The Permo-Triassic vertebrate assemblage zones (AZs) of South Africa’s Karoo Basin are a standard for local and global correlations. However, temporal, geographical, and methodological limitations challenge the AZs reliability. We analyze a unique fossil dataset comprising 1408 occurrences of 115 species grouped into 19 stratigraphic bin intervals from the Cistecephalus, Daptocephalus, Lystrosaurus declivis, and Cynognathus AZs. Using network science tools we compare six frameworks: Broom, Rubidge, Viglietti, Member, Formation, including a framework suggesting diachroneity of the Daptocephalus/Lystrosaurus AZ boundary (Gastaldo). Our results demonstrate that historical frameworks (Broom, Rubidge) still identify the Karoo AZs. No scheme supports the Cistecephalus AZ, and it likely comprises two discrete communities. The Lystrosaurus declivis AZ is traced across all frameworks, despite many shared species with the underlying Daptocephalus AZ, suggesting the extinction event across this interval is not a statistical artifact. A community shift at the upper Katberg to lower Burgersdorp formations may indicate a depositional hiatus, which has important implications for regional correlations and Mesozoic ecosystem evolution. The Gastaldo model still identifies a Lystrosaurus and Daptocephalus AZ community shift, does not significantly improve recent AZ models (Viglietti), and highlights important issues with some AZ studies. Localized bed-scale lithostratigraphy (sandstone datums), and singleton fossils cannot be used to reject the patterns shown by hundreds of fossils, and regional chronostratigraphic markers of the Karoo foreland basin. Meter-level occurrence data suggest that 20–50 m sampling intervals capture Karoo AZs, unifying the use of meter-level placements of singleton fossils to delineate biozone boundaries and make regional correlations.

Dataset 1 includes metadata for 1408 fossils collected from the Cistecephalus, Daptocephalus, Lystrosaurus declivis, and Cynognathus Assemblage Zones of South Africa's Karoo Basin. The dataset is the collation and extension of previous datasets compiled by Van der Walt et al. (2011) (historic collections) and more recent fossil collections by Smith and Botha-Brink (2014), Botha et al. (2020), and Viglietti et al. (2021). These fossils represent 115 species grouped into 19 stratigraphic bin intervals. Bin intervals represent correlative stratigraphic intervals defined by field documentation of lithostratigraphic units and their thicknesses. Formalised definitions of lithostratigraphic units (South African Committee for Stratigraphy, 1980) and 1:250 000 geological maps (i.e., 3024 Colesburg, 3026 Aliwal North, 3124 Middelburg, and 2826 Winburg) were also used. These lithostratigraphic metadata helped group fossil specimens at meter-level precision in the bin-interval framework and allowed for correlation between field locations. Specimen data for these occurrences include accession and/or field number, species identification, location (farm name and GPS position), litho- and biostratigraphic position, and bin interval position.

Specimen data in Dataset 1 includes stratigraphic data (Bin Interval, Section upper boundary, in meters), repository data (Accession number, Field number), location data (Province, Study site, Farm location), species data (Superorder, Clade, Genus, and Species).

Microsoft Excel and RStudio.