A native to Arizona, Texas, and Mexico.  Common name refers to tightly coiled seed pods. (Tornillo) Small tree or large shrub.  Tree is typically multi-stemmed and the bark is fibrous or stringy.  Very open and spreading habit.  The leaves are smaller than other mesquites and are characterized by one pair of pinnae with 5 to 9 pairs of leaflets per pinna.  Each leaflet is 3/8" to 1" in length.  The small 3/4" spines are whitish, slender and appear as pairs along the branches.  The flowers in spring, are bright yellow catkins, 1/4" wide.