Giants of the sky

During the last 120 million years giant flying animals have been a rule rather than an exception. During the Mesozoic we had giant pterosaurs and later we had giant birds.

Here is an article from Scientific America about one such bird Pelagornis sandersi,, which could have a wingspan of around 7 meters.

The discovery of P. sandersi—a titan among what were already considered to be exceptionally large birds—raises the question of why giant size evolved in flying avians. Gigantism is not universally advantageous in biology. Big animals need more food than small ones, they may require larger areas for nesting and they tend to have smaller population sizes than modestly proportioned species. Yet despite those drawbacks, multiple successful lineages of giant fliers have evolved over the course of the earth's history. In fact, the lack of truly enormous fliers today is the exception to the rule: giant flying animals darkened the skies for most of the past 120 million years.

Bizarre, Giant Birds Once Ruled the Skies