His father was Alexander Fedorovich Orlov (1855-1940), member of Narodnaya Volya, official of Udel department of Vologda and Arkhangelskls Governorates. His mother was Vera Pavlovna Tumarkin (1862-1899), from Bessarabian Jewish merchants family, the older sister of Anna Tumarkin. She served as an otolaryngology doctor at S.t Petersburg's Conservatory. Orlov studied zoology and anatomy at the State University of St. Petersburg under A.A. Zavarzin. He then taught from 1916 to 1924 at the Medical Faculty of the University of Perm, during the Russian Civil War turmoil under some very difficult conditions. and from 1924 to 1935 at the Institute for Brain Research and the Military Medical Academy in Leningrad. At that time, he studied the nervous system of arthropods. From 1925 he de- voted his research interests to paleontology, the old love of his youth, and joined A. A. Borisyack. He taught at the Mining Academy in Leningrad and from 1939 at the Lomonosov State University in Moscow. He was the chief editor of a fifteen-volume series "Fundamentals of pale- ontology". In 1967 he was awarded the Lenin Prize posthumously. Director of the Paleontological Institute, The Academy of Sciences of the USSR (1945-1966). Asig- nificant part of hisscientificactivities tookwork on extinct mammals.