Closely related species are expected to resemble each other because of inheritance of features from their common ancestors, which are therefore said to carry phylogenetic signal. Cowbirds (Molothrus) are icterids well known from being interspecific brood parasites, but their taxonomy and evolutionary relationships have varied considerably based on morphology alone. In turn, these relationships became unsupported by molecular phylogenies, lending lower value to morphological data in general. However, the osteology of cowbirds has not yet been studied under a quantitative phylogenetic framework and it is uncertain whether their skulls carry phylogenetic signal. In order to test this, we assembled a data matrix, including continuous and discrete characters of the skull of cowbirds and allies, and analyzed it with two complementary approaches under the evolutionary framework provided by molecular phylogenies. We first took a multivariate approach, exploring the occupation of a phylomorphospace based on skull data and estimating the amount and significance of phylogenetic signal by calculation of the K_mult statistic. The second approach relied on a Maximum Parsimony optimization of characters on a scaffold tree. Our results indicate that, although some homoplasy exists, the skull of cowbirds and allies carries significant phylogenetic signal and provides useful characters to diagnose Molothrus and other still poorly diagnosed clades. This first comparative approach is promising and opens the possibility of integrating data from fossils, while encouraging further osteological analyses in cowbirds and other icterids.

由于从其共同祖先继承特征，因此密切相关的物种有望彼此相似，因此据说它们携带着系统发生信号。牛bird（Molothrus）是从种间寄生虫中广为人知的黄疸，但仅基于形态学，它们的分类和进化关系就相差很大。反过来，这些关系也不再受到分子系统发育学的支持，因此一般来说形态学数据的价值较低。然而，尚未在定量的系统发育框架下研究牛鸟的骨学，并且不确定其头骨是否携带系统发育信号。为了对此进行测试，我们组装了一个数据矩阵，其中包括牛鸟和盟友头骨的连续和离散特征，并在分子系统发育提供的进化框架下，通过两种互补方法对其进行了分析。我们首先采用多变量方法，K _Mult统计。第二种方法依赖于在支架树上的字符的最大简约优化。我们的结果表明，尽管存在一些同质异体，但牛鸟和盟友的头骨携带着重要的系统发育信号，并为诊断Molothrus和其他诊断仍然不佳的进化枝提供了有用的特征。这种第一种比较方法很有希望，并为整合来自化石的数据提供了可能性，同时鼓励对牛鸟和其他黄疸动物进行进一步的骨学分析。