ballistids

Ballistids are a hypothetical group of birds that are thought to have played a key role in the evolution of modern birds. The term "ballistid" was first coined by Russian zoologist Gregory Altsheler in 1931 and is derived from the Greek words "ballimos" meaning "thrust" and "itis" meaning "-form" or "-type".

Ballistids are believed to have been aerodynamically advanced birds that lived during the late Jurassic period, around 155-145 million years ago. Fossil remains of these birds have been found in the Gobi Desert in Mongolia and in North America. These remains include impressions of feathers and wishbone-shaped skeletons.

One of the most notable characteristics of ballistids is the presence of asymmetrical wings, with one wing significantly larger than the other. This unique wing arrangement is thought to have allowed ballistids to make sharp, diving turns, or "ballistic" maneuvers, which earned them their name.

Ballistids are often considered to be transitional forms between theropod dinosaurs and modern birds, and their unusual wing arrangement is thought to have been an early adaptation for powered flight. However, the exact relationships between ballistids and other groups of birds and dinosaurs are still the subject of ongoing research and debate.

Despite their potentially significant role in the evolution of modern birds, ballistids are still a poorly understood group, and many questions remain about their biology and behavior. Further study of ballistid fossils and their aerodynamic characteristics may eventually shed more light on the history of bird evolution.