Aptian

The offering work covers the history of the Aptian stage stratigraphy and ammonites studies of the central part of the Northern Caucasus. Its first part, devoted to the history of the mid-19th century to the mid-20th century, was published earlier. In this paper the fourth (1970– 1989) and fifth (1990 – present) stages are reviewed. The fourth was marked by the acceptance of tripartite division of the Aptian, including the Clansayesian as the upper substage into it, at the end of this stage some summary works were published.

The offering paper covers the history of the Aptian stage stratigraphy and ammonites studies of the central part of the Northern Caucasus, which was subdivided by the author into five stages. The first (mid-to-late 19th century), second (1901–1951) and third (1952–1969) stages are reviewed. The first is associated with the beginning of research in the region, at this time the attempts of the stage and substage dividing were made.

The representatives ofthe genusEpicheloniceras Casey, 1954fromthe Middle Aptian of Mangyshlak, Western and Southern Turkmenistan are described.

The article presents the study results of the ammonite subfamily Cheloniceratinae Spath, 1923 representatives (genera Cheloniceras Hyatt, 1900 and Epicheloniceras Casey, 1954) fromthe Lower and Middle Aptian of Mangyshlak, Western and Southern Turkmenistan. The diversity and stratigraphic distribution of species is assessed, intraspecific variability is identified and typified. Representatives of the genus Cheloniceras are described.