Smyth Robert S H, Breithaupt Brent H, Butler Richard J, Falkingham Peter L, Unwin David M
Centre for Palaeobiology & Biosphere Evolution, School of Geography, Geology, and the Environment, University of Leicester, Bennett Building, University Rd, Leicester LE1 7RH, UK.
BLM Wyoming State Office, 5353 Yellowstone Road, Cheyenne, WY 82009, USA.
Curr Biol. 2024 Nov 4;34(21):4894-4907.e3. doi: 10.1016/j.cub.2024.09.014. Epub 2024 Oct 4.
Pterosaurs, the first true flying vertebrates, played a crucial role in Mesozoic terrestrial ecosystems. However, our understanding of their ability to move around on the ground and, more broadly, their terrestrial paleoecology remains limited. Here, we demonstrate an unexpectedly high degree of variation in the hands and feet of pterosaurs, comparable with that observed in extant birds. This suggests that pterosaurs were adapted to a remarkably broad range of non-aerial locomotor ecologies. Small, early, long-tailed pterosaurs (non-pterodactyliforms) exhibit extreme modifications in their hand and foot proportions indicative of climbing lifestyles. By contrast, the hands and feet of later, short-tailed pterosaurs (pterodactyliforms) typically exhibit morphologies consistent with more ground-based locomotor ecologies. These changes in proportions correlate with other modifications to pterosaur anatomy, critically, the separation along the midline of the flight membrane (cruropatagium) that linked the hindlimbs, enabling a much more effective locomotory ability on the ground. Together, these changes map a significant event in tetrapod evolution: a mid-Mesozoic colonization of terrestrial environments by short-tailed pterosaurs. This transition to predominantly ground-based locomotor ecologies did not occur as a single event coinciding with the origin of short-tailed forms but evolved independently within each of the four principal radiations: euctenochasmatians, ornithocheiroids, dsungaripteroids, and azhdarchoids. Invasion of terrestrial environments by pterosaurs facilitated the evolution of a wide range of novel feeding ecologies, while the freedom from limitations imposed by climbing permitted an increase in body size, ultimately enabling the evolution of gigantism in multiple lineages.
翼龙是最早真正会飞的脊椎动物，在中生代陆地生态系统中发挥了关键作用。然而，我们对它们在地面上移动的能力，以及更广泛地说，它们的陆地古生态学的了解仍然有限。在这里，我们展示了翼龙的手部和足部存在出乎意料的高度变异，这与现存鸟类中观察到的变异程度相当。这表明翼龙适应了范围广泛得惊人的非空中运动生态。小型、早期、长尾翼龙（非翼手龙形类）在其手部和足部比例上表现出极端的变化，表明它们具有攀爬的生活方式。相比之下，后期的短尾翼龙（翼手龙形类）的手部和足部通常呈现出与更多基于地面的运动生态相一致的形态。这些比例的变化与翼龙解剖结构的其他改变相关，至关重要的是，连接后肢的飞行膜（胫蹼）沿中线的分离，使得在地面上具有更有效的运动能力。这些变化共同描绘了四足动物进化中的一个重大事件：中生代中期短尾翼龙对陆地环境的殖民。向主要基于地面的运动生态的这种转变并非作为与短尾形态起源同时发生的单一事件出现，而是在四个主要类群：真双型齿翼龙类、鸟掌翼龙类、准噶尔翼龙类和阿氏翼龙类中的每一类中独立进化的。翼龙对陆地环境的入侵促进了广泛的新型觅食生态的进化，同时摆脱了攀爬所带来的限制使得体型得以增大，最终促成了多个谱系中巨型化的进化。
