All of the following structures are derivatives of the the secondary vesicle called diencephalon, EXCEPT:
The derivatives of diencephalon are subthalamus, thalamus, hypothalamus, epithalamus and third ventricle. Derivatives of secondary vesicles:Telencephalon: cerebral hemispheres, lateral ventriclesMesencephalon: midbrain, cerebral aqueductMetencephalon: pons, cerebellum, upper aspect of fouh ventricleMyelencephalon: lower aspect of fouh ventricle, medulla oblongataRef: Atlas of Neuroradiologic Embryology, Anatomy, and Variants edited by J. Randy Jinkins page 9
Thalamus
Subthalamus
Hypothalamus
Cerebral aqueduct