Further consideration of placoderm evolution

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Abstract
The flight performances of Pteranodon ingens and Nyctosaurus gracilis from the Upper Cretaceous of Kansas were modeled using data from a Sailvane hang-glider which has an airfoil similar to that of a pterosaur. The aerodynamics of large pterosaurs were mainly dictated by three parameters: low wing loadings, wings with high aspect ratios, and the performance of the thin cambered airfoil. Given maximum muscular efforts, Nyctosaurus and Pteranodon could have taken off at airspeeds of 1.5 and 4 m/sec, respectively. These airspeeds included windspeed, running speed, and a flapping component, so takeoff presented no problems. Landing speeds were also slow. The sustained power output of Pteranodon was not enough for continuous level flapping flight. A maximum burst of power allowed level flapping or climbing flight. However, this required anaerobic muscle operation and was only maintained briefly. The power profile shows that Pteranodon was a soarer. On the other hand, the sustained power output of Nyctosaurus was more than enough for continuous level flapping. However, the animal probably reduced the metabolic cost of transport by alternate gliding and flapping as in gulls. Inasmuch as the power required for soaring is much lower than that for flapping or alternate gliding and flapping, Nyctosaurus probably soared whenever the weather was suitable. The gliding performance of the Kansas pterosaurs was characterized by slow horizontal and vertical speeds, excellent gliding angles, and narrow ranges of horizontal speeds. The pterosaurs flew far from shore in a warm, calm climate. Their aerodynamics were ideal for slope soaring along a low relief coastline and for convection-current soaring. Pteranodon and probably also Nyctosaurus obtained seafood by skimming the waves and/or landing and seizing fish and crustaceans. Compared to soaring birds, large pterosaurs were specialized for low power requirements and a narrow range of slow horizontal flight speeds.