Deinonychosauria

Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica, with fossilized teeth giving credence to the possibility that they inhabited Australia as well. This group of dinosaurs are known for their sickle-shaped toe claws and features in the shoulder bones. Deinonychosauria is commonly defined as all dinosaurs more closely related to dromaeosaurids (such as Deinonychus antirrhopus) than to birds (such as Passer domesticus). It traditionally includes the families Dromaeosauridae and Troodontidae, which each possess enlarged "sickle claws". However, troodontids may instead be closer to birds than to dromaeosaurids, so they would lie outside Deinonychosauria under that hypothesis. This would also render Deinonychosauria equivalent to Dromaeosauridae, under a broad definition of the family. As the structure of the paravian family is still undergoing debate, the components of Deinonychosauria is unstable beyond dromaeosaurids. In 1866 Ernst Haeckel created the now-deprecated subclass of birds known as Sauriurae (meaning "lizard tails" in Greek). It was intended to include Archaeopteryx and distinguish it from all other birds then known, which he grouped in the sister-group Ornithurae ("bird tails"). 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. 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. This was followed by Alfred Romer (1933) and subsequent authors through most of the 20th century. According to Romer, the Archaeornithes are characterised by having clawed wings, a reptilian style ribcage without a large carina and the presence of a long, bony tail.