Heterochrony describes acceleration, displacement, and/or retardation of descendants’ development events compared with ancestral states and has often been cited as an important process to bring about morphological novelty. It was coined one-and-a-half centuries ago and has been discussed by both paleobiologists and biologists frequently ever since. Many types of fossil organisms preserve aspects of their development histories in their bones or shells that have been used for heterochrony analyses, with body size being used as a developmental age indicator, despite questions being raised regarding this practice. For organisms whose hard structures consist of multiple chambers, or that contain growth lines, age information suggested by these structures independently can facilitate ontogenetic modeling. In this way, relations among size, shape, and age can be established to document patterns of morphological development.Morphological analysis of pseudoschwagerine fusulinids, a fossil foraminifera group that developed a morphologically novel spherical shell, along with their presumptive triticitid ancestors illustrates this approach to heterochrony analysis. Ontogenetic trajectory comparisons of four major pseudoschwagerine genera, as well as those of triticitids, document relations between their shapes, sizes, and developmental ages. A complex of heterochronic patterns, including peramorphic predisplacement, hypermorphosis, and acceleration, characterize pseudoschwagerine development and appear to be responsible for the novel appearance of large, inflated fusiform and spherical tests in these late Paleozoic benthic foraminifera. The morphometric approach employed in this investigation could be applied widely in the quantitative morphological studies of development histories in a variety of other fossil groups.

中文翻译：

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晚古生代球状梭形有孔虫的异时起源

异时性描述了与祖先状态相比后代发育事件的加速、位移和/或延迟，并且经常被引用为带来形态新颖性的重要过程。它是在一个半世纪前创造出来的，从那时起古生物学家和生物学家就经常讨论它。许多类型的化石生物在其骨骼或贝壳中保留了其发育历史的各个方面，这些方面已用于异时性分析，体型被用作发育年龄指标，尽管对这种做法提出了质疑。对于硬结构由多个腔室组成或包含生长线的生物体，这些结构独立建议的年龄信息可以促进个体发育建模。这样，大小、形状、可以确定年龄和年龄以记录形态发育的模式。pseudoschwagerine fusulinids 的形态学分析是一种化石有孔虫类群，它形成了一种形态新颖的球壳，以及它们推定的 triticitid 祖先，说明了这种异时性分析方法。四个主要的假施瓦格林属以及小麦属的个体发育轨迹比较，记录了它们的形状、大小和发育年龄之间的关系。一种复杂的异时模式，包括变形前位移、变形和加速，是假施瓦格林发育的特征，并且似乎是这些晚古生代底栖有孔虫中大型、膨胀的梭形和球形试验的新外观的原因。