Paranthropus aethiopicus

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Paranthropus aethiopicus
Temporal range:
Ma
↓
Reconstruction of KNM WT 17000
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Genus: †Paranthropus
Species:
†P. aethiopicus
Binomial name
†Paranthropus aethiopicus
Arambourg and Coppens, 1968
Synonyms
  • Paraustralopithecus aethiopicus
    Arambourg and Coppens, 1968
  • Australopithecus aethiopicus
    preoccupied
    )
  • Australopithecus walkeri
    Ferguson, 1989

Paranthropus aethiopicus is an

sensu stricto
("in the strict sense") can be used to respectively include and exclude P. aethiopicus from P. boisei.

Like other Paranthropus, P. aethiopicus had a tall face, thick palate, and especially enlarged cheek teeth. However, likely due to its archaicness, it also diverges from other Paranthropus, with some aspects resembling the much earlier A. afarensis. P. aethiopicus is known primarily by the skull KNM WT 17000 from Koobi Fora, Lake Turkana, Kenya, as well as some jawbones from Koobi Fora; the Shungura Formation, Ethiopia; and Laetoli, Kenya. These locations featured bushland to open woodland landscapes with edaphic (water-logged) grasslands.

Taxonomy

Research history

Locations of P. aethiopicus discoveries

In 1968, French palaeontologist Camille Arambourg and Breton anthropologist Yves Coppens described "Paraustralopithecus aethiopicus" based on a toothless mandible (Omo 18) from the Shungura Formation, Ethiopia. The name aethiopicus refers to Ethiopia.[2] In 1976, American anthropologist Francis Clark Howell and Coppens reclassified it as A. africanus.[3]

In 1985, the skull KNM WT 17000 dating to 2.5 million years ago was reported from Koobi Fora, Lake Turkana, Kenya, by anthropologists Alan Walker and Richard Leakey. A partial jawbone from a different individual, KNM-WT 16005, was also discovered. They clearly belonged to a robust australopithecine.[4] By this point in time, much younger robust australopithecines had been reported from South Africa (robustus) and East Africa (boisei), and been variously assigned to either Australopithecus or a unique genus Paranthropus.[5] Walker and Leakey assigned KNM WT 17000 to the boisei clade. They noted several anatomical differences, but were unsure if this stemmed from the specimens' archaicness or represented the normal range of variation for the species. If the former, they recommended classifying them and similar specimens into a different species, aethiopicus (and recommended that Paraustralopithecus be invalid). The discovery of these archaic specimens overturned previous postulations that P. robustus was the ancestor of the much more robust P. boisei (a hypothesis notably argued by palaeoanthropologist Yoel Rak [de] in 1985) by establishing the boisei lineage as beginning long before robustus had existed.[4]

In 1989, palaeoartist Walter Ferguson recommended KNM WT 17000 be classified into a different species, walkeri, because the holotype of aethiopicus comprised only the jawbone and KNM WT 17000 preserves no jaw elements.[3] Ferguson's classification is almost universally ignored,[6] and is considered to be synonymous with P. aethiopicus.[7]

Several more lower and upper jaw specimens have been unearthed in the Shungura Formation,[5]: 112–113  including a juvenile specimen, L338y-6.[8] In 2002, a 2.7–2.5 Ma maxilla, EP 1500, from Laetoli, Tanzania, was assigned to P. aethiopicus. Also found was the upper portion of a tibia, but it cannot definitively be associated with EP 1500 and thus with P. aethiopicus.[9]

Classification

The genus Paranthropus (from

sensu stricto ("in the strict sense") can be used to respectively include and exclude P. aethiopicus from P. boisei when discussing the lineage as a whole.[5]
: 106–107 

It is also debated if Paranthropus is a valid natural grouping (

paraphyletic). Because skeletal elements are so limited in these species, their affinities with each other and to other australopithecines is difficult to gauge with accuracy. The jaws are the main argument for monophyly, but such anatomy is strongly influenced by diet and environment, and could in all likelihood have evolved independently in P. boisei and P. robustus. Proponents of monophyly consider P. aethiopicus to be ancestral to the other two species, or closely related to the ancestor. Proponents of paraphyly allocate these three species to the genus Australopithecus as A. boisei, A. aethiopicus, and A. robustus. British geologist Bernard Wood and American palaeoanthropologist William Kimbel are major proponents of monophyly, and against include Walker.[5]
: 117–121 

