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.<ref>{{cite book |author1= Tzankov, V.|author2=Pamouktchiev, A. |author3= Tchechmedjieva, V. |author4=Motekova, N. |year=1981 |title= Les fossiles de Bulgarie V Crétacé supérieur. Grandes foraminifères, Anthozoaires, Gastéropodes, Bivalvia |publisher= Éditions de L'Académie bulgare des sciences |place= Sofia}}</ref> 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 the Committee for Geology and Mineral Resources in the period 1960-1966. From 1967 to 1982 Tzankov also served as head of the Department of Paleontology with the Geological Institute at the Bulgarian Academy of Sciences. In 1967 he was elected as a corresponding member of the Bulgarian Academy of Sciences. Early life Tzankov was raised in Shumen in the family of a veterinary physician, Dr. Tzanko Tzankov (1869-1941). After attending high school in Shumen, he enrolled in Sofia University, taking his undergraduate degree in natural history in 1929. He took his PhD in 1929, under the supervision of Dr. Stephan Bonchev and became the first student to be awarded a doctorate in natural science in Bulgaria. His dissertation was regional paleontological survey of Shumen plateau, and in particular, stratigraphy and paleontology of the Upper Cretaceous fossils in Northeastern Bulgaria. Early career Tzankov commenced work as an assistant professor in geology at Sofia University in 1930. He did postgraduate research in Vienna (1936), Paris (1938–39) and Berlin (1941). In 1939, he was appointed chief of the Geology section at the Ministry of Trade, Industry and Labour. In 1941, he was appointed head of Geology Research within the newly established directorate “Natural Resources”. During that period he introduced micropaleontological research – foraminifera, conodonts, spores and pollen – in Bulgaria. In 1945 he resumed his academic work at Sofia University. In 1947, he was promoted to full professor. He would alternate in his role of director of