Editing Forelimb (section)

==== Opposable thumbs ====
Modern humans are unique in the musculature of the forearm and hand, though opposable thumbs or structures like them have arisen in a few animals.

In dinosaurs, a primitive autonomization of the first [[carpometacarpal joint]] (CMC) may have occurred. In primates, a real differentiation appeared perhaps 70 mya, while the shape of the human thumb CMC finally appears about 5 mya.

* [[Primate]]s fall into one of four groups:<ref>{{Cite book|title=Primate anatomy : an introduction|last=Ankel-Simons, Friderun.|date=2007|publisher=Elsevier Academic Press|isbn=978-0-08-046911-9|edition=3rd|location=Amsterdam|oclc=437597677}}</ref>
** Nonopposable thumbs: [[tarsier]]s and [[marmoset]]s
** Pseudo-opposable thumbs: all [[strepsirrhine]]s and [[Cebidae]]
** Opposable thumbs: [[Old World monkey]]s and all [[Hominidae|great apes]]
** Opposable with comparatively long thumbs: [[gibbon]]s (or lesser apes)

Pandas have evolved pseudo-opposable thumbs by extension of the [[sesamoid bone]], which is not a true digit.<ref>{{Cite journal|last1=Salesa|first1=Manuel J.|last2=Antón|first2=Mauricio|last3=Peigné|first3=Stéphane|last4=Morales|first4=Jorge|date=2006-01-10|title=Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas|journal=Proceedings of the National Academy of Sciences|language=en|volume=103|issue=2|pages=379–382|doi=10.1073/pnas.0504899102|issn=0027-8424|pmid=16387860|pmc=1326154|bibcode=2006PNAS..103..379S|doi-access=free}}</ref>