The ultrastructure of the tooth enamel of small Equus of the “tarpan” group and their possible phylogenetic connections

Abstract

The paper presents the results of a comparative analysis of the ultrastructure of tooth enamel (incisors, premolars and molars) in representatives of morphologically (and possibly phylogenetically) similar forms of small horses. These are both extinct forms of tarpan – Equus gmelini from various sites of the early Holocene of Ukraine (Myrne, Kamiana Mohyla and Hirzhevo) and modern forms – konik polski and E. przewalskii, and European wild ass – E. hydruntinus. Morphology of prisms in different layers of tooth enamel and its relative relationships in various taxa were thoroughly described. The data obtained in the form of tables and graphs, with the appropriate statistical processing thereof, show the morphological similarity of tarpan remains from different sites, and their similarity to the konik polski and Przewalski’s horse. However, the European wild ass differs significantly from the other groups studied. In equines, the radial enamel varieties (types І, ІІ and ІІІ) have evolutionary tendencies to strengthen the first and second types of hydroxyapatite prisms, while reducing the share of the IPM matrix in the enamel structure. In turn, the enamel of the incisors is characterized by lamellar enamel of the HSB uniserial type.