Department of Earth and Environmental Science, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
PLoS One. 2013 Aug 9;8(8):e69265. doi: 10.1371/journal.pone.0069265. eCollection 2013.
Psittacosaurus is one of the most abundant and speciose genera in the Dinosauria, with fifteen named species. The genus is geographically and temporally widespread with large sample sizes of several of the nominal species allowing detailed analysis of intra- and interspecific variation. We present a reanalysis of three separate, coeval species within the Psittacosauridae; P. lujiatunensis, P. major, and Hongshanosaurus houi from the Lujiatun beds of the Yixian Formation, northeastern China, using three-dimensional geometric morphometrics on a sample set of thirty skulls in combination with a reevaluation of the proposed character states for each species. Using these complementary methods, we show that individual and taphonomic variation are the joint causes of a large range of variation among the skulls when they are plotted in a morphospace. Our results demonstrate that there is only one species of Psittacosaurus within the Lujiatun beds and that the three nominal species represent different taphomorphotypes of P. lujiatunensis. The wide range of geometric morphometric variation in a single species of Psittacosaurus implies that the range of variation found in other dinosaurian groups may also be related to taphonomic distortion rather than interspecific variation. As the morphospace is driven primarily by variation resulting from taphonomic distortion, this study demonstrates that the geometric morphometric approach can only be used with great caution to delineate interspecific variation in Psittacosaurus and likely other dinosaur groups without a complementary evaluation of character states. This study presents the first application of 3D geometric morphometrics to the dinosaurian morphospace and the first attempt to quantify taphonomic variation in dinosaur skulls.
鹦鹉嘴龙是恐龙中最丰富和最多样化的属之一，有十五个命名种。该属在地理和时间上分布广泛，其中几个命名种的样本量很大，允许对种内和种间变异进行详细分析。我们对产自中国东北义县组陆家屯层的三个同时代的鹦鹉嘴龙科的独立种，即鹦鹉嘴龙、大鹦鹉嘴龙和红山嘴龙，进行了重新分析，使用了三维几何形态测量学方法，对 30 个头骨的样本进行了分析，同时重新评估了每个物种的提议特征状态。使用这些互补的方法，我们表明，个体和埋藏学变异是导致头骨在形态空间中出现大范围变异的共同原因。我们的结果表明，陆家屯层只有一个鹦鹉嘴龙种，而三个命名种代表了不同的鹦鹉嘴龙种的埋藏型。单一的鹦鹉嘴龙种存在广泛的几何形态测量变异，这表明在其他恐龙类群中发现的变异范围也可能与埋藏学变形有关，而不是种间变异。由于形态空间主要由埋藏学变形引起的变异驱动，因此本研究表明，只有在对特征状态进行补充评估的情况下，几何形态测量方法才能谨慎地用于界定鹦鹉嘴龙和可能的其他恐龙类群的种间变异。本研究首次将三维几何形态测量学应用于恐龙形态空间，并首次尝试量化恐龙头骨的埋藏学变异。
