Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2006 Jan 7;273(1582):119-26.
doi: 10.1098/rspb.2005.3278.

High lift function of the pteroid bone and forewing of pterosaurs

Matthew T Wilkinson  1 , David M Unwin, Charles P Ellington
Affiliations

High lift function of the pteroid bone and forewing of pterosaurs

Matthew T Wilkinson et al. Proc Biol Sci. .

Abstract

The pteroid bone is a rod-like element found only in pterosaurs, the flying reptiles of the Mesozoic. It articulated at the wrist, and supported a membranous forewing in front of the inner part of the wing spar. The function of this bone, particularly its orientation, has been much debated. It is widely believed that it pointed towards the body, and that the forewing was relatively narrow. An alternative hypothesis states that it was directed forwards during flight, resulting in a much broader forewing that acted as a leading edge flap. We tested scale models in a wind tunnel to determine the aerodynamic consequences of these conflicting hypotheses, and found that performance is greatly improved if the pteroid is directed forwards: the lift: drag ratios are superior and the maximum lift is exceptionally high in comparison with conventional aerofoils. This high lift capability may have enabled even the largest pterosaurs to take off and land without difficulty.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Skeletal reconstruction of A. santanae. (a) Reconstructed skeleton of the right wing and membrane outlines in dorsal view, adapted from Wellnhofer (1991b), showing the pteroid in the antero-ventral orientation, supporting a broad propatagium (solid line) and in the medial orientation, supporting a narrow propatagium (broken line): scale bar=200 mm. (b) Right medial carpal in distal view and right pteroid in proximal view, showing the articular surfaces of the carpal–pteroid joint: scale bar=20 mm. (c) Right wrist in antero-medial view, showing articular motion of the pteroid. Two planes have been superimposed, intersecting at the carpal–pteroid joint—one parallel to the wing spar, one normal to it. During the initial phase of flexion the pteroid (solid line) occupies the normal plane, and angulation thus takes the form of pure depression. During the second phase the articular head of the pteroid rotates laterally with respect to the medial carpal, and angulation therefore gradually shifts from depression to adduction. The pteroid swings out of the normal plane until at the limit of flexion (broken line) it comes to occupy the parallel plane. Abbreviations: ch, cheiropatagium; cr, cruropatagium; ds, distal syncarpal; f, femur; fov, fovea of the medial carpal; h, humerus; lf, lateral facet of the pteroid; mc, medial carpal; mf, medial facet of the pteroid; pro, propatagium; ps, proximal syncarpal; pt, pteroid; r, radius; t, tibiotarsus; u, ulna; wf, wing-finger; wm, wing-metacarpal.
Figure 2
Figure 2
Cross-sections of the wing of A. santanae. (a) Three-dimensional reconstruction of the fleshed-out wing skeleton, cheiropatagium, cruropatagium, and the narrow and broad reconstructions of the propatagium, indicating the plane of the cross-section used for the wind tunnel models. (b–d) Wing sections, with (b) broad, (c) narrow and (d) no propatagium. All three sections are shown at an angle of attack of 0°. Scale bar=50 mm. Abbreviations and symbols: bp, broad propatagium; np, narrow propatagium; s, spar; θe, entry angle; θpd, propatagium deflection angle.
Figure 3
Figure 3
Wind tunnel results for the pterosaur wing sections. (a) Polar diagram, in which the lift and profile drag forces measured for each model have been converted into their respective dimensionless coefficients, CL and CD,pro (equations (4.1) and (4.2)), and plotted against each other. Each point represents a CL and CD,pro value measured at a single angle of attack, and angle of attack increases from −2° at the bottom left to 20° at the top right. Open circles, broad forewing model; closed circles, narrow forewing model; triangles, model without a forewing. (b) L : D ratios. Symbols as in (a). (c) Polar diagram showing the effects of variation in θpd on the performance of the broad propatagium model. Open squares, θpd=30°; closed squares, θpd=40°; crosses, θpd=50°. The solid line indicates the best performance over the entire angle of attack range, and it is this composite polar for the broad propatagium model that has been plotted in (a). (d–f) Polar diagram showing the effects of variation in ϵ on the performance of (d) the broad propatagium model, (e) the narrow propatagium model and (f) the model without a propatagium. Open diamonds, ϵ=0.02; closed diamonds, ϵ=0.04; open triangles, ϵ=0.06. The solid lines again indicate the best performance, and are plotted in (a).
See this image and copyright information in PMC

References

    1. Alexander R.M. All-time giants: the largest animals and their problems. Palaeontology. 1998;41:1231–1245.
    1. Applin, Z. T., Gentry, G. L. & Takallu, M. A. 1995 Wing pressure distributions from subsonic tests of a high-wing transport model. NASA-TM4583.
    1. Bennett S.C. The ontogeny of Pteranodon and other pterosaurs. Paleobiology. 1993;19:92–106.
    1. Bennett S.C. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Palaeontographica A. 2001;260:1–153.
    1. Bramwell C.D, Whitfield G.R. Biomechanics of Pteranodon. Phil. Trans. R. Soc. B. 1974;267:503–581.

Publication types

LinkOut - more resources