Ordovician conodonts from the Thong Pha Phum area, western Thailand

The Ordovician conodont biostratigraphy of a limestone sequence in the Tha Manao Formation, exposed in the Thong Pha Phum area, western Thailand, comprises four Early to Middle Ordovician conodont zones. These are the Juanognathus variaviris Zone, the Walliserodus comptus Zone, the Juanognathus jaanussoni–Histiodella holodentata Zone, and the Plectodina onychodonta Zone, in ascending order. These conodont faunas are similar to those from the Midcontinent Province, North China, Australia, and Argentina.