The most ventral muscles of the head (the mm. submentalis, intermandibularis, and interhyoideus) provide support to the gular region and lift the buccal floor during ventilation and feeding. These muscles show limited variation in most gnathostomes, but in Anura they exhibit a surprising diversity. The few studies that have explored this character system highlighted its potential as a source of phylogenetic information. In this paper we explored the diversity of this character system studying specimens of 567 anuran species and reviewing published data to cover a total of 1321 species, belonging to 53 of the 54 currently recognized anuran families, as well as caudates and caecilians. We defined 27 discrete characters including the number of muscle bellies, supplementary layers, hypertrophy and diversity of elastic fibres, and pigmentation, among others, and optimized them on a comprehensive phylogenetic hypothesis. We recognized 223 unambiguously optimized synapomorphies for numerous clades on different scales, including three for Anura and many for suprafamiliar clades with poor phenotypic support. Finally, we discussed the evolution of this highly diverse character system, including homology, development, and its functional role in vocalization and feeding. Interestingly, the striking levels of variation in some structures contrast with the amount of phylogenetic inertia, allowing us to recognize several general patterns. Supplementary elements of the m. intermandibularis evolved first as broad layers occuring in more than half of extant anuran species and then concentrated forming discreet bellies in several clades. The anterior portion of the gular region is not sexually dimorphic, and is likely related to ventilation and tongue protraction. Conversely, the diversity of the m. interhyoideus is strongly linked to vocal sacs, which are present only in adult males, suggesting the presence of two independent modules.

中文翻译：

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Anura 明显多样化的下颌下肌的进化

头部最腹侧的肌肉（颏下肌、下颌间肌和舌骨间肌）) 在通风和喂食期间为牙龈区域提供支撑并提升颊底。这些肌肉在大多数有颚类动物中表现出有限的变化，但在 Anura 中，它们表现出令人惊讶的多样性。探索这一特征系统的少数研究强调了它作为系统发育信息来源的潜力。在本文中，我们探索了该特征系统的多样性，研究了 567 种无尾目物种的标本，并回顾了已发表的数据，共涵盖 1321 个物种，属于目前公认的 54 个无尾目亚目科中的 53 个，以及尾状目和盲尾目。我们定义了 27 个离散特征，包括肌肉腹部的数量、补充层数、弹性纤维的肥大和多样性以及色素沉着等，并根据全面的系统发育假设对其进行了优化。我们识别出 223 个针对不同尺度上众多进化枝的明确优化的突触，包括三个用于 Anura 和许多用于表型支持较差的超熟悉进化枝。最后，我们讨论了这种高度多样化的字符系统的演变，包括同源性、发育及其在发声和喂养中的功能作用。有趣的是，某些结构的显着变异水平与系统发育惯性的量形成对比，使我们能够识别几种一般模式。m的补充元素。及其在发声和进食中的功能作用。有趣的是，某些结构的显着变异水平与系统发育惯性的量形成对比，使我们能够识别几种一般模式。m的补充元素。及其在发声和进食中的功能作用。有趣的是，某些结构的显着变异水平与系统发育惯性的量形成对比，使我们能够识别几种一般模式。m的补充元素。intermandibularis首先进化为广泛的层，出现在超过一半的现存anuran物种中，然后在几个进化枝中集中形成谨慎的腹部。眼区的前部不是两性异形的，可能与通气和舌头前伸有关。相反，m的多样性。interhyoideus与声囊密切相关，声囊仅存在于成年男性中，这表明存在两个独立的模块。