Simplify the following text for a Grade 8 native English-speaking person.
Original: The Seven-arm Octopus ( Haliphron atlanticus ) is the largest known species of octopus based on scientific records , with a total estimated length of 4 m and weight of 75 kg .
Simplified: The Seven-arm Octopus ( Haliphron atlanticus ) is the biggest known octopus , growing up to 4 m and weight of 75 kg .