A way a lone a last a loved a long the riverrun, past Eve and Adam's, from swerve of shore to bend of bay,
brings us by a commodius vicus of recirculation back to Howth Castle and Environs.
All dolphins can hold their breath underwater for quite a long time.
All dolphins are mammals.
Therefore, all mammals can hold their breath underwater for quite a long time.
You see the problem?
It would be true, however, if the second statement read "all mammals are dolphins".
Similar "logic" has been applied to what you said.