MINIATURIZATION AND ITS EFFECTS ON CRANIAL MORPHOLOGY IN PLETHODONTID SALAMANDERS, GENUS THORIUS (AMPHIBIA, PLETHODONTIDAE) .2. THE FATE OF THE BRAIN AND SENSE-ORGANS AND THEIR ROLE IN SKULL MORPHOGENESIS AND EVOLUTION
MINIATURIZATION AND ITS EFFECTS ON CRANIAL MORPHOLOGY IN PLETHODONTID SALAMANDERS, GENUS THORIUS (AMPHIBIA, PLETHODONTIDAE) .2. THE FATE OF THE BRAIN AND SENSE-ORGANS AND THEIR ROLE IN SKULL MORPHOGENESIS AND EVOLUTION
复制标题
DOI：
10.1002/jmor.1051770304
复制
发表时间：
1983-01-01
影响因子：
1.5
通讯作者：
HANKEN, J
中科院分区：
文献类型：
--
作者：
HANKEN, J
检查了3个物种的大脑和成对感觉器官的相对大小和排列。Thorius [T. macdozigalli，T. narisovalis和T. pennatulus]，一种微小的陆生蝾螈属，是现存最小的有尾四足动物之一。类似测量的3个相关属的较大的热带（Pseudoeurycea，Chiropterotriton）和温带（Plethodon）蝾螈的代表性物种被用来确定的大脑和感觉器官，伴随着Thorius的头部尺寸减小的演变和它们的关系，在头骨形态的相关变化的总体形态的变化。在成年Thorius中，眼睛、耳囊和大脑的相对大小（在额状面和长度上测量的面积）均大于所有较大属的成年Thorius;鼻囊的相对大小不变或略小。种间比例现象、耳囊、眼和脑大小的负异速生长、鼻囊大小的等长或轻微的正异速生长，所有这些都与头骨长度有关，也是T. narisovalis和拟广囊藻Pseudoeurycea goebeli。Thorius的大脑和眼睛的优势导致这些结构与头部前部的鼻囊之间的接触和重叠更大。这与眼睛和鼻囊的前移位有关，鼻囊现在向前突出到头骨本身;眼睛形状的变化;以及前脑壁的内侧变形。在后方，耳囊的优势已经影响了下颌悬肌的重新定向到完全垂直的位置，这与新存在的向后定向的鳞突和胸四肌起源的移位相关。许多这些变化在颅形态可以简单地解释为机械（物理）之间的相互作用的结果，骨骼，神经和感觉组件在头部发育过程中，在减少的大小。这为神经、感觉和其他软组织在颅骨骨骼形态发生中的作用提供了进一步的证据，并加强了在分析颅骨进化时考虑这些组织的必要性。
Relative size and arrangement of the brain and paired sense organs are examined in 3 spp. of Thorius [T. macdozigalli, T. narisovalis and T. pennatulus], a genus of minute, terrestrial salamanders that are among the smallest extant tailed tetrapods. Analogous measurements of representative species of 3 related genera of larger tropical (Pseudoeurycea, Chiropterotriton) and temperate (Plethodon) salamanders are used to identify changes in gross morphology of the brain and sense organs that accompanied the evolution of decreased head size in Thorius and their relation to associated changes in skull morphology. In adult Thorius, relative size (area measured in frontal plane and length) of the eyes, otic capsules and brain each is greater than in adults of all of the larger genera; relative size of the nasal capsules is unchanged or slightly smaller. Interspecific scaling phenomena, negative allometry of otic capsule, eye and brain size, isometry or slight positive allometry of nasal capsule size, all with respect to skull length, also are characteristic of intraspecific (ontogenetic) comparisons in T. narisovalis and Pseudoeurycea goebeli. Predominance of the brain and eyes in Thorius results in greater contact and overlap among these structures and the nasal capsule in the anterior portion of the head. This is associated with anterior displacement of the eyes and nasal capsules, which now protrude anterior to the skull proper; a change in eye shape; and medial deformation of anterior braincase walls. Posteriorly, predominance of the otic capsules has effected a reorientation of the jaw suspensorium to a fully vertical position that is correlated with the novel presence of a posteriorly directed squamosal process and shift in origin of the quadropectoralis muscle. Many of these changes in cranial morphology may be explained simply as results of mechanical (physical) interactions among the skeletal, nervous and sensory components during head development at reduced size. This provides further evidence of the role of nervous, sensory and other soft tissues in cranial skeletal morphogenesis, and reinforces the need to consider these tissues in analyses of skull evolution.