As a scientist, he was the first to distinguish between the genus Archaeopteryx and the genus Archaeornis; he also discovered new characteristics of the genera Tritylodon and Moeritherium. Petronijević's great scientific fame, however, is nearly eclipsed by his still greater philosophical renown, which he owes to his three principal philosophical works, Principi Metafizike (Principles of Metaphysics), O Vrednosti života (About Value of Life), Istorija novije filozofije (History of a Newer Philosophy).Branislav Petronijević, world-renowned Serbian philosopher and paleontologist, was born in a small village of Sovljak, near Ub, Serbia, on the 25th of March 1875, the son of a priest, originally from Montenegro. He had as a youth a taste for collecting objects of natural history and other curiosities while a student at a gymnasium (high school) in Valjevo and the Grande école in Belgrade. This led him to the study of medicine, which he went to Vienna to pursue, eventually after the third semester directing his attention to psychiatry, philosophy, biology and paleontology. Petronijević joined the Philosophical Society of the University of Vienna and studied under Ludwig Boltzmann. After years in Vienna he travelled to Germany with a view to further philosophical study. There he studied at the University of Leipzig under Johannes Volkelt, Wilhelm Ostwald, and Ernst Mach. With his metaphysical writings,"Der ontologische Beweis fűr das Dasein des Absoluten," he proved himself a worthy student of Professor Wilhelm Wundt, "the father of experimental psychology," successfully defending his thesis in 1898. From Leipzig he went back to Belgrad, where he wrote and published "Der Satz vom Grunde" in 1898. It was during this period, however, that he thought out and developed what is distinctive in his philosophical doctrine. His eclecticism, his ontology and his philosophy of history were declared in principle and in most of their salient details in the "Prinzipen der Metaphysik" (2 volumes, Heidelberg, 1904–1911) and "Die typischen Geometrien und das Unendliche" (Heidelberg, 1907). In 1898 he was given the post of privatdozent in the Grande école of Belgrade and seven years later when his alma mater became the University of Belgrade he was appointed associate professor. At the outbreak of World War I he turned to journalism, becoming a war correspondent for the Serbian War Office Press Bureau, induced by Col. Dragutin Dimitrijević, his childhood friend. In 1915 he joined the Serbian army's retreat through Albania (World War I). After reaching Greece, he was sent to London with the Serbian Legation, along with politician Nikola Pašić, geographer Jovan Cvijić, professors Bogdan Popović and his brother Pavle Popović. A man who impressed me, not so much by his ability as by his resolute absorption in philosophy even under the most arduous circumstances, was the only Yugoslav philosopher of our time, whose name was Branislav Petroniević. I met him only once, in the year 1917. The only language we both knew was German and so we had to use it, although it caused people in the streets to look at us with suspicion. The Serbs had recently carried out their heroic retreat before the German invaders, and I was anxious to get a first-hand account of this retreat from him, but he only wanted to expound his doctrine that the number of points in space is finite and can be estimated by considerations derived from the theory of numbers. The consequence of this difference in our interests was a somewhat curious conversation. I said, "Were you in the great retreat?" and he replied, "Yes, but you see the way to calculate the number of points in space is." I said, "Were you on foot?" and he said, "Yes, you see the number must be a prime." I said, "Did you not try to get a horse?" and he said, "I started on a horse, but I fell off, and it should not be difficult to find out what prime." In spite of all my efforts, I could get nothing further from him about anything so trivial as the Great War. I admired his capacity for intellectual detachment from the accidents of his corporeal existence, in which I felt that few ancient Stoics could have rivalled him. After the First War he was employed by the Yugoslav Government to bring out a magnificent edition of the eighteenth-century Yugoslav philosopher Boscovic, but what happened to him after that I do not know.

After the war he left London and went back to his teaching post at the University of Belgrade, where he was appointed extraordinary professor (1919). In 1920, he was elected into the Serbian Royal Academy and at the same time he attracted the notice of other foreign philosophers with whom he had a lively correspondence in both philosophy and science. He wrote numerous papers on philosophy and science in English, French, German, Polish and Serbian learned journals.

We see in "L'Évolution universelle" very distinctly the fusion of the different philosophical influences by which his opinions were finally matured. For Petronijević was an eclectic in thought and habit of mind as he was in philosophical principle and system. It is with the publication of the L'Évolution of 1921 in Paris that the first great widening of his reputation is associated.

Also, he undertook the task to translate Ruđer Bošković's "A Theory of Natural Philosophy" mentioned by Russell. As far as we know, this is the first time that the work was translated from Latin to a modern language (English). It is prefaced by the "Life of Roger Joseph Boscovich," written in English by Branislav Petronijević, and an explanatory introduction by the translator. Bošković's "A Theory of Natural Philosophy" is a work of considerable importance in the history of physical theory and his atomic hypothesis were of particular interest when it was first published in London by Open Court Publishing Company in 1922. Petronijević retired from the university in 1927. Ksenija Atanasijević was one of his disciples. He stopped working altogether from the time the Axis invaded the Kingdom of Yugoslavia (1941) until his death. He was staunch anti-fascist and anti-communist and could not accept the fact that Yugoslavia was dragooned behind the Iron Curtain. Perhaps for this reason he was left ignored and forgotten, like most of his post-World War I colleagues who were in sympathy with the Old Order. His old age was spent in obscure poverty, his friends and associates having fled to the West, killed in the war, or passed away before him. Petronijević died in a Belgrade hotel on the 4th of March 1954. He was 79. He never married.