Penguins are a family of medium to large-sized aquatic birds that live in the Southern Hemisphere.
Distribution & Fossil evidence
The first members of the Spheniscidae-family existed just after the K-Pg extinction event. These basal members weren't as well-adapted to aquatic life as modern day penguins. They swam more with their feet instead of their wings, but they were already flightless.
There are several genuses of extinct penguins known, of which the basal members could grow up to enormous sizes! Anthropornis, for example, could grow up to 1.8 meters in height!