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Flying Dinosaurs

Flying Dinosaurs
Did you know that birds are actually thought to have evolved from dinosaurs? This article enlists some ancient fliers and predecessors of modern birds.
Prabhakar Pillai
Last Updated: Feb 19, 2018
Dinosaurs are a clade of reptiles that existed during the Mesozoic Era, i.e., around 65 to 230 million years ago. Their sizes varied from the diminutive Anchiornis, 34 cm long and weighing just 110 grams, to the massive Argentinosaurus, more than 20 m long and weighing more than 60 tons.

Their diet was diverse; much like the modern classification of animals based on diet, some dinosaurs were herbivores, some were carnivores, some were omnivores and some were specialized scavengers. Likewise, some were strictly terrestrial, some were aquatic, and some had developed adaptations that afforded them a rudimentary skill of flight.

Few dinosaurs, if any, could match the ability, modification and innate instinct for flight seen in modern birds, but in these humble beginnings lay the start of the evolutionary causeway that would culminate in the emergence of modern birds - the aves. But before diving into the subject of flying dinosaurs, here's a summary of the clade Dinosauria.

Dinosaurs are primarily classified into 2 categories based on their hip structure:
The word 'Saurischia' comes from the Greek word sauros, which means 'lizard', and ischion, which means 'hip joint'. The saurischian dinosaurs had a hip structure resembling that of modern lizards. Saurischians are further classified into 2 subdivisions.
  • Theropods, being one of them, moved on two feet and were mostly carnivorous. This category of dinosaurs is almost exclusively associated in popular culture with the Tyrannosaurus rex. The venom-spitting 'little one' dinosaur from 'Jurassic Park' is also a theropod - a Dilophosaurus, although it has been depicted smaller than in actuality, and the ability to spit venom is entirely fictitious.
  • Sauropodomorphs, which had long necks, moved on four feet and were mostly herbivorous. These were one of the largest creatures to ever inhabit the Earth. They performed the ecological role equivalent to modern giraffes, their long necks allowing them to feed on the topmost branches of trees. 'Dino', the pet dinosaur of the Flintstones, is a prosauropod, which were, as precursors to the sauropods, smaller than sauropods and could walk on two feet. Also, giant sauropods have been shown on numerous occasions in 'The Flintstones', often as a crane.
The word 'Ornithischia' comes from the Greek word ornithes, which means 'birds', and ischion meaning 'hip joint'. The ornithischian hip structure resembled that of modern birds.

Although ornithischian hip structure resembled modern birds, birds have evolved from a theropod clade known as Maniraptora. Since the clade was an evolutionary bridge between reptiles and birds, many species have been found to have had a mixture of reptilian and avian features.

Air Fossil One

Archaeopteryx is a genus within the group Maniraptora. The word 'Archaeopteryx' comes from the Greek word archaios, meaning ancient, and pteryx, meaning wing. The Archaeopteryx prospered in the Late Jurassic Period, i.e., around 150 million years ago (Ma). It lived mainly on the coasts around what is now Germany - back then, an equatorial archipelago - and most of its fossils have been found in Bavaria.
It could grow to be up to 0.5 m long, roughly the size of a raven. The first Archaeopteryx find was a feather, described in 1861. Since then, 11 fossils have been discovered, shedding light on the appearance and behavior of the Archaeopteryx. The feathers of this ancient dinosaur greatly resembled those of modern birds, though it is disputed whether it used its wings for gliding or 'true' flying. An important difference between the modern birds and the Archaeopteryx is that the Archaeopteryx had teeth, which modern birds lack.

Microraptor belonged to the Dromaeosauridae subfamily of the Deinonychosauria family. The word 'microraptor' comes from the Greek word micro, meaning small, and raptor, meaning one who seizes. It lived in the forests of Asia in the early Cretaceous period. It is one of the many cretaceous fossils discovered in the Jiufotang formation in Liaoning, China.
Microraptor was less than a meter long, usually not exceeding 90 cm, and weighed about 2 lbs. It had a second pair of wings attached to its feet. It is conjectured that the Microraptor was arboreal and used its two sets of wings to glide between trees, much like the 'flying' squirrel, since a terrestrial life would have been difficult thanks to its second pair of wings being attached to its legs.

Rahonavis ostromi:
Rahonavis was discovered in Madagascar in 1995. It lived in the Late Cretaceous period, about 70 Ma.
Rahonavis could either have been a deinonychosaur or an avialan. It is currently classified as a Dromaeosaurid, a subclass of Deinonychosauria, but it could have been a primitive avialan, or a link between the two. There is controversy over the reliability of the discovered remains; the sole Rahonavis find was discovered along with the remains of another unrelated (in evolutionary terms) dinosaur, and not far from an avialan species, which was also established on the basis of that solitary find. Although the bones deemed to constitute the Rahonavis genus were found in proximity to each other, the remains may have been a compound of different species.
Rahonavis has been described to grow up to a length of 70 cm. It could probably fly more gracefully than the earlier Archaeopteryx and Microraptor, but would be bettered by modern birds.

