An endostyle's a longitudinal ciliated groove on the ventral wall of the pharynx which produces mucus to gather food particles. It's found in urochordates and cephalochordates, and in the larvae of lampreys. It aids in transporting food to the esophagus. It's also called the hypopharyngeal groove. The endostyle in larval lampreys (ammocetes) metamorphoses into the thyroid gland in adults, and's regarded as being homologous to the thyroid gland in vertebrates. However, Dumont, et al. question whe… (More on Endostyle)