LampreysPetromyzonHagfishesFishesSuperior ColliculiPhysiology, ComparativeVena Cava, SuperiorSpinal CordVertebratesSwimmingMesenteric Artery, SuperiorReticular FormationPhylogenyPyrrolidonecarboxylic AcidMolecular Sequence DataLocomotionChordata, NonvertebrateSuperior Vena Cava SyndromeBiological Evolution