Australopithecus anamensis -- KNM-KP 271

Australopithecus anamensis -- KNM-KP 271

This 4 million-year-old left distal humerus was the first Australopithecus anamensis specimen recovered.

Bryan Patterson

KNM-KP 271

Kenya

Kanapoi

1965

4 million years ago

The biostratigraphy of the sequence in which it was found. Later confirmed with ⁴⁰Ar/³⁹Ar dating of the volcanic ash layer.

When this specimen, the distal end of a left humerus, was first discovered, it could not be put into a specific genus, either Homo or Australopithecus, with any degree of certainity because it had morphological overlap with both genuses. However, during a later examination, it was found that the olcranon fossa, the depression in the posterior distal humerus where the ulna articulates with the humerus to form the elbow joint, is rather shallow, like the fossa in anatomically modern Homo sapiens. But rather than being classified as a member of genus Homo, the fact that this specimen was found in a sedimentary layer associated with other known Au. anamensis remains suggests that this distal humerus also belongs to an Australopithesus anamensis. 

Johanson, Donald, and Blake Edgar. From Lucy to Language. New York, Nevraumont Publishing Company, 2006, pp. 129-30

Conroy, Glenn C., and Herman Pontzer. Reconstructing Human Origins: A Modern Synthesis. 3rd ed., New York & London, W. W. Norton & Company, Inc., 2012, pp. 238-40.

Hefner, Joseph. "Australopithecus anamensis." Michigan State University, 23 Feb. 2012, East Lansing.

Image from:
McCarthy, Eugene. "Australopithecus anamensis." Macroevolution.net, www.macroevolution.net/australopithecus-anamensis.html. Accessed 13 Apr. 2017.