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With the foramen magnum being position anterior in the cranium, the body of bipedal mammals is given a different center of gravity compared to quadrupedal mammals. The anterior foramen magnum shifts the weight of the body more to the mammals' pelvis and femur, present in some primates, like great apes.
The forehead of the chimpanzee receded to form a heavy browridge and a jutting jaw; the Taung Child's forehead recedes but leaves no browridge. Its foramen magnum, a void in the cranium, where the spinal cord is continuous with the brain, is beneath the cranium so the creature must have stood upright. [33] This is an indication of bipedal ...
The skull was an indicator of orthograde posture because of the location and orientation of the foramen magnum. The foramen magnum is the space in the skull that acts as the bridge to the central nervous system from the spinal cord to the brain. For animals with "pronograde posture, the foramen magnum is dorsally oriented, whereas in humans it ...
The base of the cranium is formed from a ring of bones surrounding the foramen magnum and a median bone lying further forward; these are homologous with the occipital bone and parts of the sphenoid in mammals. Finally, the lower jaw is composed of multiple bones, only the most anterior of which (the dentary) is homologous with the mammalian ...
Smilodectes is a genus of adapiform primate that lived in North America during the middle Eocene. [1] It possesses a post-orbital bar and grasping thumbs and toes. Smilodectes has a small cranium size and the foramen magnum was located at the back of the skull, on the occipital bone.
Most notably, it had a small brain size yet was, as shown by the position of the foramen magnum, bipedal. Dart, after hastily freeing the fossil from its matrix, already in January 1925 named the specimen as a new genus and species: Australopithecus africanus. [2]: 284–285
Primates range in size from the 30-gram (1 oz) pygmy mouse lemur to the 200-kilogram (440 lb) mountain gorilla. According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 mya (million years ago), and the oldest known primate is the Late Paleocene Plesiadapis, c. 55–58 mya.
The cranium includes the face, much of the frontal bone, parts of the midvault and the base anterior to the foramen magnum. The cranial length, width and height are 21 cm (8.3 in), 15.87 cm (6.2 in) and 19.05 cm (7.5 in) respectively.