Mayr Gerald
Senckenberg Research Institute and Natural History Museum Frankfurt, Ornithological Section, Frankfurt am Main, Germany.
J Morphol. 2025 Aug;286(8):e70070. doi: 10.1002/jmor.70070.
The avian quadrate plays a critical role in cranial kinesis, but few comparative studies exist of its morphological variation across higher-level taxa. The present paper surveys the occurrence of a markedly concave articular facet of the condylus medialis. It is detailed that this feature, for which the term trochlea lateralis is introduced, may represent an apomorphy of a higher-level clade that includes the Aequornithes (gaviiforms, procellariiforms, suliforms, pelecaniforms, and allies), Phaethontimorphae (tropicbirds, sunbittern, and kagu), Mirandornithes (flamingos and grebes), and Gruiformes (cranes and allies). Like many other morphological characters, the occurrence of the trochlea lateralis shows homoplasy. However, at least one analysis of sequence data found a clade including the aforementioned four taxa, the interrelationships of which are not conclusively resolved in other studies. A trochlea lateralis is present in birds with different cranial morphologies and feeding adaptations, so that its occurrence often seems to have a phylogenetic (shared common ancestry) rather than a functional origin. The morphology of the condylus medialis of the quadrate may also bear on the affinities of some fossil taxa, such as the early Eocene Halcyornithidae and Messelasturidae, in which a trochlea lateralis is present.
鸟类的方骨在颅骨运动中起着关键作用，但关于其在高级分类群中的形态变异的比较研究却很少。本文调查了内侧髁明显凹陷关节面的出现情况。详细介绍了这种特征，为此引入了“外侧滑车”这一术语，它可能代表了一个高级类群的衍征，该类群包括水鸟总目（潜鸟目、鹱形目、鲣鸟目、鹈形目及相关类群）、鹲形类（热带鸟、日鳽和鹭鹤）、红鹳目（火烈鸟和䴙䴘）以及鹤形目（鹤及相关类群）。与许多其他形态特征一样，外侧滑车的出现显示出同形现象。然而，至少一项序列数据分析发现了一个包括上述四个分类群的分支，其相互关系在其他研究中尚未得到最终解决。外侧滑车存在于具有不同颅骨形态和取食适应方式的鸟类中，因此它的出现似乎往往具有系统发育（共同祖先）而非功能起源。方骨内侧髁的形态也可能与一些化石分类群的亲缘关系有关，比如始新世早期的鱼鸟科和梅塞尔鸟科，它们也存在外侧滑车。
