Heterochrony has played a key role in the evolution of invertebrate larval types, producing “head larvae” in diverse taxa, where anterior structures are accelerated and specialized at the expense of more caudal ones. For chordates, judging from amphioxus, the pattern has been more one of repeated acceleration of adult features so that they function earlier in development, thus converting the ancestral larva, whether it was a head larva or not, into something progressively more chordate-like. Recent molecular data on gene expression patterns in the anterior nerve cord of amphioxus point to a similar process being involved in the origin of the telencephalon. As vertebrates evolved, a combination of acceleration and increasing egg size appears here to have allowed the development of a structure that would originally have emerged only gradually in the post-embryonic phase of the life history to be compressed into embryogenesis. The question then is what, in functional terms, makes the telencephalon so important to the survival of post-embryonic ancestral vertebrates that this was adaptively advantageous. A better understanding of the function this brain region performs in amphioxus may help provide the answer.

中文翻译：

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通过异质性进行创新：两栖动物对端脑起源和功能的看法

异时性在无脊椎动物幼体类型的进化中发挥了关键作用，在不同的类群中产生“头状幼虫”，其中前部结构被加速和专门化，而尾状结构则以更多为代价。从双栖动物来看，对脊索动物来说，这种模式更多地是成年特征反复加速的一种特征，这样它们就可以在发育早期发挥作用，从而将祖先的幼虫（无论它是否是头部幼虫）转变为逐渐类似于氯酸盐的东西。最近有关双歧杆菌前神经索中基因表达模式的分子数据表明，端脑的起源涉及一个类似的过程。随着脊椎动物的进化，加速和增加卵子大小的结合在这里似乎使原本只能在生命史的胚胎后阶段逐渐出现并被压缩为胚胎发生的结构得以发展。然后的问题是，从功能上讲，是什么使远脑对胚胎后祖先的脊椎动物的生存如此重要，以至于它在适应性上是有利的。更好地了解此大脑区域在两栖动物中的功能可能有助于提供答案。