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yi: carnivore dinosaur from the Jurassic era

Yi Facts

Pronunciation: EE

Name meaning: Wing

Diet	Carnivore
Wing Span	0.06m
Length	0.15m
Weight	15 g
Environment	Air
Era	Jurassic
Period	Middle Jurassic
Type	Theropod
Location	China

Yi was a remarkable tiny theropod dinosaur that lived approximately 165 million years ago during the Middle Jurassic period in what is now China. This extraordinary creature represents one of the most unusual dinosaurs ever discovered, measuring just 15 centimetres in total length and weighing only about 15 grams—roughly the size of a sparrow.

What made Yi truly exceptional was its unique wing structure. Unlike the feathered wings of modern birds or other feathered dinosaurs, Yi possessed bat-like membranous wings stretched between elongated finger bones. This membrane wing design, combined with long ribbon-like tail feathers, created a flying apparatus unlike anything else known in the dinosaur world. The creature's body was covered in simple filamentous feathers, giving it a fuzzy appearance.

As a carnivorous theropod, Yi likely fed on insects and other small prey that it could catch whilst gliding between trees in the forests of ancient China. Its sharp claws and teeth were well-suited for grasping and processing small invertebrates. The creature's lifestyle was probably similar to modern flying squirrels, using its wings to glide from tree to tree rather than achieving powered flight like birds.

Yi's discovery revolutionised our understanding of early flight evolution, showing that dinosaurs experimented with multiple solutions to achieving aerial locomotion. This tiny gliding theropod represents a fascinating evolutionary experiment that ultimately proved unsuccessful, as no other dinosaurs are known to have developed similar membrane wings.

What made Yi distinctive?

Yi's most distinctive feature was its bat-like membranous wings stretched between greatly elongated finger bones, making it unique among all known dinosaurs. It also possessed long ribbon-like tail feathers and a body covered in simple fuzzy feathers, combined with its extraordinarily small size of just 15 centimetres long.

Behaviour

Yi was likely an arboreal glider that moved between trees in forest canopies, using its membrane wings to glide rather than achieve true powered flight. It probably spent much of its time climbing and clambering through branches using its sharp claws, hunting for insects and small invertebrates amongst the foliage.

Fun Facts About Yi

Yi has the shortest scientific name of any dinosaur, consisting of just two letters
Yi is the only known dinosaur to have developed bat-like membrane wings rather than feathered wings
The single known Yi specimen is so well-preserved that scientists could identify traces of the wing membrane under UV light
Yi's wing design represents a completely different solution to flight from that taken by birds, showing evolution's creativity
Despite having wings, Yi was probably incapable of true powered flight and could only glide between trees

Discovery

Yi was first described by Xu Xing and colleagues in 2015. The original fossils were discovered at Tiaojishan Formation, Hebei Province, China.

Yi FAQ

What did Yi eat?

Yi was a carnivore that fed primarily on insects and other small invertebrates. Its tiny size and sharp teeth were perfectly adapted for catching and eating small prey like beetles, flies, and other bugs that it encountered whilst gliding and climbing through the forest canopy.

How big was Yi?

Yi was extraordinarily small, measuring just 6 centimetres tall at the hip and 15 centimetres in total length. It weighed only about 15 grams, making it roughly the same size as a modern sparrow and one of the smallest dinosaurs ever discovered.

When did Yi live?

Yi lived during the Middle Jurassic period, approximately 165.3 million years ago. This was a time when forests covered much of what is now China, providing the perfect arboreal environment for this tiny gliding dinosaur.

Where was Yi found?

Yi was discovered in China, specifically in the Tiaojishan Formation in Hebei Province. This fossil site has produced many exceptionally well-preserved feathered dinosaurs and early birds from the Middle Jurassic period.

How do you pronounce Yi?

Yi is pronounced simply as 'EE', like the letter E. It's remarkably straightforward and is the shortest dinosaur name ever given, consisting of just two letters in total.

What does Yi mean?

Yi means 'wing' in Mandarin Chinese. This name was chosen to reflect the creature's most remarkable feature—its unique bat-like membrane wings that made it unlike any other known dinosaur.

How fast could Yi run?

Yi's running speed is unknown, but given its tiny size and specialised gliding lifestyle, it likely wasn't built for fast ground movement. Instead, it was adapted for climbing and gliding between trees rather than running.

What type of dinosaur was Yi?

Yi was a theropod dinosaur, specifically a member of the family Scansoriopterygidae. Despite being a theropod like T. rex, Yi was utterly different—tiny, fuzzy, and equipped with membrane wings for gliding through ancient forests.

Was Yi related to birds?

Yes, as a theropod dinosaur, Yi was part of the same major group that gave rise to birds. However, Yi's membrane wings represent a completely different evolutionary approach to flight from the feathered wings that led to modern birds.

How many Yi fossils have been found?

Only one Yi specimen has been discovered so far. This single fossil is remarkably well-preserved, with traces of the wing membranes still visible under ultraviolet light, providing scientists with detailed information about this unique dinosaur's anatomy.