Skull of Proconsul from Rusinga Island

Abstract

THE second season‘s work of the British-Kenya Miocene Expedition in the Kavirondo region of Lake Victoria has culminated in one of the most important discoveries yet made there. Dr. L. S. B. Leakey, the field director of the Expedition, has announced the finding on Rusinga Island on October 2 of the greater part of a skull of one of the species of Miocene apes belonging to the genus Proconsul, probably Pr. africanus (Hopwood). Up to now, fossil remains of Miocene and Pliocene apes in Africa and other parts of the world have been practically confined to teeth and fragments of jaws, and this new discovery for the first time provides information regarding the whole of the facial skeleton and much of the brain case. As will be seen from the accompanying photograph, the jaws and facial skeleton are remarkably complete, though they are somewhat displaced by distortion on the left side. The forehead region is particularly interesting, for it shows a complete absence of the supra-orbital torus which is so characteristic of the modern African anthropoid apes. Another interesting feature is the unusual thinness of the cranial wall. The specimen is extremely fragile, and evidently must have required consummate skill for its successful removal from the deposits in which it was found. Mrs. Leakey was actually the first to see some small fragments of the skull, where they had been washed out on the slope of one of the gullies which were being explored. She directed the attention of her husband who, cutting back into the beds, brought to light this most important, and indeed unique, fossil. Mrs. Leakey is bringing the skull by air to Great Britain, where she expects to arrive on October 31, and in the first instance it will be deposited at the Department of Human Anatomy at Oxford, where it will be studied in detail, in connexion with more than a hundred other specimens of Miocene fossil apes which the British-Kenya Miocene Expedition has collected over the last two years. It is particularly gratifying to note that this Expedition, which was mainly financed in its first year (1947) with the aid of a grant from the Royal Society, has proved such an outstanding success. Apart from the fine collection of fossil Primate material, many hundred specimens of other Early Miocene vertebrates have also been accumulated.