carried out the experiments and completed the 3D reconstruction and video of the Caudipteryx robot; J.-S.Z. Ji, Q., Currie, P. J., Norell, M. A. Thus the structure of the vane is more open than generally realized. Most of the robot was built from ABS plastic, but the wing plumage was composed of trimmed feathers taken from modern birds (Fig. It helps birds regulate their body temperature and wards off the loss of body heat. Although the results of our preliminary analysis of the downstroke suggest that the amounts of lift and thrust produced during flapping would have been minimal, the potential aerodynamic utility of flapping in Caudipteryx nevertheless requires further investigation. 6d,e; Supplementary Videos3 and 4); and lift and thrust/drag produced by the wing, shown as functions of the flapping angle (Fig. 3c,d. 1) is the best known; several specimens of the two species C. dongi and C. zoui having been described from the Lower Cretaceous Yixian Formation of northeast China10,11,12. A realistic 3D wing geometry was assumed in this part of the analysis, and Caudipteryx was considered to be running horizontally in still air at a speed of 8m/s. The mass flow is given by m=Bv, indicating that mass flow is a function of the density of air (air, in kg/m3), the area of the wing projected into a vertical plane (B, in m2), and velocity (v, in m/s, representing the common magnitude of v1 and v2). The wings are assumed to be held in a horizontal position, and Caudipteryx is assumed to be running on level ground. McMasters, J. H. & Cummings, R. M Airplane Design and the Biomechanics of Flight-A More Completely Multi-disciplinaryPerspective. & OConnor, J. K. Complexities and novelties in the early evolution of avian flight, as seen in the Mesozoic Yanliao and Jehol Biotas of northeast China. https://doi.org/10.1007/s00114-008-0488-3, https://doi.org/10.1371/journal.pone.0153446, CAD model of skeleton of Caudipteryx robot, http://creativecommons.org/licenses/by/4.0/. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies10,11,12. The results of this procedure offer some preliminary insights into the likely aerodynamic effects of flapping while running, even though flapping was not explicitly modelled in our study. EBFFs in Beipiaosaurus. PubMedGoogle Scholar. and J.-S.Z. Arrows point to EBFFs. We initially used equations and assumptions from classical aerodynamics to estimate the lift and drag forces produced by the wings of Caudipteryx while running, representing the wing and its position in an essentially abstract manner. 4a). Of the three genera, Caudipteryx (Fig. Pennaceous feathers have a central shaft (or rachis) with vanes spreading to either side. The discovery raises the intriguing prospect that flight may have developed multiple times in the ancestors of birds. Biol. Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. Aerodynamic forces are averaged over the whole wing for a flapping angle of =5 and considered to be acting at the wings center of mass (b). Integument, Parts I and II 197233 (U.S. Government Printing Office, 1972), Gatesy, S. M. & Dial, K. P. From frond to fan: Archaeopteryx and the evolution of short-tailed birds. Thank you for visiting nature.com. c, Pelvis under normal light. See Supplementary Information for details. It is notable that CD(profile) will decrease as velocity increases, and therefore Reynolds number increases, too. where CL and CD represent coefficients of lift and drag, respectively, SP is the area of the wing projected into a plane perpendicular to the airflow (approximately half the true wing area, at an optimal angle of attack) and v represents airflow velocity. Vertebrata PalAsiatica 38, 111127 (2000). 