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Photo#386077
Gall?  Moldy marshmallow?  What? - Andricus

Gall? Moldy marshmallow? What? - Andricus
Molino Basin, Santa Catalina Mountains, ~4,000 ft. elev., Pima County, Arizona, USA
April 13, 2010
Size: large marshmallow
Found this on the ground, so not sure what tree it fell off of, if it even is a gall. Oaks are the dominant tree at this site, however.

Moved
Moved from ID Request. ID via comparison to an image of a remarkably similar gall caused by Andricus frunessae. I could still be wrong, of course.

Oak?
I'll go out on a limb to suggest that this is the twig of an oak; note the ridged surface near the tip and the clustered buds at the tip (well, the terminal bud and the bud scars subtending where the two flanking buds were before they fell off this dead twig). A characteristic tree of the oak woodlands in this region is Emory Oak (Quercus emoryi); for comparison, here (scroll down to near bottom of page) is an image of an Emory Oak twig in winter (leafless) condition (keeping in mind that Eric's image is of a dead, weathered twig while the webpage illustrates a live twig).

Twig
Do you have a clearer shot of the tip of the twig? Someone knowledgeable about SW plants may be able to make sense of the buds and leaf scars. If it is an oak, it would be some kind of cynipid gall (and there are a lot of undescribed ones in your area); if not, likely a cecidomyiid. Can't completely rule out the moldy marshmallow hypothesis though.

 
:-)
I was mostly joking about the marshmallow. The object was too heavy to have been one.