The ACTUAL flying Microraptor paper in PNAS

["Thomas R. Holtz, Jr." <tholtz@umd.edu>]

Alexander, D.E., E. Gong, L.D. Martin, D.A. Burnham & A.R. Falk. 2010. Model 
tests of gliding with different hindwing configurations in the four-winged 
dromaeosaurid Microraptor gui. PNAS 107:2972-2976; doi:10.1073/pnas.0911852107

Abstract

Fossils of the remarkable dromaeosaurid Microraptor gui and relatives clearly 
show well-developed flight feathers on the hind limbs as well as the front 
limbs. No modern vertebrate has hind limbs functioning as independent, fully 
developed wings; so, lacking a living example, little agreement exists on the 
functional morphology or likely flight configuration of the hindwing. Using a 
detailed reconstruction based on the actual skeleton of one individual, cast in 
the round, we developed light-weight, three-dimensional physical models and 
performed glide tests with anatomically reasonable hindwing configurations. 
Models were tested with hindwings abducted and extended laterally, as well as 
with a previously described biplane configuration. Although the hip joint 
requires the hindwing to have at least 20Â of negative dihedral (anhedral), all 
configurations were quite stable gliders. Glide angles ranged from 3Â to 21Â 
with a mean estimated equilibrium angle of 13.7Â, giving a lift to drag ratio 
of 4.1:1 and a lift coefficient of 0.64. The abducted hindwing modelâs 
equilibrium glide speed corresponds to a glide speed in the living animal of 
10.6 mÂsâ1. Although the biplane model glided almost as well as the other 
models, it was structurally deficient and required an unlikely weight 
distribution (very heavy head) for stable gliding. Our model with laterally 
abducted hindwings represents a biologically and aerodynamically reasonable 
configuration for this four-winged gliding animal. M. guiâs feathered 
hindwings, although effective for gliding, would have seriously hampered 
terrestrial locomotion.

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A functional and not phylogenetic paper, despite the emphasis of the Ruben 
commentary already discussed. Basically the technical paper from the Kansas 
contribution to Nova's The Four-Winged Dinosaur special of a few years ago.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
http://www.geol.umd.edu/~jmerck/eltsite/
Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA