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Scansoriopterygidae

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Scansoriopterygidae is a unique family of extinct dinosaurs. Their name means "climbing wings."

Size comparison of scansoriopterygid dinosaurs
Size comparison of scansoriopterygid dinosaurs

These small animals belonged to a group called maniraptorans. Scientists believe they were arboreal or semi-arboreal. This means they lived in trees or spent much of their time there. They are important because they show how climbing might lead to gliding.

Yi qi restoration
Yi qi restoration

These dinosaurs had very specific body parts for life in the trees. Most theropod dinosaurs have a second finger that is the longest. In scansoriopterygids, the third finger is extremely long. This long finger helped them grip branches. Some species, like *Yi qi* and *Ambopteryx*, also had a styliform bone. This is a long bone growing from the wrist. It worked with the long finger to support a skin membrane. This membrane was used for gliding, much like a bat.

Yi qi restoration
Yi qi restoration

Scansoriopterygids were among the smallest non-avian dinosaurs ever found. Their sizes varied depending on the species and age. Juvenile *Scansoriopteryx* specimens were only about the size of house sparrows. The subadult *Epidexipteryx* was roughly the size of a pigeon.

Size comparison of scansoriopterygid dinosaurs
Size comparison of scansoriopterygid dinosaurs

These small sizes helped them navigate through dense forest branches. They also had short, high skulls. Their jaws turned downward and they possessed large front teeth.

Scientists have worked for decades to understand these animals. Stephen Czerkas and Yuan Chongxi created the family name in 2002. They first described *Scansoriopteryx heilmanni*. For a long time, it was hard to place them in the dinosaur family tree. In 2008, the discovery of *Epidexipteryx hui* helped define the group more clearly. The 2015 discovery of an adult *Yi qi* was a major breakthrough. It provided the first evidence of adult gliding adaptations in this group.

Their tails were not all the same. This shows how different species adapted to their environments. *Epidexipteryx* had a short tail. It was only about 70% of the length of its torso. This tail held long, ribbon-like feathers for display. In contrast, *Scansoriopteryx* had a very long tail. It was over three times as long as its torso. This tail had a small spray of feathers at the very tip.

All known scansoriopterygids had feathers covering their bodies.

Yi qi restoration
Yi qi restoration

These feathers were often quite simple. *Epidexipteryx* had long feathers on its tail with a central shaft called a rachis. *Yi qi* had "paintbrush-like" feathers. These had long quill-like bases with thin filaments on top. They also had a semilunate carpal. This is a half-moon shaped wrist bone. It allowed them to fold their hands in a bird-like motion.

Most fossils come from the Tiaojishan Formation in China. This area includes the provinces of Liaoning and Hebei.

Size comparison of scansoriopterygid dinosaurs
Size comparison of scansoriopterygid dinosaurs

These fossils date to the mid-to-late Jurassic Period. The formation was likely between 165 and 153 million years old. During this time, the area was a humid, temperate forest. It was filled with ginkgo trees and conifers. The ground was covered in ferns, cycads, and horsetails.

These dinosaurs lived in a very busy ecosystem. They shared the forest with many other creatures. They lived alongside early mammals like *Castorocauda*. They also lived near gliding mammals and pterosaurs. Insects like beetles and mayflies were everywhere.

Yi qi restoration
Yi qi restoration

By studying these fossils, scientists can see how different animals shared the same forest. Scansoriopterygids help us piece together the complex history of life on Earth.

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File:Size comparison of scansoriopterygid dinosaurs.png
Size comparison of scansoriopterygid dinosaurs.png
File:Yi qi restoration.jpg
Yi qi restoration.jpg
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