The respiratory tube is also known in LACM 128319, preserved as cartilaginous tracheal rings. Only the posterior-most end of the tracheal tube – at the end of the neck near the pectoral girdle – is known. The section where the two bronchi split was also preserved in the specimen, but was destroyed during excavation. This is an indication that "Platecarpus" and other mosasaurs had two functional lungs. Snakes, which are closely related to mosasaurs, have only one functional lung with the second often being vestigial or absent. Unlike terrestrial lizards, however, the bronchi separate in front of the area of the forelimbs rather than at the level of the limbs.