School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
Department of Earth Sciences, University College London, London, WC1E 6BT, UK.
Sci Rep. 2022 Apr 21;12(1):6540. doi: 10.1038/s41598-022-10507-2.
Pterosaurs thrived in and around water for 160 + million years but their take-off from water is poorly understood. A purportedly low floating position and forward centre of gravity barred pterosaurs from a bird-like bipedal running launch. Quadrupedal water launch similar to extant water-feeding birds and bats has been proposed for the largest pterosaurs, such as Anhanguera and Quetzalcoatlus. However, quadrupedal water launch has never been demonstrated in smaller pterosaurs, including those living around the Tethys Sea in the Late Jurassic Solnhofen Lagoon. Using Laser-Stimulated Fluorescence, we singled out aurorazhdarchid specimen MB.R.3531 that alone preserved specific soft tissues among more than a dozen well-preserved Solnhofen pterosaur specimens. These soft tissues pertain to primary propulsive contact surfaces needed for quadrupedal water launch (pedal webbing and soft tissues from an articulated forelimb) that permit robust calculations of its dynamic feasibility without the need to make assumptions about contact areas. A first-principles-based dynamics model of MB.R.3531 reveals that quadrupedal water launch was theoretically feasible and that webbed feet significantly impacted launch performance. Three key factors limiting water launch performance in all pterosaurs are identified, providing a foundation for understanding water launch evolution: available propulsive contact area, forelimb extension range and forelimb extension power about the shoulder.
翼龙在水中和周围生活了 1600 多万年，但它们如何从水中起飞仍未被充分理解。据称，翼龙的低位浮起姿势和靠前的重心使其无法像鸟类那样进行两足奔跑式起飞。为了让最大的翼龙，如 Anhanguera 和 Quetzalcoatlus，能够起飞，有人提出了类似于现生水鸟和蝙蝠的四足水起飞方式。然而，这种四足水起飞方式从未在较小的翼龙身上得到证明，包括生活在侏罗纪晚期索伦霍芬泻湖的那些翼龙。我们使用激光刺激荧光技术，专门挑选出了 MB.R.3531 这具标本，它是在十几个保存完好的索伦霍芬翼龙标本中唯一保存了特定软组织的标本。这些软组织与四足水起飞所需的主要推进接触表面有关（蹼状的足和连接的前肢的软组织），这使得我们能够在无需对接触面积做出假设的情况下，对其动态可行性进行强有力的计算。基于第一性原理的 MB.R.3531 动力学模型表明，四足水起飞在理论上是可行的，并且蹼状的脚对起飞性能有显著影响。确定了限制所有翼龙水起飞性能的三个关键因素，为理解水起飞进化提供了基础：可用的推进接触面积、前肢伸展范围和肩部的前肢伸展力量。
