September 18, 2013
Wind Tunnel Helps Explore Origins Of Dinosaur Flight
[ Watch The Video: Wind Tunnel Helps Understand Bird Flight ]
Michael Harper for redOrbit.com - Your Universe Online
Recent research has uncovered the evolutionary origin of birds, as the limbs of certain dinosaurs transformed into wings and gave these creatures the ability to fly. Scientists at the University of Southampton have taken this research one step farther and now say they understand how feathered dinosaurs developed the ability to use these wings for flight.
For years researchers have studied fossils and debated about the different mechanisms needed to lift a dinosaur into the air and keep it there as it migrated from place to place or hunted for food. Using a wind tunnel, the Southampton scientists found that the location and shape of the Microraptor’s legs and wings were largely irrelevant.
Using anatomically correct models of the dinosaurs, they say the key to this flight is a gliding mechanism which created enough lift to keep them aloft. The resulting paper titled “Aerodynamic performance of the feathered dinosaur Microraptor and the evolution of feathered flight” is published in the current edition of the journal Nature Communications.
The early Cretaceous five-winged paravian Microraptor is known to have been covered in feathers on its arms, legs and tail. The beast's four-winged layout is said to have been an important evolutionary stage in terms of gliding, flapping and, ultimately, flying. These five points of lift — four covered by the wings and a fifth covered by the tail — had been a matter of much debate, as many scientists believed the size of the legs and position of the wings could not have worked together to lift the Microraptor into the air.
After analyzing the model in a wind chamber, however, the Southampton scientists say these debates are irrelevant. The combination of high lift and aerodynamics was largely at play here, factors which the Microraptor had working in its favor.
“Significant to the evolution of flight, we show that Microraptor did not require a sophisticated, ‘modern’ wing morphology to undertake effective glides, as the high-lift coefficient regime is less dependent upon detail of wing morphology,” said coauthor Dr. Gareth Dyke. Senior Lecturer in Vertebrate Paleontology at the University of Southampton.
“This is consistent with the fossil record, and also with the hypothesis that symmetric ‘flight’ feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form aerodynamically capable surfaces.”
With efficiency and lift working in concert, the Southampton scientists now say the Microraptor was able to glide across the sky at relatively low altitudes without losing much height. This meant they could theoretically stay in the air longer and move from tree to tree with minimal effort.
Researchers from McGill University also recently uncovered the evolutionary pathways necessary to transform ordinary limbs into wings. Looking to fossil data from Maniraptors, professor Hans Larsson and team found that these limbs began evolving dramatically and in spite of the relative size of the body. The back limbs, or the legs, began to shrink quickly while the forearms began to grow longer. These forearms became the earliest wings and acted as airfoils. The smaller, shrunken hind legs allowed the dinosaurs to guide and control their flight and perch on small branches upon landing.
“Our findings suggest that the limb lengths of birds had to be dissociated from general body size before they could radiate so successfully,” explained Alexander Dececchi, one of the study’s researchers.
“It may be that this fact is what allowed them to become more than just another lineage of maniraptorans and led them to expand to the wide range of limb shapes and sizes present in today’s birds.”