Post-orbital constriction

Post-orbital constriction for various hominids[1]
Increased constriction
Gorilla0.57
P. walkeri
(KNM-WT 17000)		0.57
P. boisei
(KNM-ER 406)		0.57
Intermediate
Dryopithecus
(RUD 77)		0.73
Sahelanthropus
(TM 266-01-060-1)		0.59
Australopithecus0.66
P. robustus0.70
Homo habilis
(OH 24, KNM-ER 1813)		0.72
K. rudolfensis0.70
H. ergaster0.75
Pongo0.66
Pan0.70
Reduced constriction
Praeanthropus0.80
Absolutely reduced constriction
Homo sapiens0.92

In physical anthropology, post-orbital constriction, often referred to as the post-orbital constriction index, is a narrowing of the cranium (skull) just behind the eye sockets (the orbits, hence the name), in primates — including primitive hominids. This constriction is very noticeable in non-human primates, slightly less so in Australopithecines, even less in Homo erectus and the most primitive Homo sapiens.[1] The post-orbital constriction index of archaic Homo species begins to fall within the range of modern Homo sapiens during the Mid-Pleistocene era.[2] In a departure from Homo erectus, Homo sapiens manifests a reduced post-orbital constriction due to increase in cranial capacity (about 1,350 cc), accompanied by higher cranial vaults. It completely disappears in modern Homo sapiens.[3] Thus, it is a useful, quantifiable measure of how far along the evolutionary path a hominid fossil might be placed.

In species such as baboons and African great apes, an increase in the available capacity of the infratemporal fossa is simultaneously accompanied by a constriction in the sagittal plane.[4] As such, the anterior and posterior portions of the anterior temporalis muscle are inversely correlated in size, with the anterior being larger.[4] Although the temporalis muscle is used for chewing, there is no evidence that the supraorbital structure of primates is dependent upon their respective chewing habits or dietary preferences.[5]

Post-orbital constriction is defined by either a ratio of minimum frontal breadth (MFB) behind the supraorbital torus divided by maximum upper facial breadth (bifrontomalare temporale, BFM) or as the maximum width behind the orbit of the skull.[1][6][7]

See also

Notes

  1. 1 2 3 Cameron 2004, pp 304-305
  2. ↑ Rightmire, G. Philip (2008-02-22). "Homo in the middle pleistocene: Hypodigms, variation, and species recognition". Evolutionary Anthropology: Issues, News, and Reviews. 17 (1): 8–21. doi:10.1002/evan.20160. ISSN 1060-1538.
  3. ↑ "Archaic Homo sapiens | Learn Science at Scitable". www.nature.com. Retrieved 2018-08-09.
  4. 1 2 KUBO, DAISUKE; KONO, REIKO T.; SUWA, GEN (2012). "Endocranial proportions and postorbital morphology of the Minatogawa I and IV Late Pleistocene Homo sapiens crania from Okinawa Island, Japan". Anthropological Science. 120 (2): 179–194. doi:10.1537/ase.110804. ISSN 0918-7960.
  5. ↑ Picq, Pascal (1994). "Craniofacial size and proportions and the functional significance of the supraorbital region in primates". Zeitschrift für Morphologie und Anthropologie. 80 (1): 51–63.
  6. ↑ Kimbel, William H.; White, Tim D.; Johanson, Donald C. (1984-08). "Cranial morphology ofAustralopithecus afarensis: A comparative study based on a composite reconstruction of the adult skull". American Journal of Physical Anthropology (in French). 64 (4): 337–388. doi:10.1002/ajpa.1330640403. ISSN 0002-9483. Check date values in: |date= (help)
  7. ↑ Monson, Tesla; F. Brasil, Marianne; J. Stratford, Dominic; Hlusko, Leslea (2017-02-14). "Patterns of craniofacial variation and taxonomic diversity in the South African Cercopithecidae fossil record". Palaeontologia Electronica. 20.1.7A: 1–20. doi:10.26879/690.

References

  • Cameron, David W.; Groves, Colin P. (2004). Bones, stones, and molecules: "out of Africa" and human origins. Academic Press. ISBN 0-12-156933-0.


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.