Small to medium-sized tree. Bark dark brown to almost black, deeply fissured in older specimens. Thorns in pairs, straight, often typically pointing backwards. Leaves compound with 4-8 pinnae. Flowers in spherical heads on the new growth, yellow. Pods distinctive, constricted between the seeds, green when young, turning black when ripe, indehiscent. Old pods often still on the tree when the new pods appear.