Megatypus schucherti -

A Web page by Roy J.Beckemeyer  (send mail to royb at southwind.net)

Last Updated: 4 April 2005

Please do not use any of the images of fossil insects or other information from these pages without permission.  This is an ongoing research effort that the author intends to publish in the scientific literature and is presented here as work in progress.  All information © 2002 by Roy J. Beckemeyer.

The image on the right shows two odonate hind wings - that of the Permian Protodonata Megatypus schucherti together with one from a male of the extant Anax junius.  The fossil is from the Elmo, Kansas Permian site.  The Anax junius is also from Kansas, but is about 265 million years more recent.  The images were obtained by scanning the wings on a flat-bed scanner.  Much work has been done by Robin Wootton and others (see the bibliography) to relate the structural geometry and structural characteristics of insect wings to their aerodynamic performance.  Wootton has shown that the relatively stiff and relatively deformable areas of the wings are that way because of the way the wing needs to change shape during the insect's flapping cycle.  Since insects have no muscles within the wings proper to effect any shape changes, these "aeroelastic" characteristics are entirely passive, and result from the layout, shape, and vertical relief of the wing veins, and the nature of the joints between these veins.  Since many fossil odonatoid wings have significant corrugation or fluting preserved, I have undertaken a research program to document the three-dimensional geometry of some of these wings and to try to infer something about the flight characteristics of the Permian forbearers of today's dragonflies.  

ACKNOWLEDGEMENTS: Initial work is with the Megatypus schucherti hind wing, primarily because it is a well-preserved example, and because it was locally available.  Access to it was provided by Ralph Charlton and Sonny Ramaswamy of the Kansas State University Entomology Department.  Other Elmo fossil material is being made available to me by loan from the Yale Peabody Museum courtesy of Tim White, through my research associate relationship with the Johnston Geology Museum at Emporia State University, Michael Morales, Director.  

METHODOLOGY:  1.  Fossil Wings:

The wing is first scanned (above right) on a flat-bed scanner at various resolutions, from 300 to 1200 pixels per inch.  This provides scaled images which can be used for accurate location and measurement of features.  The wings are also photographed (right) more conventionally, as scanning does not necessarily provide the shading that shows the vertical relief that helps in interpretation of the venation.  

The scanned images are then reviewed using Adobe Photoshop, and annotated versions of the images are made.  Veins are identified, and then are digitized by locating vein intersections and entering their x and y coordinates (usually in pixel units) into an Excel Spreadsheet.  Another software program, Sigma Scan Pro 5, is also used, as points located using it are automatically stored in a spreadsheet.  The latter program is also used with in image analysis, wherein it is possible to measure the wing area and to locate the centers of area automatically.

These operations yield the two-dimensional planform geometry and vein locations for the wing.  Here is an example of the type of information that can then be generated:

The wing leading and trailing edges, the major longitudinal veins, and the quarter-chord (the approximate location of the center of lift of the wing) are located in spanwise and chordwise coordinates in centimeter units.  Vein nomenclature follows Riek and Kukalova -Peck (1984).  

Another set of Excel Worksheets are used with these data to compute the moments of area and virtual mass that Ellington (see Bibliography) proposed as ways of characterizing wing geometry.  

Next, the vertical relief of the wing  is measured to provide the three-dimensional geometry.  Several methods can be used, including making latex molds of the fossil, casting plaster impressions, sectioning these casts, and scanning and measuring the cross sections.  The method used here involves a digital depth gage (Fowler Depthmatic, accurate to 0.001 mm) and a measuring fixture (right and left below).  

This yields information such as that shown below, where wing "sections" indicate the corrugation or fluting of the wing.  Note that the vertical relief is exaggerated by the choice of vertical and horizontal scales.

The three-dimensional data can also eventually be used to generate finite-element analysis models of the wing.  

METHODOLGY: 2. Extant Odonata Wings:

Wings of extant Odonata are also scanned and digitized for locating planform coordinates of major longitudinal veins and other features.  

The wings are then cast in clear resin, and the resulting casts are sectioned to provide information on vertical relief of vein corrugations and cross-sectional shape and area of wing veins.  Sections are cut with a jeweler's saw, then polished using a carborundum stone.  

Below left are views of a typical cross section of the wing resulting from a scan of the section, and (below right) a close up of the costal and subcostal veins and wing membrane made by photographing the view through a binocular microscope equipped with a calibrated reticle with a Nikon 990 digital canera.  The section is the second section line from the wing base.  The close-up view shows the most basal of the two triangular-shaped reinforcing cross veins that occur in the Anax junius wing.  These veins are the first and sixth cross veins between the costa (vein at the leading edge of the wing) and subcosta (the longitudinal vein immediately posterior to the costa), and are visible in the wing planform scan (left above).

Here is the cross section of a male Anax junius hind wing a somewhat more outboard spanwise position:

On the right is a close up of the cross sections of the costal, subcostal and anterior radial veins:

The image processing software package Sigma Scan Pro can be used to determine the cross sectional area and center of area of each of these veins.  We begin by assuming the veins to be solid, although they are actually hollow, and they will eventually be represented as tubes.  On the left below is an image of the costal vein with the center of area marked and on the right is a summary of all three of the major anterior veins.  This type of data can be used to compute bending and torsional stiffness characteristics of the wing section.

CLICK HERE TO LINK TO A RECENT PAPER ON THE SUBJECT