Madumabisa Mudstone Formation
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 and the Luangwa Basin.
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. Dicynodonts and gorgonopsians 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.
Age and regional correlations
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.Lower member
The lower member of the Madumabisa Mudstone has rare fossils of tapinocephalids, similar to the Tapinocephalus Assemblage Zone of the Karoo, about 265–260 million years ago. In other words, from the Capitanian stage of the Middle Permian epoch. The early dicynodont Abajudon is also found in the R1 member of the Ruhuhu Formation in Tanzania.Upper member
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, a little older than 256 Ma. In other words, about mid-way through the Wuchiapingian stage of the Late Permian 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.The upper assemblage has an abundance of Dicynodon, alongside other dicynodonts and other distinctive synapsids. These fossils are most consistent with the Karoo's Dicynodon–''Theriognathus subzone of the Daptocephalus Assemblage Zone, about 255–254 Ma. The DAZ extends from the later part of the Wuchiapingian stage into the succeeding Changhsingian stage. Lystrosaurids 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