The Triassic–Jurassic Upper Karoo Group of the Mid-Zambezi Basin (MZB; Zimbabwe) includes a thick succession of terrestrial sediments with high palaeontological potential that has been neglected since the 1970s. Here, we review the Upper Karoo Group stratigraphy, present detailed sedimentological work and identify new vertebrate-bearing sites at several measured sections along the southern shore of Lake Kariba. These fossil-bearing sites fall within the Pebbly Arkose and Forest Sandstone formations, and are the first to be recorded from the region since the discovery of Vulcanodon karibaensis nearly 50 years ago. The unique and diverse assemblage of aquatic and terrestrial fauna reported includes phytosaurs, metoposaurid amphibians, lungfish, non-dinosaurian archosauromorphs and non-sauropod sauropodomorph dinosaurs. This improvement of Upper Karoo Group biostratigraphy is important in refining its temporal resolution, and impacts both regional and global studies. Finally, the new fossil sites demonstrate the palaeontological importance of the MZB and its role in providing a holistic understanding of early Mesozoic ecosystems in southern Gondwana.

The paraphyletic genus ‘Paleorhinus’ is understood currently as a cosmopolitan phytosaur taxon from the Late Triassic. There is no consensus regarding the number of species of ‘Paleorhinus,’ with multiple species and genera synonymised into a single genus or even a single species at various points in its published history. The taxonomy is confounded by historical descriptions without the benefit of comparisons to more recently collected specimens, emphasis on plesiomorphic cranial morphology as diagnostic features of the genus, and lack of cladistic analyses. When included in a recent explicitly cladistic phylogenetic analysis, the holotype of ‘Paleorhinus’ scurriensis (TTU P-00539) was found to be the earliest-branching phytosaur with respect to other North American specimens previously referred to ‘Paleorhinus,’ and is generically distinct from Paleorhinus. ‘Paleorhinus’ scurriensis differs from all known phytosaurs in five unambiguous characters: basitubera widely separated mediolaterally; ridge present on lateral surface of jugal; thickened shelf present along posteroventral edge of expanded pterygoid-quadrate wing; ‘septomaxillae’ separated and excluded from internarial septum; and nasal swelling present posterior to posterior borders of nares. This detailed morphological description of an early-branching phytosaur taxon is a first step towards resolving long-standing issues surrounding specific anatomical features and relationships among early members of the clade.