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RE: Development question
>>>>> Kris said:
> I need to figure out how to explain the developmental aspect of the avian
> furcula. The wishbone is a non-endocartilarinous element that develops as
> a connective tissue precursor with no cartilage present. However, our
> clavicle does develop with both a cartilaginous and connective tissue
> precursors. Does this imply the same for theropods and birds? I do not
> know. Can anyone help me out?
According to "Essentials of Gross Anatomy" by Jack Stern:
"The clavicle is the sole membrane bone of the shoulder girdle in mammals.
Its ends are preformed in cartilage (and in fact the medial end develops an
epiphyseal ossification center within its cartilage), but this is considered
a secondary development acquired in mammalian evolution."
This would imply that the bird clavicle is strictly an intramembranous
ossification. Unfortunately, as this is a textbook produced for med student
consumption, there is no citation on this factoid. But, at least it's a
Andy "Studying for His Oral Exams" Farke