Complex sentence: Some are large dogs of approximately 70 lb (32 kg), while others are as small as 40 lb (18 kg); some have natural bobtails and others have long, narrow, short-furred tails.
Split into simpler sentences: Some are large dogs of approximately 70 lb (32 kg), while others are as small as 40 lb (18 kg). Some have natural bobtails and others have long, narrow, short-furred tails.