Bone ornamented items of the end of the Paleolithic — Mesolithic periods are very rare in the south of Western Siberia. While some of them have dating context, others are accidental finds. Despite the circumstances of their discovery and limited amount of relevant information, there is a need to consider the issues of dominant subjects, compositional morphology, technical execution of ornaments covering their surfaces and relations with the materials of adjacent territories, mainly the Ural region. The study presents the results of a palaeographic analysis of ornamental patterns (texts) created presumably in the Epipaleolithic and which are rather rare in terms of morphology. The study is focused on the ornament of a dagger from Aytkulovo. The bone artefact was accidentally discovered in July 1976 near the village of Aytkulovo on a shoal at the mouth of River Murlinka (Tara district, Omsk region). Stylistic and compositional analogues of the dagger in the Middle Irtysh region are unknown. The preservation of the artefact is satisfactory, which allows analyzing its ornamental composition. The dagger’s ornamentation consists of two iconic layers, each of them can be attributed to different chronological episodes (phases). Such combination of the non synchronous ornamental texts on a single artefact is a true rarity in paleoornamentology. While objects of the first ornamental layer form the frame of the composition, the overlapping additional elements of the second layer were added in a later chronological episode. The observed differences of the first and the second layers in specific taphonomic, technological, stylistic and graphic features raise the question of a chronological gap in their creation. The graphic and stylistic originality of the iconic design of the dagger suggests that its ornamental pattern can be considered as a “graphic dialect” belonging to a more global ornamental tradition (its preliminary name was “Ural-Chernoozerye”). The obtained results confirm the being-developed thesis about the existence of a single cultural community in the southern Trans-Urals and in the south-west of Western Siberia during the late Palaeolithic — early Mesolithic period. This community is represented by the local mutually contacting groups which used similar graphic principles of information transfer. The process of interpenetration and blending of local traditions led not only to exchange of technological innovation but also to emergence of the composite graphic “dialects” similar to the one in Aytkulovo.