From flat foot to fat foot: structure, ontogeny, function, and evolution of elephant 'sixth toes'
| Autor: | Andrew A. Pitsillides, Cyrille Delmer, Alan Boyde, Thomas B. Hildebrandt, John R. Hutchinson, Charlotte E. Miller |
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| Rok vydání: | 2011 |
| Předmět: |
Plantigrade
Ontogeny Movement Elephants Biology Extant taxon Osteogenesis Foot Joints Forelimb medicine medicine.bone Animals Multidisciplinary Osteology Ossification Foot Fossils Anatomy Toes Biological Evolution Biomechanical Phenomena Hindlimb body regions Cartilage Adipose Tissue Sesamoid bone Foot structure Microscopy Electron Scanning Female medicine.symptom Sesamoid Bones Tomography X-Ray Computed Foot (unit) Locomotion |
| Zdroj: | Science (New York, N.Y.). 334(6063) |
| ISSN: | 1095-9203 |
| Popis: | Several groups of tetrapods have expanded sesamoid (small, tendon-anchoring) bones into digit-like structures ("predigits"), such as pandas' "thumbs." Elephants similarly have expanded structures in the fat pads of their fore- and hindfeet, but for three centuries these have been overlooked as mere cartilaginous curiosities. We show that these are indeed massive sesamoids that employ a patchy mode of ossification of a massive cartilaginous precursor and that the predigits act functionally like digits. Further, we reveal clear osteological correlates of predigit joint articulation with the carpals/tarsals that are visible in fossils. Our survey shows that basal proboscideans were relatively "flat-footed" (plantigrade), whereas early elephantiforms evolved the more derived "tip-toed" (subunguligrade) morphology, including the predigits and fat pad, of extant elephants. Thus, elephants co-opted sesamoid bones into a role as false digits and used them for support as they changed their foot posture. |
| Databáze: | OpenAIRE |
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