The origin of phenotypic diversity among higher clades is one of the most fundamental topics in evolutionary biology. However, due to methodological challenges, few studies have assessed rates of evolution and phenotypic disparity across broad scales of time to understand the evolutionary dynamics behind the origin and early evolution of new clades. Here, we provide a total-evidence dating approach to this problem in diapsid reptiles. We find major chronological gaps between periods of high evolutionary rates (phenotypic and molecular) and expansion in phenotypic disparity in reptile evolution. Importantly, many instances of accelerated phenotypic evolution are detected at the origin of major clades and body plans, but not concurrent with previously proposed periods of adaptive radiation. Furthermore, strongly heterogenic rates of evolution mark the acquisition of similarly adapted functional types, and the origin of snakes is marked by the highest rates of phenotypic evolution in diapsid history.

高等进化枝中表型多样性的起源是进化生物学中最基本的主题之一。然而，由于方法论的挑战，很少有研究评估广泛时间范围内的进化率和表型差异，以了解新进化枝的起源和早期进化背后的进化动态。在这里，我们为双孔类爬行动物中的这个问题提供了一种全证据测年方法。我们发现爬行动物进化中高进化率（表型和分子）时期与表型差异扩大之间存在主要的时间间隔。重要的是，许多加速表型进化的实例是在主要进化枝和身体计划的起源处检测到的，但与先前提出的适应性辐射时期并不同时发生。此外，强烈的异质性进化速率标志着相似适应性功能类型的获得，而蛇的起源则以双孔类历史上最高的表型进化速率为标志。