2a,b), which may be expressed as, where p is pressure, is the density of the air, and v is the velocity of the air relative to the wing, which in still air corresponds to the velocity of the running animal. Representation of the wing as a series of cross-sections for each of the six flapping angles considered (c), showing the twist along the length of the wing assumed for each flapping angle. 4, 719723 (2008), OConnor, J. K., Chiappe, L. M., Chuong, C., Bottjer, D. J. There is need for a model of feather evolution that gives attention to the function and adaptive advantage of intermediate structures. Nature 464, 13381341 (2010). c, Right forelimb. CL and CD are the lift and drag coefficients of the Caudipteryx wing, while represents the density of the moving air and s is the effective area of the wing. and JavaScript. 33, 91124 (2002), Ji, Q., Norell, M. A., Gao, K., Ji, S. & Ren, D. The distribution of integumentary structures in a feathered dinosaur. Feathered dinosaurs is a term used to describe dinosaurs, particularly maniraptoran dromaeosaurs, that were covered in plumage; either filament-like Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. & Guo, Y. S5. This type of feather is present in most modern birds, and has been shown in some species of maniraptoran dinosaurs. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Jing-Shan Zhao. Introduction to the Aerodynamics of Flight. Scale bar, 5cm. Aerodynamic forces (a) arising from interaction of incident air with rectangular wing. At the lower wind speed of 3.5m/s, the two wings produced a total of 0.32N of lift and 0.15N of drag, whereas at the higher wind speed of 6.0m/s they produced 0.55N of lift and 0.29N of drag (Table1). PubMed Central 86, 91102 (2012), Xu, X., Zheng, X. 05 July 2021, Communications Biology In the first phase of our theoretical analysis of the wings of a running Caudipteryx, we used classical aerodynamic equations to estimate the forces the wings would have produced when extended laterally in a fixed position during running at constant speed on level ground in still air. Four-winged dinosaurs from China. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Internet Explorer). ( A) Beipiaosaurus sp. Based on the expression given above for mass flow, the approximate vertical and horizontal aerodynamic forces on a hypothetical rectangular Caudipteryx wing are: where b=wl sin (m2), l=0.100m and w=0.240m. In addition to this mathematical analysis, the fluid dynamics software package ABAQUS was used to simulate airflow patterns about the hypothetical flat rectangular wing, assuming the wing was held at various angles of attack during steady running at 8m/s (Fig. Robot based on skeletal proportions of Caudipteryx (a), with anatomically realistic wings. Science 335, 12151219 (2012), Longrich, N. R. Structure and function of hindlimb feathers in Archaeopteryx lithographica. Naturwissenschaften 92, 173177 (2005), OConnor, J. et al. Fowler, D. W., Freedman, E. A., Scannella, J. Vertebrata PalAsiatica 47, 311329 (2009), Li, Q. et al. Pennaceous feathers have a rachis with vanes or vaxillum spreading to either side. Only the two-dimensional shape of each wing, as opposed to its cross-sectional area, affected these calculations. Flight feathers (remiges and