Australopithecus anamensis -- KNM-KP 271

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Australopithecus anamensis -- KNM-KP 271


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

Fossil Item Type Metadata


Bryan Patterson

Specimen Name/Nickname

KNM-KP 271

Location (Country)


Site (Name)


Discovery Date


Specimen/Species Time Range

4 million years ago

Dating Method

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

Specimen Data (Morphology)

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


KNM-KP 271
Date Added
April 7, 2017
Item Type
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“Australopithecus anamensis -- KNM-KP 271,” Hominid Fossil Repository, accessed August 17, 2022,