The morphology of Idiocranium russeli (amphibia: Gymnophiona), with comments on miniaturization through heterochrony
The morphology of Idiocranium russeli (amphibia: Gymnophiona), with comments on miniaturization through heterochrony
复制标题
Idiocranium russeli（两栖类：Gymnophiona）的形态，以及通过异时性实现小型化的评论
作者：
M. Wake
特颅龙是最小的无尾目动物之一。头骨的形态（例如，小的，广泛分布的真皮成分，保留软骨残留物）和后椎骨（不完全发育，保留后脊索）表明异时性，或发育时间的变化，导致了该物种的小型化。这种模式显然是一种原生模式，其特征是发育的早期偏移（参见Alberch et al.，1979年）。骨科的其他独特特征（例如，广泛的蝶筛骨发育）与该物种的穴居习性相关，可能是为了补偿前代效应而出现的。肌肉学、神经学和内脏形态学的一些特征也与小型化相关。生殖成熟发生在全长约75 mm时;性腺比例较小，但生殖形态的其他方面是直接发育的盲肠动物的典型特征。
Idiocranium russeli is among the smallest species of caecilians. The morphology of the skull (e.g., small, widely spaced dermal elements, retention of cartilaginous remnants) and of the posterior vertebrae (incomplete development, retention of a postvertebral notochord) indicate that heterochrony, or change in timing of development, has resulted in the miniaturization of the species. The pattern is apparently a progenetic one, characterized by early offset of development (see Alberch et al., 1979). Other unique features of osteology (e.g., extensive sphenethmoid development) correlate with the burrowing habit of the species and may have arisen to compensate for progenetic effects. Several features of the myology, neurology, and visceral morphology are correlated with miniaturization as well. Reproductive maturity occurs at approximately 75 mm total length; gonads are proportionately small, but other aspects of reproductive morphology are typical of direct‐developing caecilians.