Vassil Tzankov Tzankov (Bulgarian: Васил Цанков Цанков) (April 2, 1905, Gorna Oryahovitsa, Bulgaria – August 25, 1986, Sofia, Bulgaria) was a Bulgarian geologist and paleontologist. He is best known for his work on Upper Cretaceous ammonites and bivalves. Tzankov was head of Bulgarian Geological Survey from 1941 until 1944. In 1945 he became docent and in 1947 - professor, and was appointed to the paleontology chair at Sofia University "St. Kliment Ohridski". In the late 1950s Tzankov organized the launch and became the first editor and one of the principal authors of the multi-volume treatise "Fossils of Bulgaria" (Bulgarian: Фосилите на България). Contributors to the treatise included leading Bulgarian specialists in the field. He served as deputy director of the Geological Institute at