The work provides the first systematic summary of primitive archosaurs - tecodonts from the Permian and Triassic of Eastern Europe. 19 genera and 22 species belonging to 4 families are described. Of these, 9 genera and 9 species were established by the author, including the first euparkeriids from Eastern Europe and the world's oldest early Triassic rauisuchids. The transition from lateral to parasagittal limb staging in archosaurs is analyzed. The ecological role of tecodonts in Permotrias terrestrial communities is considered. For the first time, guiding complexes of diapsids are distinguished for fractional stratigraphic units of Eastern Europe. For paleontologists, zoologists, ecologists, stratigraphic geologists.