In the "Encyclopedia of Native American Bows, Arrows, and Quivers Volume 2" by Alley & Hamm, they describe three different Navajo bows. The first is a split limb with a rounded back and flattened belly that is 39.5 inches long. They do not mention what kind of wood it is.
The second is 42.5 inches long and is a sinew-backed bow but again, there is no mention of what type of wood it is made from.
The third is 47 inches long, sinew-backed, and was made from Mesquite.
There are also some depictions of painting schemes, arrows, and beautiful quiver and bow case made from mountain lion skin with decorative beading.
Hope that helps.
--Steve