rectrices) are specialized types of pennaceous feathers, adapted for high loadings and often strongly asymmetric for improved flight performance[WP]. The input metabolic power needed for the muscles to generate Phorizontal would be Pinput=Phorizontal/, where represents the efficiency of the muscles of Caudipteryx. However, the aerodynamic forces on each wing would have been small, not exceeding 0.05N in magnitude. Flight characteristics of birds: I. PubMed The amount of deflection is maximal at =20, with the leading edge of the wing rising by 1.8cm (Fig. 5d). German paleontologists led by Dr Oliver Rauhut of the Ludwig-Maximilians-Universitt in Munich, Germany, have discovered a new specimen of Archaeopteryx a feathered reptile that lived during the Jurassic period, about 150 million years ago with extensive feather preservation. Google Scholar. Alerstam, T. et al. Nature 410, 10841088 (2001), Xu, X. This pressure imposed by the airflow causes variable amounts of stress and deflection across the wing surface. Staatliche Naturwissenschaftliche Sammlungen Bayerns, Bayerische Staatssammlung fr Palontologie und Geologie, Richard-Wagner-Strae 10, 80333 Munich, Germany. Nature 464, 13381341 (2010), Nachtigall, W. & Kempf, B. Vergleichende Untersuchungen zur flugbiologischen Funktion des Daumenfittichs (Alula spuria) bei Vgeln. Each downstroke position was defined by an angle of elevation or depression relative to the horizontal, which we term here the flapping angle , and by twisting of the wing surface along its length, causing variation in the angle of attack across different parts of the wing. Article Palontol. CAS Altshuler, D. L. et al. Important features of Caudipteryx evidence from two nearly complete new specimens. McGraw-Hill, (1991). Foth, C., Tischlinger, H. & Rauhut, O. W. M. New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers. b, Presacral vertebral column. [1] In Fig. If material is not included in the articles Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. The Mesozoic radiation of birds. Vertebrata PalAsiatica 47, 178189 (2008). & You, H. Homology and potential cellular and molecular mechanisms for the development of unique feather morphologies in early birds. Because it is unlikely that Caudipteryx had a range of shoulder joint motion approaching that of modern birds, we considered only six modest flapping angles (=10, 5, 0, 5, 10 and 20, with negative values corresponding to elevation and positive ones to depression) in this part of our analysis. The authors declare no competing financial interests. Correspondence to A study that really holds water | MIT Technology Review Similarly, the wings of the Caudipteryx robot constructed for this study produced a total lift of only 0.55N and a total drag of only 0.29N even at an incident windspeed of 6m/s. You are using a browser version with limited support for CSS. Google Scholar, Godefroit, P. et al. the lift coefficient associated with an optimal angle of attack) of a slotted wing19. Winged forelimbs of the small theropod dinosaur, $${p}+\frac{1}{2}\rho {{v}}^{2}={\rm{Constant}}$$, $$\{\begin{array}{c}{{F}}_{{L}}=\frac{1}{2}\rho {{S}}_{{p}}{{C}}_{{L}}{{v}}^{2}\\ {{F}}_{{D}}=\frac{1}{2}{\rho }{{S}}_{{p}}{{C}}_{{D}}{{v}}^{2}\end{array}$$, $$\{\begin{array}{c}{{C}}_{{D}({profile})}\approx \frac{{{S}}_{{w}}}{{{S}}_{{p}}}\frac{1.33}{{\mathrm{Re}}^{0.5}}\approx \frac{2.6}{{\mathrm{Re}}^{0.5}}\\ {{C}}_{{D}({induced})}\approx \frac{{k}{{C}}_{{L}}^{2}}{\pi {A}}\end{array}$$, $${C}_{D}\approx {C}_{D({profile})}+{C}_{D({induced})}\approx \frac{2.6}{{\mathrm{Re}}^{0.5}}+\frac{k{C}_{{L}}^{2}}{\pi A}$$, $$\{\begin{array}{c}{{F}}_{{D}({profile})}=\frac{1}{2}\rho {{S}}_{{p}}{{C}}_{{D}({profile})}{{v}}^{2}\Rightarrow {{F}}_{{D}({profile})}=\frac{1.33\rho {{S}}_{{p}}{{v}}^{2}}{{\mathrm{Re}}^{0.5}}\\ {{F}}_{{D}({induced})}=\frac{1}{2}\rho {{S}}_{{p}}{{C}}_{{D}({induced})}{{v}}^{2}\Rightarrow {{F}}_{{D}({induced})}=\frac{\rho {k}{{C}}_{{L}}^{2}{{S}}_{{p}}{{v}}^{2}}{2\pi {A}}\end{array}$$, $${{F}}_{{D}}={{F}}_{{D}({profile})}+{{F}}_{{D}({induced})}=\frac{1}{2}\rho {{S}}_{{p}}(\frac{2.6}{{\mathrm{Re}}^{0.5}}+\frac{{k}{{C}}_{{L}}^{2}}{\pi {A}}){{v}}^{2}$$, $${{F}}_{D{,}\text{total}}=2[{{F}}_{{D}({profile})}+{{F}}_{{D}({induced})}]+{{F}}_{D{,}{body}}=\frac{1}{2}{\rho }{{v}}^{2}[2{{S}}_{{p}}(\frac{2.6}{{\mathrm{Re}}^{0.5}}+\frac{{k}{{C}}_{{L}}^{2}}{\pi {A}})+{{S}}_{{b}}{{C}}_{{D},{body}}]$$, $${{\boldsymbol{F}}}_{{w}}=\mathop{{m}}\limits^{\bullet }({{v}}_{2}-{{v}}_{1})$$, \(\mathop{{m}}\limits^{\bullet }=\frac{{dm}}{{dt}}\), $$\{\begin{array}{ccc}\sum {{F}}_{x} & = & 0\to {{F}}_{w(x)}+\mathop{{m}}\limits^{\bullet }({{v}}_{2(x)}-{{v}}_{1(x)})\\ & = & 0\to {{F}}_{w(x)}\\ & = & \mathop{{m}}\limits^{\bullet }({{v}}_{1(x)}-{{v}}_{2(x)})\to {{F}}_{w(x)}\\ & = & \mathop{{mv}}\limits^{\bullet }(1-{\rm{c}}{\rm{o}}{\rm{s}}\alpha )\\ \sum {{F}}_{y} & = & 0\Rightarrow {{F}}_{w(y)}+\mathop{{m}}\limits^{\bullet }({{v}}_{2(y)}-{{v}}_{1(y)})\\ & = & 0\to {{F}}_{w(y)}\\ & = & \mathop{{m}}\limits^{\bullet }({{v}}_{1(y)}-{{v}}_{2(y)})\to {{F}}_{w(y)}\\ & = & \mathop{{mv}}\limits^{\bullet }[0-(-{\rm{s}}{\rm{i}}{\rm{n}}\alpha )]\end{array}$$, $$\{\begin{array}{c}{{F}}_{{w}({x})}=\rho {b}{{v}}^{2}(1-{\rm{c}}{\rm{o}}{\rm{s}}\alpha )\\ {{F}}_{{w}({y})}=\rho {b}{{v}}^{2}{\rm{s}}{\rm{i}}{\rm{n}}\alpha \end{array}$$, $${v}=\sqrt{{({{v}}_{{x}}+{{v}}_{2}{\rm{c}}{\rm{o}}{\rm{s}}\theta )}^{2}+{({{v}}_{2}{\rm{s}}{\rm{i}}{\rm{n}}\theta -{{v}}_{{y}})}^{2}}$$, $$\psi ={\rm{a}}{\rm{r}}{\rm{c}}{\rm{t}}{\rm{a}}{\rm{n}}(\frac{{{v}}_{2}{\rm{s}}{\rm{i}}{\rm{n}}\theta -{{v}}_{{y}}}{{{v}}_{2}{\rm{c}}{\rm{o}}{\rm{s}}\theta +{{v}}_{{x}}})$$, $$\alpha =\phi +\psi =\phi +\arctan (\frac{{{v}}_{2}\,\sin \,\theta -{{v}}_{y}}{{{v}}_{2}\,\cos \,\theta +{{v}}_{x}})$$, $$\{\begin{array}{c}{{F}}_{{L}}=\frac{1}{2}{{C}}_{{L}}\rho {s}{{v}}^{2}=\frac{1}{2}{{C}}_{{L}}\rho {s}[{({{v}}_{{x}}+{{v}}_{2}{\rm{c}}{\rm{o}}{\rm{s}}\theta )}^{2}+{({{v}}_{2}{\rm{s}}{\rm{i}}{\rm{n}}\theta -{{v}}_{{y}})}^{2}]\\ {{F}}_{{D}}=\frac{1}{2}{{C}}_{{D}}\rho {s}{{v}}^{2}=\frac{1}{2}{{C}}_{{D}}\rho {s}[{({{v}}_{{x}}+{{v}}_{2}{\rm{c}}{\rm{o}}{\rm{s}}\theta )}^{2}+{({{v}}_{2}{\rm{s}}{\rm{i}}{\rm{n}}\theta -{{v}}_{{y}})}^{2}]\end{array}$$, $$\begin{array}{c}{\boldsymbol{R}}=[\begin{array}{c}{{R}}_{{x}}({{v}}_{{x}}{,}{{v}}_{{y}}{,}{{v}}_{2})\\ {{R}}_{{y}}({{v}}_{{x}}{,}{{v}}_{{y}}{,}{{v}}_{2})\end{array}]=[\begin{array}{c}{{F}}_{{D}}\,{\rm{c}}{\rm{o}}{\rm{s}}\,\psi -{{F}}_{{L}}\,{\rm{s}}{\rm{i}}{\rm{n}}\,\psi \\ {{F}}_{{D}}\,{\rm{s}}{\rm{i}}{\rm{n}}\,\psi +{{F}}_{{L}}\,{\rm{c}}{\rm{o}}{\rm{s}}\,\psi \end{array}]\\ {\boldsymbol{R}}=[\begin{array}{c}\frac{1}{2}\rho {s}[{({{v}}_{{x}}+{{v}}_{2}{\rm{c}}{\rm{o}}{\rm{s}}\theta )}^{2}+{({{v}}_{2}{\rm{s}}{\rm{i}}{\rm{n}}\theta -{{v}}_{{y}})}^{2}]({{C}}_{{D}}\,{\rm{c}}{\rm{o}}{\rm{s}}\,\psi -{{C}}_{{L}}\,{\rm{s}}{\rm{i}}{\rm{n}}\,\psi )\\ \frac{1}{2}\rho {s}[{({{v}}_{{x}}+{v}_{2}{\rm{c}}{\rm{o}}{\rm{s}}\theta )}^{2}+{({{v}}_{2}{\rm{s}}{\rm{i}}{\rm{n}}\theta -{{v}}_{{y}})}^{2}]({{C}}_{{D}}\,{\rm{s}}{\rm{i}}{\rm{n}}\,\psi +{{C}}_{{L}}\,{\rm{c}}{\rm{o}}{\rm{s}}\,\psi )\end{array}]\end{array}$$, $${{P}}_{{horizontal}}={{\boldsymbol{F}}}_{{D},{total}}\cdot {\boldsymbol{v}}=\frac{1}{2}\rho {{v}}^{3}[2{{S}}_{{p}}(\frac{2.6}{{\mathrm{Re}}^{0.5}}+\frac{{k}{{C}}_{L}^{2}}{\pi {A}})+{{A}}_{{e}}]$$, https://doi.org/10.1038/s41598-018-35966-4. Mayr then argues that signaling feathers are localized, whereas in modern birds pennaceous feathers cover the entire body. Bundle, M. W. & Dial, K. P. Mechanics of wing-assisted incline running (WAIR). Furthermore, we did not explicitly model flapping behaviour in our study. & Brush, A. H. The evolutionary origin and diversification of feathers. Pennaceous feathers are also known as contour feathers. S3 shows Rx and Ry as functions of incident airflow angle (), with the wings fully unfolded (wing length 240mm; aspect ratio ~3.2, calculated as the square of wing length divided by wing area). Physics Education 38(6), 497503 (2003). Google Scholar. Volume 27 Springer-Verlag, (1990). Article In the meantime, to ensure continued support, we are displaying the site without styles In order to produce aerodynamic thrust that might contribute to propulsion, a running Caudipteryx would need to flap its wings, not merely hold them extended in a fixed position relative to the body. a, Preserved cranial remains under ultraviolet light. The biophysics of bird flight: functional relationships integrate aerodynamics, morphology, kinematics, muscles, and sensors. Dimensions of rectangle representing each wing (a), based on outline of left wing seen in dorsal view, and aerodynamic forces (b) arising from interaction of incident air with rectangular wing. A new specimen of the Early Cretaceous bird Hongshanornis longicresta: insights into the aerodynamics and diet of a basal ornithuromorph. J. Zool. Flight speeds among bird species: Allometric and phylogenetic effects. a, Rhachides of the primaries shown as yellow dashed lines. Yellow dots represent feathers of the 11th specimen of Archaeopteryx; black dots represent data of modern birds; red rectangles represent data of Confuciusornithidae. The stalk above the calamus is a solid rachis having an umbilical groove on its underside. Historical Biology 16, 8592 (2004). The authors declare no competing interests. Arrow points to the basal end of a Int. While the mathematical fixed-wing analyses varied somewhat in their results, all showed the total lift and drag experienced by the animal (or their near-equivalents) increasing as a function of running speed, but nevertheless having values under 4N even at a running speed of 8m/s, the estimated maximum for Caudipteryx. When averaged over the entire wing (Fig. AIAA 42nd Aerospace Sciences Meeting, Reno NV, AIAA Paper 2004-0532, Vol 6 (2004). By submitting a comment you agree to abide by our Terms and Community Guidelines. Nature 498, 359362 (2013), Prum, R. O. 4a). This analysis indicates that lift and drag would both have been considerably greater at higher running speeds, while higher aspect ratios (i.e. Lift and drag curves in this figure were calculated for a range of running velocities, always assuming a headwind with an airspeed of 0.5m/s and a lift coefficient of 2.038,39,40,41,42. Scale bar, 1cm. A newly discovered specimen from the Solnhofen limestone in Bavaria only the eleventh since 1861 shows a generous covering of feathers all over the body.
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