Developmental identity versus typology: Lucy has only four sacral segments
| Autor: | C. Owen Lovejoy, Allison L Machnicki, Philip L. Reno |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Primates
musculoskeletal diseases 0301 basic medicine Sacrum Hominidae Context (language use) Biology Models Biological Fossilization Anthropology Physical 03 medical and health sciences Sacral Vertebra medicine Animals Hox gene Fossils Anatomy musculoskeletal system biology.organism_classification Biological Evolution body regions 030104 developmental biology medicine.anatomical_structure Australopithecus Anthropology Female Vertebral column |
| Zdroj: | American Journal of Physical Anthropology. 160:729-739 |
| ISSN: | 1096-8644 0002-9483 |
| Popis: | Objectives Both interspecific and intraspecific variation in vertebral counts reflect the action of patterning control mechanisms such as Hox. The preserved A.L. 288-1 (“Lucy”) sacrum contains five fused elements. However, the transverse processes of the most caudal element do not contact those of the segment immediately craniad to it, leaving incomplete sacral foramina on both sides. This conforms to the traditional definition of four-segmented sacra, which are very rare in humans and African apes. It was recently suggested that fossilization damage precludes interpretation of this specimen and that additional sacral-like features of its last segment (e.g., the extent of the sacral hiatus) suggest a general Australopithecus pattern of five sacral vertebrae. Methods We provide updated descriptions of the original Lucy sacrum. We evaluate sacral/coccygeal variation in a large sample of extant hominoids and place it within the context of developmental variation in the mammalian vertebral column. Results We report that fossilization damage did not shorten the transverse processes of the fifth segment of Lucy's sacrum. In addition, we find that the extent of the sacral hiatus is too variable in apes and hominids1 to provide meaningful information on segment identity. Most importantly, a combination of sacral and coccygeal features is to be expected in vertebrae at regional boundaries. Discussion The sacral/caudal boundary appears to be displaced cranially in early hominids relative to extant African apes and humans, a condition consistent with the likely ancestral condition for Miocene hominoids. While not definitive in itself, a four-segmented sacrum accords well with the “long-back” model for the Pan/Homo last common ancestor. Am J Phys Anthropol, 2016. © 2016 Wiley Periodicals, Inc. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text