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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 central portion of the tympanic part is thin, as it gives rise to the bony inner two-thirds of the ear canal, and in 5 - 20% of skulls the lower surface is perforated by a hole, the foramen of Huschke [1] that opens onto the temporomandibular joint due to incomplete fusion of the anterior and posterior prominences during development.
The evolution of the mammalian middle ear appears to have occurred in two steps. A partial middle ear formed by the departure of postdentary bones from the dentary, and happened independently in the ancestors of monotremes and therians. The second step was the transition to a definite mammalian middle ear, and evolved independently at least ...
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 ...
Structurally, the endocranium consists of a boxlike shape, open at the top. The posterior margin exhibit the foramen magnum, an opening for the spinal cord.The floor of the endocranium has several paired openings for the cranial nerves, and the anterior margin holds a spongy construction, allowing for the external nasal nerves to pass through. [2]
The P. robustus hand is consistent with a humanlike precision grip which would have made possible the production or usage of tools requiring greater motor functions than non-human primate tools. [46] The femur, as in P. boisei and H. habilis, is flattened anteroposteriorly (on the front and back side).
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.