Sauriurae (meaning "lizard tails" in Greek) is a now-deprecated subclass of birds created by Ernst Haeckel in 1866.
The distinction Haeckel referred to in this name is that Archaeopteryx possesses a long, reptile-like tail, while all other birds known to him had short tails with few vertebrae, fused at the end into a pygostyle.
[1] The unit was not much referred to, and when Hans Friedrich Gadow in 1893 erected Archaeornithes for basically the same fossils, this became the common name for the early reptile-like grade of birds.
Ji Qiang and Larry Martin have continued to refer to the Sauriurae as a valid natural group.
[2] However, researchers like Jacques Gauthier (2001)[3] and Julia Clarke (2002)[4] have found that fossils found after Haeckel's time have bridged the gap between long and short-tailed Avialae.