diencephalon morphology trait subthalamus morphology trait Any measurable or observable characteristic related to the shape, structure, color, or pattern of the anterior part of the diencephalon that lies between the thalamus, hypothalamus, and tegmentum of the mesencephalon, including subthalamic nucleus, zona incerta, the fields of Forel, and the nucleus of ansa lenticularis. Trait.ontology VT:0000834 ventral thalamus morphology trait