Paleo Profiles: Yi qi

A reconstruction of the Yi qi. From Emily Willoughby, emilywilloughby.com, (May 2015)

Today on Paleo Profiles we will be looking at a very unique dinosaur from Jurassic China: the Yi qi (Strange Wing). This bat like dinosaur is a recent discovery and shows us how diverse dinosaurs were. So let's look at China's bat-like 'Strange Wing'.

Discovery and Fossils

Currently, we only have own partial specimen of Yi and it was only formally described in 2015. It was initially discovered by a farmer called Wang Jianrong in Qinglong County back in 2007; he recognised it as a possible dinosaur fossil so he sold it to the Shandong Tianyu Museum of Nature. As often with fossil discoveries, it remained in storage until someone could formally describe the fossil in 2015. A group of ten palaeontologists evaluated the fossil including Xu Xing - Xu is one of China's most prominent palaeontologists describing, or co-describing, many major discoveries including the bird-like Microraptor and the fossil which showed tyrannosaurs were feathered, Yutyrannus. In 2015 their findings were published in Nature and the little dinosaur was named Yi. Although partial, major sections of the Yi has been preserved including the majority of the pigeon-sized body, parts of the skull, and imprints from a membrane which made up the animal's wings.

Biology

Examples of the Yi qi soft tissue

Yi was in a family known as Scansoriopterygids - a family which was closely related to the ancestors to modern birds. Three genera, including Yi, made up the Scansoriopterygids which are all biologically similar and lived alongside one another. The largest, and best known before 2015, was the Epidexipteryx due to it being the best preserved. However, for years it had been reconstructed incorrectly. Yi was the first Scansoriopterygid to be discovered with preserved membranes which connected the long fingers together, and palaeontologists, and paleo-artists, at times have a general fault of 'skin-wrapping' fossils. This means that non-mammalian fossils are regularly reconstructed with the skin tracing the skeletons - features like muscles, filaments, or extra skin are often overlooked. As a result Epidexipteryx was reconstructed without membranes leading to palaeontologists believing that it lived similar to a species of lemur called the aye-aye. The BBC documentary Planet Dinosaur reconstructed Epidexipteryx in this way as well:

The discovery of the Yi showed that Scansoriopterygids were not like aye-ayes, but really bats or more likely flying squirrels. This had been suggested before the discovery of Yi - most notably by Andrea Cau. Although we have the membrane of the Yi it is not fully preserved so there are several different reconstructions of the wing - the discoverers stated that 'the flight apparatus of Yi cannot be confidently reconstructed...However, the range of possible flight apparatus configurations can be explored by considering different reconstructions'. When first discovered the media reported it as being a 'dinosaur bat' but the paper itself disagreed with that interpretation - Yi just vaguely resembled one. They argued that based on realistic membrane placement it would be a glider. Yi and other Scansoriopterygids had long tail feathers which have traditionally been seen as being for display. Likely that it still true, possibly brightly coloured it could be used to assert dominance or attract a mate, like with the feathers of a male peafowl. With the Scansoriopterygids they were also possibly used to help the dinosaurs glide - like the tail on a flying squirrel it could act as a rudder to steer. It did not have the exact body for relying solely on gliding so it could possibly rely on short bursts of powered flight.

One of the key discoveries associated with Yi and other Scansoriopterygids are the presence of feathers covering the body. They were closely related to the ancestors of modern birds, just instead being an evolutionary dead end, so it would be natural for them to be covered in feathers - albeit these were simple feathers, not something you would expect to see on a fully grown modern bird. Nevertheless, by use of an electron microscope it is possible to know, vaguely, what colour the feathers were. Preserved pigments leads us to believe that Yi had black feathers except on the head which was a yellow-brown hue. Yi and its cousins were perfectly adapted to life in the trees with flattened bodies and long fingers which allowed it to grip hold of tree trunks. The diet of Yi is still unknown but reasonable guesses can be made. Teeth and the presence of pterosaurs in the area with similar teeth would suggest that Scansoriopterygids were primarily insectivores, although their diet could include berries.

When and Where
Yi and other Scansoriopterygids lived during the Jurassic period, in particular the Callovian or Oxfordian, around 160 million years ago. During this time the world was warmer, wetter, and richer in oxygen. Where Yi came from was no exception. The Tiaojishan Formation in Northeast China has been believed to be either a sub-tropical or temperate climate, as well as being both warm and humid based on fossilised tree rings. As a result, the Yi would never experience the cold. Based on its arboreal lifestyle, and limited ability to undertake powered flight, this would mean that the Yi would be limited to forests. The region was very volcanic. Tiaojishan Formation has many layers showing occasional ash fall from volcanic eruptions - something that many Chinese fossil sights experienced. This is why Chinese dinosaurs are so well preserved that they regularly show evidence of feathers. Ash buries and preserves those unfortunate enough to be caught in the cloud - just think of how well-preserved the unfortunate victims of Pompeii are. Consequently, Chinese fossil sites every year gives us more and more well-preserved dinosaur remains - Yi is far from the only dinosaur that we know what colour they were due to their pigments being preserved.

Neighbours

A Jeholopterus, a pterosaur which lived alongside Yi

Yi had a wide variety of animal life living alongside it. Among these included the other two Scansoriopterygids genera, Scansoriopteryx and Epidexipteryx, but both were a lot smaller than the Yi. In fact, three of the smallest dinosaurs lived at the same time in the same place - Scansoriopteryx, Epidexipteryx, and Aurornis. Other arboreal dinosaurs resembled modern birds - such as Anchiornis - and likely competed with Yi. Pterosaurs were common in the region with around fifteen species being known to live alongside Yi. The Scansoriopterygids were not the only gliding animals - the flying squirrel like Volaticotherium could be found in the Tiaojishan forests. What about terrestrial dinosaurs? There are a few including a heterodontosaurid called Tianyulong and a few dinosaurs, including Anchiornis, lived alongside them. From other Chinese fossil sights around the same time we do know larger dinosaurs were roaming Jurassic China - such as Sinraptor, actually a relative of Allosaurus and not raptors. There is a possibility that a large carnivore related to Sinraptor stalked the land.

Thank you for reading. The sources I have used are as follows:
-Xing Xu, Xiaoting Zheng, Corwin Sullivan, Xiaoli Wang, Lida Xing, Yan Wang, Xiaomei Zhang, Jingmai K. O’Connor, Fucheng Zhang, & Yanhong Pan, 'A Bizarre Maniraptoran theropod with preserved evidence of membranous wings', Nature, 521:7550, (2015), 70-73
-'Yi', prehistoric-wildlife.com, [Accessed 20/03/2019]
-'Epidexipteryx', prehistoric-wildlife.com, [Accessed 20/03/2019]
-Gregory S. Paul, The Princeton Field Guide to Dinosaurs, Second Edition, (Princeton: Princeton University Press, 2016)
-Trey the Explainer, 'Paleo Profile - Yi qi', Youtube, (29/04/2015), [Accessed 20/03/2019]
-Wang Yongdong, Saiki Ken'ichi, Zhang Wu, and Zheng Shaeolin, 'Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning, China', Progress in Natural Science, 16:9, (2006), 222-230