They range from tiny 7.5 cm (3-inch) flycatchers to the large common raven, which can reach nearly 120 cm (46 inches) in length. Evolutionary Success

The order is primarily divided into two main groups based on the anatomy of their syrinx muscles:

Passerines are considered the most highly evolved avian group, having undergone a massive evolutionary radiation during the Paleogene period. Researchers from Nature note that they originated in the Southern Hemisphere (Gondwana) before spreading to every continent except Antarctica. Classification: Oscines vs. Suboscines