South American Canids are endemic and form a monophyletic clade supported by molecular and morphological data, with the exception of Urocyon cinereoargenteus, which is a typical North American form. South American canids occur in almost all environments in continent, and exhibit diet diversity and large size variation. Here we analyzed the skull ontogeny by applying 3D geometric morphometric techniques, in a well-represented sample of South American canids, with the aim of exploring variation in cranial size and shape as well as evolutionary patterns of such variation. The sample consisted of 1227 crania of the 11 living species of South American canids and 92 crania of Canis lupus and Vulpes vulpes, which were considered as out-groups. South American canids exhibited similar shape and diet (they are mostly omnivorous), which implies similar mechanical commitments, which are reflected in their almost uniform skulls. However, it is possible that cranial similarity is related to a shared evolutionary history with a short time of divergence. Speothos venaticus differed in its ontogenetic trajectory, with the difference being stronger between adults of this species and the remaining canids. The skull configuration is consistent with the hyper-carnivorous diet. In the case of Chrysocyon brachyurus, size plays an important role in the structure of a skull, giving rise to remarkable morphological differences from other species, although in terminal stages of its ontogeny.

南美犬科动物是地方性疾病，形成由分子和形态学数据支持的单系进化枝，除了典型的北美形式的灰狐猴（Urocyon cinereoargenteus）。南美犬科动物几乎出现在该大陆的所有环境中，并且饮食结构多样且大小各异。在这里，我们通过使用3D几何形态计量学技术，在一个代表性良好的南美犬科动物样本中分析了头骨的个体发育，目的是探索颅骨大小和形状的变异以及这种变异的进化模式。样本包括1227头骨南美犬科动物的生活11种和92头骨的狼和赤狐，它们被视为外群体。南美犬科动物表现出相似的形状和饮食（大多是杂食性的），这意味着相似的机械动作，反映在它们几乎统一的头骨上。但是，颅骨相似性可能与具有短分歧时间的共同进化史有关。斜方天蛾的个体发育轨迹有所不同，该物种的成虫与其余犬齿之间的差异更强。头骨的形状与肉食性饮食相一致。就短尾金龟而言，大小在头骨的结构中起着重要作用，尽管在其个体发育的末期，但与其他物种的形态差异却很明显。