Right lateral and frontal view of fossil elephant cranium KNM-ER 63642, Loxodonta adaurora, from 4.5 million-year-old Ileret, Kenya. Greatest length of the cranium is 1367 millimeters (mm) and greatest width is approximately 914 mm. Images originally produced as 3D scans by Timothy Gichunge Ibui, National Museums of Kenya and Turkana Basin Institute. Photo courtesy of William Sanders, University of Michigan Museum of Paleontology.
Field survey in remote settings near Ileret on the north-east side of Lake Turkana, Kenya by a paleontological team of the Turkana Basin Institute/Koobi Fora Research Project led to the recovery of a nearly complete elephant cranium dated to 4.5 million years. The cranium is impressively immense in size, from a massive adult male, and is the only well-preserved cranium known from the time between the origin of elephants at 8 million years until 3.5 million years ago, an interval covering more than half of the existence of the family Elephantidae. Recovery, preparation, conservation, dating, description and identification of the cranium involved collaborative work between researchers and technicians from the Turkana Basin Institute, National Museums of Kenya, University of Michigan, Rutgers University, Smithsonian Institution, and the University of Utah, led by the famous fossil hominid hunters Meave and Louise Leakey. Drs. Meave and Louise Leakey are National Geographic Explorers-at-Large and the Koobi Fora Research Project is funded by grants from the National Geographic Society.
Short time-lapse video of the excavation of Loxodonta adaurora cranium KNM-ER 63642. The cranium was recovered from Area 14, Ileret Region, Kenya, from 4.5 million-year-old sediments of the Lonyumun Member of the Koobi Fora Formation. The excavation team is part of the Koobi Fora Research Project, funded by grants from the National Geographic Society. Video courtesy of Louise Leakey, Turkana Basin Institute and National Geographic Explorer-at-Large.
Comparative study of the cranium was undertaken by Dr. William Sanders (University of Michigan Museum of Paleontology [UMMP]), who has worked widely in Africa and Arabia for nearly 40 years investigating the evolution and ecology of fossil elephants and their proboscidean relatives. The results of the comparative study and collaborative project are now published in the journal Palaeovertebrata. All figures in the publication were created and organized by Carol Abraczinskas, UMMP scientific illustrator.
Meave Leakey and William Sanders examining the Loxodonta adaurora cranium KNM-ER 63642 in its plaster jacket at the Ileret research facility of the Turkana Basin Institute. Photo courtesy of Steve Jabo, Smithsonian Institution.
Features of the molars in the cranium demonstrate that the species to which the cranium belongs is Loxodonta adaurora, a close relation but not ancestor of the extant African savanna and forest elephants, Loxodonta africana and Loxodonta cyclotis. During the duration of the Pliocene existence of Loxodonta adaurora, grasslands were expanding in Africa and numerous mammals, including horses, antelopes, rhinos, pigs, hippos and elephants, were becoming grazers and competing for C4 grasses. Isotopic study of dental enamel shows, within this ecological shift, that individuals of Loxodonta adaurora ate substantial amounts of C4 grasses. The new cranium reveals that unlike earlier elephants, whose morphology lagged behind behavior, Loxodonta adaurora had an unexpectedly advanced skull, raised and compressed from front to back, which achieved a rearrangement of chewing muscles to be more powerful and efficient for horizontal fore-aft shearing of grasses. Additionally, its molars were higher-crowned and had thicker coatings of cementum than those of earlier elephants, better for surviving wear from the coarse grit and opal phytoliths that grazers encounter eating grasses close to the ground. The evident synchronization of morphological adaptations and feeding behavior revealed by this study of Loxodonta adaurora may explain why it became the dominant elephant species of the early Pliocene.
Video of the three-dimensional scan of the nearly complete Loxodonta adaurora cranium KNM-ER 63642 from the Ileret Region, Kenya. The cranium is from a massive-sized adult male estimated to have been between 30 and 34 years old at death. Greatest length of the cranium is 1367 millimeters (mm) and greatest width is approximately 914 mm. Elephants with crania of this size are estimated to weigh nine tons and stand about 12 feet at the top of the shoulder. Image scanned by Timothy Gichunge Ibui, National Museums of Kenya and Turkana Basin Institute. Video courtesy of Louise Leakey, Turkana Basin Institute and National Geographic Explorer-at-Large.
Human evolution may be linked to the successes of these Pliocene elephants, whose presence on the landscape altered woodland and forest habitats to create more open conditions that favored the activities and adaptations of our first bipedal hominin ancestors. From this perspective, it is ironically tragic that current human activities of encroaching land use, poaching, and human-driven climate change are now threatening the extinction of the mammal lineage that helped us to begin our own evolutionary journey.