The animals of prehistory were massive, but there are definitely some heavyweights that exist today. The longest snake is the reticulated python and it generally reaches lengths of up to 20 feet — though the record is 33 feet. They are usually tame but can be "a jumpy and unpredictable species." They are often kept as pets but can turn out to be too much for their owners (click here for a photo of nine men holding one). Python reticulatis is found in southeast Asia. It is non-venomous, but it could kill a grown man through strangulation.