Australopithecus anamensis

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Australopithecus anamensis All you wanted to
know (sort of)
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• The discovery
• anamensis was discovered in the Kanapoi region of
  East Lake Turkana in 1965 by a Harvard University
  expedition. The first discovery was that of a
  partial left humerus Johanson and Edgar, 1996.
  There were virtually no further discoveries
  associated with this species until the 1990s.
• Meave Leakey and other affiliates of the National
  Museums of Kenya organized a research team for
  the Kanapoi region Coffing, et al, 1994
  prompting the further finds in 1992, including
  one complete lower jaw bone which closely
  resembles that of a common chimpanzee (Pan
  troglodytes) but whose teeth are much more
  similar to those of a human.

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In 2006, a new A. anamensis find was officially
announced, extending the range of A. anamensis
into north east Ethiopia. These new fossils,
sampled from a woodland context, include the
largest hominid canine yet recovered and the
earliest Australopithecus femur.
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Geography The Kanapoi sequence contains strata
which were deposited during an interval between
4.17 and 3.5 million years ago. The lower
level's location, between two layers of volcanic
ash (dated to 4.17 and 4.12 million years,
respectively), allows us to safely assign a date
of 4.1 million years. The lower level was
deposited at a time when an ancient lake, Lake
Lonyumun, dominated the landscape. Though most
of the Australopithecus anamensis specimens were
taken from this level, the assemblage does not
include any postcranial material, and mainly
consists of elements of this hominid's dentition.
Fossils from Allia Bay were obtained either
within or below the Moiti Tuff, which is 3.9
million years old. Sedimentation occurred within
the proximity of an ancient meandering river
called the Proto-Omo.
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Anatomical differences between Ar. ramidus and A.
anamensis -Both species have retained
ape-like crania and dentition. -A. anamensis can
be distinguished from Ar. ramidis by the
absolutely and relatively thicker tooth
enamel. -molars are buccolingually expanded,
producing a smaller length to breadth
ratio. (length breadth is 1.49 in A. ramidus,
1.4 in A. anamensis, and 1.2 in A. afarensis)
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Anatomical differences between A. anamensis and
A. afarensis -Both share a shallow
palate -articular surface (which joins with the
talus) faces inferiorly (rather than
antero-inferiorly, which occurs in quadrupedal
apes). Additionally, the proximal articular
condyles (which join with the femur to form the
knee joint) are deeply concave, broad in the
antero-posterior plane, and equal in size.
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Point of Interest The tibia, and the humerus of
A. anamensis may be more similar to those from
members of the genus Homo than they are to
Australopithecus afarensis Andrews, 1995. This
has not been decisively shown, but, if true,
would bring up a very interesting possibility.
It may very well be possible that we are more
closely related to this 4 million year-old
hominid than we are to the widely successful
later hominid - Australopithecus afarensis.
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