A genus of extinct hominins dating ~4 mya to 2 mya, and found primarily in eastern and southern Africa. Homo may have evolved from a late australopithecine. Australopithecine brain size is ~35% of the size of the modern human brain.  Most species were short in stature, although sexual dimorphism was pronounced. Some examples of australopithecines:

A. anamenis:  Kenya and Ethiopia. ~4 mya. 
A. afarensis: Eastern Africa. Most famous example is “Lucy.” ~3.9 mya to 2.9 mya. 
A. bahrelghazali: Central Africa.  ~3.6 mya
A. africanus: Southern Africa. ~3.3 mya to 2.1 mya.
A. garhi: Ethiopia. Possible transitional stage between Australopithecus and Homo. ~2.5 mya. 
A. boisei: East Africa. Robust australopithecine. There is debate as to which genus they belong, Australopithecus or Paranthropus. ~2.4 to 1.4 mya.
A. sediba: South Africa. Possible transitional stage between Australopithecus and Homo. ~2 mya.