is it found in vertebrates only?
The epiglottis is present in mammals, including land mammals and cetaceans, also as a cartilaginous structure. Like in humans, it functions to prevent entry of food into the trachea during swallowing.
Epiglottis
The epiglottis is present in mammals, including land mammals and cetaceans, also as a cartilaginous structure. Like in humans, it functions to prevent entry of food into the trachea during swallowing. 
what is the purpose of the epiglottis in the respiratory system of humans It prevents food from entering the windpipe and the lungs what are its variations? A high-rising epiglottis is a normal anatomical variation, visible during an examination of the mouth. It does not cause any serious problem apart from maybe a mild sensation of a foreign body in the throat. does it play any role in speaking? In some languages, the epiglottis is used to produce epiglottal consonant speech sounds, though this sound-type is rather rare. how does it affect swallowing? During swallowing, the epiglottis bends backwards, folding over the entrance to the trachea, and preventing food from going into it. what is the structure of this organ which is covered during swallowing? It is shaped like a leaf of purslane and has a free upper part that rests behind the tongue, and a lower stalk can it be replaced? UNANSWERABLE which are the disorders related to it? Inflammation of the epiglottis is known as epiglottitis. Epiglottitis is mainly caused by "Haemophilus influenzae". A person with epiglottitis may have a fever, sore throat, difficulty swallowing, and difficulty breathing.
wiki:13284292
Epiglottis [SEP] Other animals
The epiglottis is present in mammals, including land mammals and cetaceans, also as a cartilaginous structure. Like in humans, it functions to prevent entry of food into the trachea during swallowing. The position of the larynx is flat in mice and other rodents, including rabbits. For this reason, because the epiglottis is located behind the soft palate in rabbits, they are obligate nose breathers, as are mice and other rodents. In rodents and mice, there is a unique pouch in front of the epiglottis, and the epiglottis is commonly injured by inhaled substances, particularly at the transition zone between the flattened and cuboidal epithelium.