Do different disparity proxies converge on a common signal? Insights from the cranial morphometrics and evolutionary history of Pterosauria (Diapsida: Archosauria)
Do different disparity proxies converge on a common signal? Insights from the cranial morphometrics and evolutionary history of Pterosauria (Diapsida: Archosauria)
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DOI：
10.1111/j.1420-9101.2012.02479.x
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发表时间：
2012-05-01
影响因子：
2.1
通讯作者：
Butler, R. J.
中科院分区：
文献类型：
--
作者：
Foth, C.;Brusatte, S. L.;Butler, R. J.
差异，或形态多样性，通常由进化生物学家在地质时间尺度上研究分支的宏观演化史来量化。视差通常使用诸如测量、离散解剖特征或几何形态计量学之类的形态指标来量化。如果不同的指标产生不同的结果，那么在很深的时间内准确量化差异可能是有问题的。然而，尽管如此，很少有研究试图使用多个形态指标来检验单个分支的差异。这里，作为这个问题的一个案例，我们考察了中生代爬行动物分支翼龙的差异，翼龙是一个被广泛研究的类群，在其1.45亿年的演化史上实现了大量的形态、生态和分类多样性。我们首次使用基于地标的几何形态计量学描述了翼龙颅骨形态差异的大尺度模式，并与基于替代度量的翼龙差异计算进行了比较。基于地标的差异计算表明，与基础的非单孔翼龙相比，单窗翼龙在颅骨上的多样性更大(至少在排除异常的厌食性恐龙的情况下是如此)，并且颅骨差异的峰值可能出现在早白垩世，在翼龙进化的相对较晚的时期。值得注意的是，我们的头骨差异结果与基于整个骨骼离散特征和肢体比例数据集的结果大体一致，表明这些不同的方法记录了翼龙形态进化的一致模式。因此，翼龙提供了一个示范案例，表明不同的形态形态代用品可以汇聚在相同的视差信号上，这是令人鼓舞的，因为通常只有一个这样的代用品可以用于以化石为代表的灭绝支系。此外，将系统发育图映射到颅骨形态空间表明翼龙的颅骨形态与系统发育关系密切相关，并可能受到系统发育关系的制约。
Disparity, or morphological diversity, is often quantified by evolutionary biologists investigating the macroevolutionary history of clades over geological timescales. Disparity is typically quantified using proxies for morphology, such as measurements, discrete anatomical characters, or geometric morphometrics. If different proxies produce differing results, then the accurate quantification of disparity in deep time may be problematic. However, despite this, few studies have attempted to examine disparity of a single clade using multiple morphological proxies. Here, as a case study for this question, we examine the disparity of the volant Mesozoic fossil reptile clade Pterosauria, an intensively studied group that achieved substantial morphological, ecological and taxonomic diversity during their 145+ million-year evolutionary history. We characterize broadscale patterns of cranial morphological disparity for pterosaurs for the first time using landmark-based geometric morphometrics and make comparisons to calculations of pterosaur disparity based on alternative metrics. Landmark-based disparity calculations suggest that monofenestratan pterosaurs were more diverse cranially than basal non-monofenestratan pterosaurs (at least when the aberrant anurognathids are excluded), and that peak cranial disparity may have occurred in the Early Cretaceous, relatively late in pterosaur evolution. Significantly, our cranial disparity results are broadly congruent with those based on whole skeleton discrete character and limb proportion data sets, indicating that these divergent approaches document a consistent pattern of pterosaur morphological evolution. Therefore, pterosaurs provide an exemplar case demonstrating that different proxies for morphological form can converge on the same disparity signal, which is encouraging because often only one such proxy is available for extinct clades represented by fossils. Furthermore, mapping phylogeny into cranial morphospace demonstrates that pterosaur cranial morphology is significantly correlated with, and potentially constrained by, phylogenetic relationships.