Info graphic about bird flight. Watercolor, Pen, Photoshop
“Trends in theropod–avian evolution. The evolution of flight in theropod dinosaurs was marked by many changes in skeletal morphology, feather morphology, body size, and mass distribution. Clades indicated by capitalized letters, and feathered theropods by bold italics (all feathered theropods up through the basal pygostylians included). Clade and theropod names, character state changes and sources listed in S2; though details of phylogenetic relationships are unclear in some places (e.g. many basal taxa, Alvarezsaurids, Rahonavis, Archaeopteryx ), general trends appear to hold. Whole body images from ; reprinted with permission of The Johns Hopkins University Press. Individual bone elements adapted from [81–84]; all individual bone elements correspond to the featured theropod. Pennaceous and non-pennaceous feathers indicated by black and gray shading, respectively; (S): symmetric feathers, (A): asymmetric feathers, (?): feather structure probably pennaceous but poorly preserved or not well documented. Body size estimates based on adult theropods (see S2 for details), though smaller feathered juveniles have been described (e.g. Epidendrosaurus).”
Heers, A.M. and K.P. Dial. (2012) From extant to extinct: locomotor ontogeny and the evolution of avian flight. Trends in Ecology and Evolution. (pdf)
When: Late Miocene (~6 million years ago)
What: Argentavis is the largest flighted bird there ever was. Its wingspan has been estimated at 23 feet (~7 meters), almost double that of the largest flying bird that soars today’s skys, the wandering albatross (Diomedea exulans). All specimens of this avaian have been found in Argentina, hence its name, which means ‘magnificent Argentine bird’. Recent studies looking at the biomechanics of flight in Argentavis have determined that it was a soaring bird, like today’s condors and vultures. It would have easily glided upon the strong thermals above the Argentine pampas, but getting up to those winds was a bit more of a challenge. It was too large to just flap its wings and take off, even when it was standing in a strong headwind. Instead Argentavis would have had to run down a steep hill or jumped from a high perch in order to take to the skies. Once it was up there, however, it is estimated it could have soared for hours, hunting for prey as it rode the late afternoon thermals.
Meganeura - The Giant Dragonfly
When: Carboniferous (~305-299 million years ago)
What: Meganeura is the largest dragonfly, with a wingspan of 2.5 feet (~75 cm) in some specimens. The largest living dragonfly is a comparatively weensy 7.5 inches (~19 cm) across at the wings. A scientific debate had centred upon why Meganeura was able to become so large. It has been suggested that it was only able to reach such a great size due to the relatively higher levels of oxygen in the Carboniferous air. This is based partly upon the way most modern insects respire, they do not truly breathe, but instead simply diffusion oxygen throughout their small bodies. However, more recent studies show that larger insects do breathe via compression and expansion of their trachea. Additionally insects much larger than those today have been found in later rocks which do not show evidence of elevated oxygen levels. More research needs to be done to determine the impact of oxygen levels upon the maximum size of insects.
Only a few fossils have been found of Meganeura, but despite this, almost every scene ever of a Carboniferous forest has one of these animals perched upon a giant club moss tree. I do not blame them, I could not resist either. Other animals in these dense forests with Meganeura were a gaggle of other gigantic insects and arthropods, a great variety of amphibians, and the first reptiles. This was the start of the true colonization of land by vertebrates; it has also been suggested it was the arrival of these predators which limited the size of insects such as Meganeura in later time periods.
When: Eocene (all known fossils from a deposit 52.5 million years old)
Where: Wyoming, USA
What: Onychonycteris is the most basal bat currently known. It differs from living bats in having claws on all five fingers, whereas living bats have lost them. This form also has relatively shorter arms and fingers, as well as longer legs and tail than any other bat, fossil or extant. Onychonycteris was an extremely important find, as allowed us to answer a long standing question about bat evolution: Which came first, flight or echolocation? This taxon was capable of flight, and detailed examination of the cranium revealed that it could not echolocate. Thus, bats took to the skies before they developed a system for seeing with their ears.
This amazing fossil is from the Green River fossil lagerstatten in southwestern Wyoming, and is one of two known complete specimens. This example is not the holotype (the specimen which bears the name) as while it looks absolutely gorgeous, the second specimen was arranged on the rock slab in such a way more of the skull could be studied. Additionally, this specimen was actually in the hands of a private collector, and thus not fully available to science. That is until the specimen was mailed, unannounced, to Dr. Nancy Simmons at the American Museum of Natural History, New York. She was working on publishing this taxon at the time, and the private collector had been informed of this, so the family sent the specimen to allow her the best examination possible. That was one awesome package to open, believe me!
Nemicolopterus - perhaps the smallest of the pterasaurs
When: Early Cretaceous (~120 million years ago)
What: Nemicolopterus is a pterosaur. It is the smallest one known, its wing span was just 10 inches (25 centimeters) from tip to tip. It was well adapted for roosting in trees with its highly curved toes and sharp claws and is thought to have eaten insects. Nemicolopterus was one of the few pterosaurs to live far inland, most of the group were fish eaters living near or on coasts. The validity of Nemicolopterus is debated; there are strong arguments in favor of it actually being a juvenile Sinopterus. The single specimen of this proposed minute pterosaur has a very large skull for its size and has a simular level of bone fusion as other known hatchling pterosaurs - it is thought the young could fly at a very young age. Sinopterus has a wingspan of 4 feet (~1.2 meters), which is on the small end for pterosaurs.
Pterosaurs are archosaurs, members of the group that also includes crocodiles and dinosaurs. Within Archosauria they are more closely related to dinosaurs than to crocodiles. This clade is the first vertebrate lineage to have evolved powered flight, already flying by the late Triassic (~220 million years ago). The pterosaur wing was primarily supported by a hyper-elongated 4th digit, leaving digits I-III free in most taxa. This makes pterosaurs the only flying vertebrate group to have retained free digits, as both birds and bats lost the full use of their fingers in the evolution of their wing mechanisms. Pterosaurs went extinct at the end of the Cretaceous period (~65 million years ago).