Prieto-Márquez Albert, Garcia-Porta Joan, Joshi Shantanu H, Norell Mark A, Makovicky Peter J
Institut Català de Paleontologia Miquel Crusafont Universitat Autònoma de Barcelona Barcelona Spain.
Integrative Research Center Field Museum of Natural History Chicago IL USA.
Ecol Evol. 2020 May 22;10(13):6288-6309. doi: 10.1002/ece3.6361. eCollection 2020 Jul.
The fossil record provides compelling examples of heterochrony at macroevolutionary scales such as the peramorphic giant antlers of the Irish elk. Heterochrony has also been invoked in the evolution of the distinctive cranial frill of ceratopsian dinosaurs such as . Although ceratopsian frills vary in size, shape, and ornamentation, quantitative analyses that would allow for testing hypotheses of heterochrony are lacking. Here, we use geometric morphometrics to examine frill shape variation across ceratopsian diversity and within four species preserving growth series. We then test whether the frill constitutes an evolvable module both across and within species, and compare growth trajectories of taxa with ontogenetic growth series to identify heterochronic processes. Evolution of the ceratopsian frill consisted primarily of progressive expansion of its caudal and caudolateral margins, with morphospace occupation following taxonomic groups. Although taphonomic distortion represents a complicating factor, our data support modularity both across and within species. Peramorphosis played an important role in frill evolution, with acceleration operating early in neoceratopsian evolution followed by progenesis in later diverging cornosaurian ceratopsians. Peramorphic evolution of the ceratopsian frill may have been facilitated by the decoupling of this structure from the jaw musculature, an inference that predicts an expansion of morphospace occupation and higher evolutionary rates among ceratopsids as indeed borne out by our data. However, denser sampling of the meager record of early-diverging taxa is required to test this further.
化石记录提供了宏观进化尺度上异时性的令人信服的例子，比如爱尔兰麋鹿的体型增大的巨型鹿角。异时性也被用于解释角龙类恐龙独特的颅饰的进化，例如 。尽管角龙类的颅饰在大小、形状和装饰上有所不同，但缺乏能够检验异时性假说的定量分析。在这里，我们使用几何形态测量学来研究角龙类多样性中以及四个保存有生长序列的物种内部的颅饰形状变化。然后，我们测试颅饰在物种间和物种内是否构成一个可进化的模块，并将具有个体发育生长序列的分类单元的生长轨迹进行比较，以识别异时过程。角龙类颅饰的进化主要包括其尾缘和尾外侧边缘的逐渐扩展，形态空间的占据遵循分类群。尽管埋藏学变形是一个复杂因素，但我们的数据支持物种间和物种内的模块性。体型增大在颅饰进化中起了重要作用，在新角龙类进化早期是加速发育，随后在较晚分化的角龙类角龙中是幼态持续。角龙类颅饰的体型增大进化可能是由于该结构与颌部肌肉组织的解耦而促进的，这一推断预测角龙科动物的形态空间占据会扩大且进化速率更高，我们的数据确实证实了这一点。然而，需要对早期分化分类单元的稀少记录进行更密集的采样来进一步检验这一点。
