Gracile and Robust Morphologies

The australopithecines are usually separated into two morphological types on the basis of their body build:

• gracile forms, notably Australopithecus afarensis, A. africanus;
• robust forms, notably A. robustus, A. boisei, A. aethiopicus.

Though probably little different in overall body weight, gracile and robust forms must have looked very different in stature and facial appearance.

Some palaeontologists prefer to classify the robust forms as Paranthropus, and there is disagreement overspecies names and over the actual number of species that there were.

Some investigators (= "splitters") prefer to classify similar fossils into many species, others (= "lumpers") group many superficially-similar fossils together as one species.

The picture is complicated by nomenclature changes - i.e. the same fossil may be given a new or different name.

See [Wood & Chamberlain 1986] , [Boyd & Silk 1997] (pp 362-373) for further discussion.

Changes of Nomenclature

Beware of name changes. For example, the earliest known hominid was once thought to be a Miocene genus called Ramapithecus.

As more specimens came to light it became clear, not only that Ramapithecus was not an hominid, but also that it was essentially the same taxon as Sivapithecus (shown here), a Miocene ape.

So the two taxa were merged, and because Sivapithecus was older than Ramapithecus, its name took precedence.

As a consequence, Ramapithecus rarely appears these days in accounts of human origins; see [Boyd & Silk 1997] (pp 337-339).

As a further example, Australopithecus robustus was originally known as Paranthropus robustus and Austraplopithecus ramidus has recently been renamed Ardipithecus ramidus.