Durian is a simple dry fruit that is classified under the dehiscent category. Dry dehiscent fruits split open when ripe, scattering the seeds away. The dehiscent category includes follicle, legume and capsule. Follicle forms from an ovary with one carpel and splits open on only one side. Legume also forms from an ovary with one carpel and splits open on two sides.
Capsule comes from an ovary where the carpels have fused and splits in various ways.
Durian is a capsule splitting into 4-5 parts at maturity.