Fossil Involucres Of Carpinus And Their Significances From The Duho Formation Of Yeonil Group, Korea

This paper studied the fossil involucres of Carpinus from the Duho Formation of Yeonil Group, Korea and the involucres are classified into five species as follows; Carpinus subcordata Nathorst, C. stenophylla Nathorst, C. kodairae-bracteata Huzioka, C. miofargesiana Tanai and Onoe, and C. oblongibracteata Hu and Chaney. The occurrence of the last three species is their first record in the Yeonil Group. Compared to the seven Neogene floras of the Korean Peninsula, Carpinus in the Yeonil flora shows the highest species diversity. This probably reflects that the annual mean temperature of the Pohang area was about 2. lower than that of the present day. During the Early to Middle Miocene of the Korean Peninsula, the number of fossil species is much larger than that of modern species, which is also probably due to the lower annual mean temperature of the Korean Peninsula at that time. Speciation of Carpinus in the East Asia shows different patterns depending on area and period. In Japan, the speciation mostly took place at the end of the Oligocene, and Carpinus greatly flourished in the Early Miocene. On the other hand, it is presumed that the speciation in the Korean Peninsula and China took place mostly in the Early Miocene and Carpinus greatly flourished in the Middle Miocene. Four species belonging to the form group C. cordata of section Distegocarpus on the Korean Peninsula were all extinct during the Neogene. C. cordata, which has a relationship with C. subcordata Nathorst, is present in the Korean Peninsula. C. subyedoensis Konno belonging to the form group C. orientalis of section Eucarpinus was extinct during the Neogene. However, C. tschonoskii, which has a relationship with C. subyedoensis, is present in the Korean Peninsula.