Complex sentence: Relative to its small size, the onefin electric ray can deliver an extremely powerful electric shock to defend itself against predators, which include the broadnose sevengill shark ("Notorynchus cepedianus").
Split into simpler sentences: Relative to its small size, the onefin electric ray can deliver an extremely powerful electric shock for defensive purposes. Its known predators include the broadnose sevengill shark ("Notorynchus cepedianus").