Reflexes of proto-Mongolian vowels in South Mongolian languages

The Mongolian languages are a language family that includes several closely related languages of Mongolia, China, Russia and Afghanistan. According to lexicostatistics, they broke up around the 5th century AD. Dagur, Shira-Yugur, Dongxiang, Bao'an, Tu (Monguor) are commonly referred to as South Mongolian languages. The South Mongolian languages, in comparison with other groups of Mongolian languages, were influenced by Chinese and Turkic languages, various historical events had an undoubted influence on them.