Monophyly[5]: 119 
Paraphyly[5]: 119 
Monophyly[13]
Three example family trees with P. robustus (note, they are not absolute)

This species, originally named Paraustralopithecus aethiopicus, cannot retain the species epithet aethiopicus if moved to genus Australopithecus because Australopithecus aethiopicus is already a junior synonym of Australopithecus afarensis. Such a classification would have to use the name Australopithecus walkeri for this species. The change of species epithet would also happen in a taxonomy that classifies all hominins as Homo.[14]

Description

Reconstruction of KNM WT 17000, side view (left) and face (right)

Typical of Paranthropus, KNM WT 17000 is heavily built, and the

ramus of the mandible (connecting the lower jaw to the skull), though the hinge's location indicates the ramus would not have been particularly deep (it would have been weaker). This may have produced a less effective bite compared to P. boisei.[8]

Cast of the Peninj Mandible assigned to P. boisei, which is similar to KNM-WT 16005

KNM-WT 16005 is quite similar to the

tooth roots) and large cheek teeth.[4] Nonetheless, the incisors were likely much broader in KNM-WT 16005.[8] KNM-WT 16005 preserved four cheek teeth on the left side: the third premolar measuring 10.7 mm × 13.8 mm (0.42 in × 0.54 in), the fourth premolar measuring 12 mm × 15 mm (0.47 in × 0.59 in), the first molar measuring 15.7 mm × 14.3 mm (0.62 in × 0.56 in), and the second molar measuring 17 mm × 16.7 mm (0.67 in × 0.66 in). The fourth premolar and first molar are a little smaller than those of the Peninj mandible, and the second molar a bit bigger. The KNM-WT 16005 jawbone is smaller than what KNM WT 17000 would have had.[4]

Many of these P. aethiopicus features are shared with the early A. afarensis, further reiterating the species' archaicness.[4][8]

Palaeoecology

In general, Paranthropus are thought to have been generalist feeders, with the heavily built skull becoming important when chewing less desirable, lower quality foods in times of famine. Unlike P. boisei which generally is found in the context of closed, wet environments, P. aethiopicus seems to have inhabited bushland to open woodland habitats around edaphic (water-logged) grasslands.[5]: 121  Around 2.5 million years ago, at the Pliocene/Pleistocene border, the Omo–Turkana Basin featured a mix of forests, woodlands, grasslands, and bushlands, though grasslands appear to have been expanding through the Early Pleistocene. Homo seems to have entered the region 2.5–2.4 million years ago.[15]

See also

References

  1. ^ or Australopithecus walkeri as the former combination is preoccupied by a junior synonym of Australopithecus afarensis
  2. ^ Arambourg, C.; Coppens, Y. (1968). "Sur la decouverte dans le Pleistocene inferieur de la valle de l'Omo (Ethiopie) d'une mandibule d'Australopithecien" [On the discovery in the Lower Pleistocene Omo Valley (Ethiopia) of an Australopithecine Mandible]. Comptes Rendus des Séances de l'Académie des Sciences (in French). 265: 589–590.
  3. ^
    S2CID 28642451
    .
  4. ^
    S2CID 4270200
    .
  5. ^
    PMID 18046746
    .
  6. ISBN 978-1-4443-4247-5
    .
  7. ISBN 978-0-385-46792-6
    .
  8. ^
    PMID 7802091
    .
  9. ^ Harrison, T. (2002). "The first record of fossil hominins from the Ndolanya Beds, Laetoli, Tanzania". American Journal of Physical Anthropology. 32: 83.
  10. ^ "Paranthropus". Merriam–Webster Dictionary. Retrieved 20 June 2020.
  11. S2CID 53574805
    .
  12. PMID 31182201
    .
  13. ^ McNulty, K. P. (2016). "Hominin Taxonomy and Phylogeny: What's In A Name?". Nature Education Knowledge. 7 (1): 2.
  14. PMID 10600324
    .
  15. ISBN 978-1-4020-9980-9
    .

External links
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