Nebreda Sergio M, Hernández Fernández Manuel, Marugán-Lobón Jesús
Centre for the Integration in Palaeobiology, Universidad Autónoma de Madrid, Madrid, 28049, Spain.
The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, California 90037, USA.
Biol Lett. 2025 May;21(5):20240685. doi: 10.1098/rsbl.2024.0685. Epub 2025 May 7.
The origin of flight in avian dinosaurs has been historically an ideal framework for proposing the evolutionary relationship between form and function in limb proportions under the hypothesis of specialized locomotor modules. However, other hypotheses suggest that the evolution of the forelimb and the hindlimb is strongly influenced by shared developmental constraints, entailing that limbs evolve in an integrated manner and keeping the scientific debate open. To assess this, we used an alternative morphometric approach to compare and statistically analyse limb morphological covariation in a phylogenetically broad context across non-avian maniraptoran theropods and modern birds. Our results show that the maniraptoran lineage shares a strong covariation between limb proportions, a pattern indicating that consistent morphological integration has constrained the forelimb and hindlimb evolutionary transformation. Different evolutionary grades within Maniraptora, both volant and non-volant lineages, display distinct and weaker covariation patterns, suggesting the emergence of independent evolutionary trends within such underlying patterns of integration. These findings are consistent with a developmental hypothesis in which the evolutionary transformation of limbs in maniraptoran dinosaurs was influenced by its serial homology, underscored by shared developmental programmes. Thus, limb evolution was not solely driven by modular (functional) specialization for flight.
在专门的运动模块假说下，鸟类恐龙飞行的起源在历史上一直是提出肢体比例中形态与功能进化关系的理想框架。然而，其他假说表明，前肢和后肢的进化受到共同发育限制的强烈影响，这意味着肢体以一种综合的方式进化，使得科学争论仍未定论。为了评估这一点，我们采用了一种替代的形态测量方法，在一个系统发育广泛的背景下，比较并统计分析非鸟类手盗龙类兽脚亚目恐龙和现代鸟类的肢体形态协变。我们的结果表明，手盗龙类谱系在肢体比例之间存在强烈的协变，这种模式表明一致的形态整合限制了前肢和后肢的进化转变。手盗龙类内部不同的进化等级，包括会飞和不会飞的谱系，都表现出不同且较弱的协变模式，这表明在这种潜在的整合模式中出现了独立的进化趋势。这些发现与一个发育假说一致，即在共享发育程序的强调下，手盗龙类恐龙肢体的进化转变受到其系列同源性的影响。因此，肢体进化并非仅仅由飞行的模块化（功能性）特化驱动。
