Penguins (Spheniscidae) are a family of birds, the only one in the order Sphenisciformes. They are non-flying seabirds that are distributed almost exclusively in the southern hemisphere, with the exception of the Galapagos penguin (Spheniscus mendiculus). The name of the order comes from the word spheniscus , literally "wedge", referring to its hydrodynamic shape when swimming.