can then be compared to the strata of the Karoo Basin in South Africa.
The lower member of the Madumabisa Mudstone has rare fossils of tapinocephalids, similar to the Tapinocephalus Assemblage Zone (TAZ) of the Karoo, about 265âÂÂ260 million years ago (Ma). In other words, from the Capitanian stage of the Middle Permian (Guadalupian) epoch. The early dicynodont Abajudon is also found in the R1 member of the Ruhuhu Formation in Tanzania.
The upper member of the Madumabisa Mudstone seems to have two distinct fossil-rich intervals in the Luangwa Basin, a lower and upper assemblage. The lower assemblage has an abundance of Oudenodon, Diictodon, and Pristerodon, alongside other dicynodonts such as Kembawacela, Endothiodon, and Odontocyclops. In the Karoo, Endothiodon and Odontocyclops only coexist near the end of the Endothiodon Assemblage Zone (EAZ), a little older than 256 Ma. In other words, about mid-way through the Wuchiapingian stage of the Late Permian (Lopingian) epoch. EAZ taxa such as Endothiodon and Gorgonops have also been found in the Mid-Zambezi Basin. Aulacephalodon is only found in a narrow band of strata between the two major assemblages. A distinct middle assemblage may be supported or refuted by future sampling. If valid, it will probably be equivalent to the Karoo's Cistecephalus Assemblage Zone (CAZ, about 256âÂÂ255 Ma).
The upper assemblage has an abundance of Dicynodon, alongside other dicynodonts (Daptocephalus, Compsodon, Digalodon) and other distinctive synapsids (Theriognathus, Procynosuchus). These fossils are most consistent with the Karoo's DicynodonâÂÂTheriognathus subzone of the Daptocephalus Assemblage Zone (DAZ), about 255âÂÂ254 Ma. The DAZ extends from the later part of the Wuchiapingian stage into the succeeding Changhsingian stage. Lystrosaurids (Euptychognathus, Madumabisa) are more common than other dicynodonts in the youngest layers of the formation, hinting at a slight overlap with the Lystrosaurus maccaigi subzone of the DAZ. There is no direct evidence that the Permian-Triassic boundary is preserved in the Madumabisa Mudstone Formation
From Peecook et al. (2025) unless cited otherwise:
Several species of Glossopteris have been found in the Madumabisa Mudstone Formation, along with other "seed ferns" (Gangamopteris, Noeggerathiopsis) and true ferns (Neomariopteris. Phyllotheca). Petrified wood is also known from the formation, including large trunks of "Dadoxylon" (Agathoxylon), up to 4 feet in diameter. Palynomorphs (spore and pollen forms) are similar to those found in the Lower Sakamena Formation of Madagascar.