Paranthropus Robustus - Morphology

Morphology

Typical of robust australopithecines, P. robustus had a head shaped a bit like a gorilla's with a more massive built jaw and teeth in comparison to hominins within the Homo lineage. The sagittal crest that runs from the top of the skull acts as an anchor for large chewing muscles. The DNH 7 skull of Paranthropus robustus, "Eurydice", was discovered in 1994 at the Drimolen Cave in Southern Africa by Andre Keyser, and is dated to 2.3 million years old, possibly belonging to a female.

The teeth of these primates were larger and thicker than any gracile australopithecine found, due to the morphology differences Broom originally designated his find as Australopithecus robustus. On the skull, a bony ridge is located above from the front to back indicating where the jaw muscles joined. P. robustus males may have stood only 1.2m (4 feet) tall and weighed 54 kg (120 lb) while females stood just under 1 meter (3 feet 2 inches) tall and weighed only 40 kg (90 lb), indicating a large sexual dimorphism. The teeth found on P. robustus are almost as large as those of P. boisei.

Broom analyzed his findings carefully and noted the differences in the molar teeth size which resembled a gorilla's a bit more than a human's. Other P. robustus remains have been found in Southern Africa. The average brain size of P. robustus measured to only 410 and 530 cc, about as large as a chimpanzee's. Some have argued that P robustus had a diet of hard gritty foods such as nuts and tubers since they lived in open woodland and savanna. More recent research suggests that this taxon was more of a dietary generalist, and others have argued that they principally consumed hard and gritty resources as fallback foods only during time of nutritional stress.

A 2011 study using ratios of strontium isotopes in teeth suggested that Australopithecus africanus and P. robustus groups in southern Africa were patrilocal: females tended to settle farther from their region of birth than males did.