Flight in non-avian dinosaurs

It has become a well accepted fact that birds are a type of flying dinosaur. Less well known is that they were not the only dinosaurs to take to the air.

Anchiornis was an early deinonychosaur that lived in what is now China around 160 million years ago. It had some parachuting ability thanks to the large feathers on its arms and legs. These feathers were not proper airfoils despite the great length of the arms, suggesting a reduction in flight ability from a possible flying ancestor (Paul, 2010). This would mean both that flight in dinosaurs goes back earlier than previously thought and that the first flying dinosaurs may have been non-avian.

Figure 1: An Anchiornis chases a small mammal through a late Jurassic forest. Artist: Emily Willoughby.

The dromaeosaurs were a group of deinonychosaurs containing members who possessed genuine powered flight. A good example of flying were the microraptorines, small omnivorous dromaeosaurs living in China and North America around 130-75 million years ago. While microraptorines have often been claimed to have been mere gliders their skeletal features show them to have been not only capable of flight, but in fact better flyers than the "first bird" Archaeopteryx (Paul, 2010). Their shoulders were placed so high they could easily perform full vertical flight strokes with their long forewings. Unlike birds, they did not use a sternal keel to assist in flight but instead used powerful deltoid muscles (Agnolin & Novas, 2013).

Figure 2: A Microraptor flies to a landing perch. Artist: Justine Lee.

Another flying dromaeosaur was the unenlaginine Rahonavis, who lived in Madagascar around 75-70 million years ago. Other known unenlaginines, as well as other larger dromaeosaurs such as Velociraptor and Deinonychus had lost the ability to fly. As adults that is. It is, however, possible the chicks still possessed some flight ability (Paul, 2010).

Figure 3: Some Rahonavis up in some trees. Artist: Vasika Yasnjith Udurawane.

The oviraptorosaurs were a group of short-tailed cousins to the deinonychosaurs who, while flightless, may have descended from flying ancestors (Paul, 2002 & 2010). Additionally, the therizinosaurs were cousins of the deinonychosaurs and oviraptorosaurs who may have come from gliders, who may in turn have come from flyers. As strange as it seems, even such groups as the ornithomimosaurs and the tyrannosaurs may ultimately have come from flying ancestry (Paul, 2002).

Figure 4: A family of Caudipteryx- a type of early oviraptorosaur. Oviraptorosaurs may have been secondarily flightless dinosaurs descended from flying ancestors.  Artist: Emily Willoughby.

Next post shall discuss the most well known flying dinosaurs- the birds.

References

Agnolin, F. L. & Novas, P. E. (2013). Avian Ancestors A Review of the Phylogenetic Relationships of the Theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae. Springer: Netherlands.

Paul, G. S. (2002). Dinosaurs of the Air. The John Hopkins University Press: Baltimore, Maryland.
Paul, G. S. (2010). Dinosaurs: A Field Guide. A & C Black Publishers Ltd: London.

Image Sources
Figure 1: Accessed April 14, 2015, from http://fc02.deviantart.net/fs71/f/2010/082/1/d/Anchiornis___new_version_by_Ferahgo_the_Assassin.jpg
Figure 2: Accessed April 14, 2015, from https://gwawinapterus.files.wordpress.com/2013/04/picture.png
Figure 3: Accessed April 14, 2015, from http://fc04.deviantart.net/fs71/f/2011/357/1/3/rahonavis_ostromi_by_vasix-d4jyevw.jpg
Figure 4: Accessed April 14, 2015, from  https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjo2FX3KUM9e-FogVGhEjxAkmRLmDJnzRC1lXN_-e_XnjQI1Cofk0Xz_3enBapjiDRe7xOjjVJXQuPf2b3OHc5pAqwbcpKsKMIeWQ3siMIHGjXYtrdz_U1grzUrDF9ahFIxlqgZ9IpVcA/s1600/Caudipteryx.jpg