Abstract

Acipenseriformes (Actinopterygii) are commonly recognized as a sister group of Neopterygii. They represent the basal-most taxa of extant ray-finned fishes, along with Polypterus (Polypteriformes). This position on the cladogram determines the key importance of sturgeons for an understanding of the evolutionary history of actinopterygians, as well as bony fishes in general. However, their unique morphology and the absence of any reliable homologies (in particular, for the snout region and jaw arch) make these fishes ineffective for the testing of phylogenetic hypotheses and the reconstruction of the evolution of Osteichthyes. This article presents the results of a comparative anatomical analysis of the jaw arch and snout region in sturgeons. The homologies of these parts are established, and an evolutionary scenario is proposed to explain the transformation of the mandibular arch and snout region during the presumed transition from palaeoniscoid ancestors to Acipenseriformes. It is shown that these transformations were triggered by paedomorphosis, which caused, inter alia, underdevelopment of the lower jaw. This underdevelopment resulted in a release of the anterior ends of the upper jaw rami and the entire snout region from restrictions concerning the functioning of the jaw apparatus.

中文翻译：

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Paedomorphosis在头足类动物（Actinopterygii）头骨Bauplan的出现中的作用

摘要

Acipenseriformes（Actinopterygii）通常被认为是Neopterygii的姐妹群体。它们代表了现存射线鳍鱼类的最基础分类群，以及Poly属鱼类（多形体）。分支图上的这个位置决定了st鱼对于了解放线翅目以及一般鱼类的进化史的关键重要性。然而，它们的独特形态和缺乏任何可靠的同源性（特别是对于鼻子区域和颚弓），使得这些鱼类无法有效地用于系统发育假设的测试和对鱼类的重建。本文介绍了st鱼颌骨弓和鼻部区域的比较解剖分析结果。建立了这些部分的同源性，并提出了一种进化方案来解释在假定的从古黏性祖先到A形过渡期间下颌弓和鼻子区域的转变。结果表明，这些转变是由多形畸形引起的，其尤其导致下颌的发育不足。这种欠发达导致上颚钳口的前端和整个口鼻部区域脱离了下颚装置功能的限制。