Robust Australopithecines

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Robust Australopithecines
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Robust Australopithecines

• Chronology
• Diagnostic Features
• Species
• Paranthropus boisei
• Paranthropus robustus
• Paranthropus aethiopicus

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Genus Australopithecus

• Robust Early Hominids (2.5-1.5 mya)
• Highly specialized features
• Heavy brows
• Large teeth, particularly back
• Large muscle attachment areas
• Jutting lower jaw (prognathism)
• Some from East Africa, Some from South Africa

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Paranthropus boisei
OH 5, "Zinjanthropus", "Nutcracker Man",
Paranthropus boisei Discovered by Mary Leakey
in 1959 at Olduvai Gorge in Tanzania (Leakey
1959). Estimated age is 1.8 million years.
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Paranthropus boisei (KNM-ER 406)
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Diagnostic Features

• The most striking feature of the Paranthropus
  boisei specimens is the degree of megadontia
  (large teeth).
• This species has the absolute largest teeth found
  in any hominid group, with teeth similar in size
  to gorillas (who weigh as much as 10 times as
  much). They are often referred to as hyper-robust
  due to the massive postcanine megadontia.
• Features include
• The face is more vertically set, more
  orthognathic (variability in this trait).
• There is anterior teeth reduction.
• There is a continued increase in postcanine teeth
  size.
• There is a larger cranial capacity (500-550 cc).
• The sagittal crest is on the mid-brain case, not
  the posterior.

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Paranthropus robustus

• The species Paranthropus robustus was first
  discovered and named by the eminent Dr. Robert
  Broom.
• Broom made a habit of buying fossil remains from
  a lime quarry worker, and on a particular visit
  on June 8, 1938, Broom bought a maxillary
  fragment containing a first molar.

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S. Africa-important sites
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P. robustus (TM 1517)
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Diagnostic Features

• The P. robustus remains generally are from three
  sites Swartkrans, Dreimulen, and Kromdraai. By
  far the largest of these sites is Swartkrans.
• One of the major problems with these South
  African sites is dating, but generally, robustus
  remains can be safely placed from 2.0-1.0 myr,
  and possibly even earlier. The dating of these
  sites is crucial to understanding the phylogeny
  of the robust australopithecines, but for now,
  the dates are somewhat in question.

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• The robustus crania are many, but fragmentary,
  with a known cranial capacity for just one
  individual specimen, SK 1585, an endocast with a
  530 cc capacity.
• There is evidence of significant expansion over
  africanus, with an estimated 15 average increase
  in brain size over africanus. The sexual
  dimorphism level of about 20 seems to be
  basically unchanged. In his analysis of SK 1585,
  R. Holloway concluded that robustus shows a
  general trend towards a more modern brain -
  similar to that of boisei - over that of
  africanus.

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Paranthropus robustus
DNH 7, "Eurydice", Paranthropus robustus.
Discovered by André Keyser in 1994 at
the Drimolen cave in South Africa. Estimated age
is between 1.5 and 2.0 million years.
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Drimolen Site

• A new and relatively unknown site in the Rhino
  and Lion Nature Reserve situated about seven
  kilometers north of the famous Sterkfontein
  hominid site.
• Dr Andre Keyser and Dr Lee Berger announced the
  discovery and excavation of the most complete
  skull of an ape-man ever to be scientifically
  described.
• The skull is that of a female Paranthropus
  robustus, also described as a hominid ape-man
  with very large teeth and a dished face.
• This specimen has an intact lower jaw and all its
  teeth preserved.
• A different specimen comprising just a very large
  lower jaw and large teeth is that of a male of
  the same species.
• This larger jaw was discovered just a few
  centimeters from the female skull.

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• The newly discovered female skull and the male
  mandible indicates that the sexes differed more
  markedly from one another than in modern humans
  today.
• This is also the case as in the great apes such
  as the Gorilla and Chimpanzee.
• The Drimolen site has to date yielded 79
  individual specimens and a large variety of
  fossil animal species.

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Drimolen Site
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P. robustus (SK 48)
From Swartkrans, S. Africa
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Swartkrans, S. Africa
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A Plan of the Kromdraai.
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Paranthropus aethiopicus

• The discovery of KNM-WT 17000 (the "Black Skull")
  occurred in 1986, and is an important part of the
  australopithecine puzzle. Very little is known
  about P. aethiopicus, since so few specimens have
  been attributed to the species, but the features
  that are known provide important insights into
  the possible evolutionary history between the
  "robust" and "gracile" australopithecines. In
  general, aethiopicus shows a mixture of both
  primitive and derived features, and dates to a
  time that makes it important in the its placement
  into the hominid phylogenetic tree.

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• The first specimen attributed to this species
  group is a mandible (Omo 18) found in southern
  Ethiopia, west of the Omo River, in 1967.
• This 2.5 million year old mandible was placed
  into a new species by its discoverers, who named
  the species Paranthropus aethiopicus.
• They believed that the specimen deserved a new
  species designation because its V-shaped jaw
  (among other features) distinguished it from the
  robust australopithecus forms known in the area.
  Generally, the discovery and designation was
  ignored by the majority of paleoanthropologists.
• Not until the Black Skull discovery was there
  much interest in the specimen, but once KNM-WT
  17000 was discovered in, interest was renewed in
  the Omo mandible.

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The Black Skull (KNM-WT 17000)
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Diagnostic Features

• The better known aethiopicus specimen is KNM-WT
  17000, a nearly complete skull sans the mandible.
  The specimen is known as the "Black Skull"
  because mineral uptake during fossilization gave
  the specimen a blue-black color.
• The specimen was discovered in a 2.5 myr deposit
  west of Lake Turkana, and through a wrench in
  many evolutionary schemes accepted by many
  researchers.
• The specimen is similar to a male A. afarensis,
  but with a very small cranial capacity (410 cc),
  and an even more powerful nuchal musculature and
  very developed masticatory apparatus.

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Features of the Black Skull

• The well-developed masticatory (chewing) features
  are seen by
• The large palate with a thick roof.
• The broken roots of large rooted (and thus
  probably large crowned) molars and 4th premolar.
• A flat, flaring face.
• The combination of a very small brain and
  enlarged masticatory apparatus leads to the
  development of a well-developed sagittal crest
  that meets the nuchal crest to form a compound
  temporonuchal crest similar to A. afarensis at
  the rear of the vault.
• Large anterior tooth sockets.
• A flattened cranial base.
• A posterior foramen magnum position.
• Extreme facial prognathism (jutting lower
  jaw/face).

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The Black Skull (KNM-WT 17000)
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What happened to robusts?

• Specialized teeth for chewing coarse food in
  grassland/savannah environment.
• Climate change at around 1 mya could have caused
  them to go extinct because they were too
  specialized.
• Extinct lineage.

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