Archaeopteryx, Microraptor and Rahonavis were genera within the clade 'Maniraptora', but not directly related to modern birds. The following divisions fall within the clade 'Avialae' and are thus direct ancestors of modern birds.

The family Confuciusornithidae was named, obviously, in honor of Confucius. It consists of four genera:
  • Changchengornis
    It's represented by the solitary species C. hengdaoziensis. The genus was thus named after the Chinese name of the Great Wall of China, 'changcheng'.
  • Confuciusornis
    It is represented by C. sanctus, C. dui, C. feducciai and C. jianchangensis.
  • Eoconfuciusornis
    It is represented by the solitary species E. zhengi.
  • Jinzhouornis
    It is represented by J. yixianensis and J. zhangjiyingia.
    The existence of this genus is doubted due to the similarities between the claimed Jinzhouornis species and those of the genera Confuciusornis and Changchengornis.
Confuciusornithidae fossils were found in mainland China (PRC), in the Yixian, Jiufotang and Dabeigou formations in Liaoning and Hebei. They grew to about 50-60 cm in length, comparable to a crow. They had feathers similar to those of modern birds, including the presence of both shafted and down feathers. Confuciusornithidans also lacked teeth, although this is an example of convergent evolution and not proof of direct evolutionary link to aves. They had a pronounced pair of ribbon-like tail feathers comparable in appearance (though not in structure) to those of male birds-of-paradise.

The name of the Enantiornithes subgroup comes from the Greek word enantio, which means 'opposite to', and 'ornithes', which means birds. It was thus named because even though its members resembled modern birds in most aspects, they had teeth, wings culminating in claws and a different skeletal structure, differing particularly in the arrangement of the shoulder joint and the tarsometatarsus. They flourished in the Cretaceous period of a wide range of habitat, including the Americas, Eurasia and Australasia.
This subgroup encompasses 3 families, adding up to 16 genera.
Avisauridae includes the genera:
  • Avisaurus
  • Bauxitornis
  • Concornis
  • Cuspirostrisornis
  • Enantiophoenix
  • Halimornis
  • Intiornis
  • Mystiornis
  • Neuquenornis
  • Soroavisaurus
Gobipterygidae includes the genera:
  • Gobipteryx
  • Vescornis
Longipterygidae includes the genera:
  • Boluochia
  • Camptodontus
  • Longipteryx
  • Longirostravis
  • Rapaxavis
  • Shanweiniao
As mentioned above, enantiornithines lived in a large number of habitats, and performed different ecological roles depending upon their respective location. Some examples of the roles played by enantiornithines include that of fish-catchers (ecologically analogous to kingfishers), shorebirds (analogous to sandpipers and plovers) and swimmers (analogous to ducks). Despite a preference to aquatic habitat, enantiornithine fossils have been found inland as well, although a majority of them are fragmented.

The genus Yanornis was discovered in the Jiufotang Formation of Liaoning, China. It was named after the Yan dynasty of ancient China, whose capital, Chaoyang, was the site of the discovery. Only one species, Y. martini has been described so far.
They are one of the closest relatives of modern birds, and were the best flyers in this list. They had many modern adaptations, such as a well-developed wishbone and a shoulder joint much like modern birds, that helped them fly better and more fluently. The presence of a sturdy wishbone also meant that Yanornis could walk as well as fly. They were about the size of a large parrot: 35-40 cm in length. They were omnivorous and had toothed beaks.

Like its close relative Yanornis, the genus Yixianornis was discovered in the Jiufotang Formation in China. Weirdly, its name comes from the other prominent formation in the Liaoning region, Yixian. The sole species discovered has been named Y. grabaui.
In many aspects, it was very similar to Yanornis. The only major difference was the size; Yixianornis was smaller than the Yanornis and was about 20 cm long.
Yixianornis, Yanornis and their close relative Songlingornis form the Yanornithiformes or Songlingornithidae family, which is the closest ancient relative of modern birds.
There is some debate over whether birds evolved from saurischian dinosaurs or ornithischian, but a majority of researchers conclude in favor of a saurischian origin and a development of the 'actual' ornithischia (bird hip), completely unrelated from that of the original ornithischian dinosaurs.

The primary relatives of the modern birds never were masters of the sky, because the evolutionary ladder had not reached the necessary rung yet, and they lived in times dominated by other flying reptiles, namely the pterosaurs (which, although aerial, are not technically 'dinosaurs'). It is the aves, descendants of the flying dinosaurs, that perfected and improved upon the genetically inherited technique and well and truly mastered the skies.