Skeletal resorption – the physiological removal of mineralised parts by an organism – is an important morphogenetic process in bryozoans. Reports of its occurrence and function across the phylum are patchy, however, and have not previously been synthesised. Here we show that resorption occurs routinely across a wide range of bryozoan clades, colony sizes, growth forms, ontogenetic stages, body wall types, skeletal ultrastructures and mineralogies. Beginning in the early Paleozoic, different modes and functions of resorption have evolved convergently among disparate groups, highlighting its utility as a morphogenetic mode in this phylum. Its functions include branch renovation, formation of branch articulations, excavation of reproductive chambers, part‐shedding, and creation of access portals for budding beyond previously formed skeletal walls. Bryozoan skeletons can be altered by resorption at microscopic, zooidal and colony‐wide scales, typically with a fine degree of control and coordination. We classified resorption patterns in bryozoans according to the morphology and function of the resorption zone (window formation, abscission or excavation), timing within the life of the skeletal element resorbed (primary or secondary), and scale of operation (zooidal or multizooidal). Skeletal resorption is probably greatly underestimated in terms of its utility and role in bryozoan life history, and its prevalence across taxa, especially in fossil forms. It is reported proportionally more frequently in stenolaemates than in gymnolaemates. Some modes of resorption potentially alter or remove the spatial–temporal record of calcification preserved within a skeleton. Consequently, knowledge that resorption has occurred can be relevant for some common applications of skeletal analysis, such as palaeoenvironmental interpretation, or growth and ageing studies. To aid recognition we provide scanning electron microscopy, backscattered electron scanning electron microscopy and transmission electron microscopy examples of skeletal ultrastuctures modified by resorption.

中文翻译：

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苔藓虫的骨骼吸收：发生、功能和识别

骨骼吸收——生物体对矿化部分的生理去除——是苔藓动物的重要形态发生过程。然而，关于它在整个门中的发生和功能的报告是零散的，以前没有被综合过。在这里，我们表明吸收经常发生在广泛的苔藓动物进化枝、菌落大小、生长形式、个体发育阶段、体壁类型、骨骼超微结构和矿物学中。从早古生代开始，不同的吸收模式和功能在不同的群体中逐渐演化，突出了其作为该门形态发生模式的效用。它的功能包括分支修复、分支关节的形成、生殖腔的挖掘、部分脱落以及在先前形成的骨骼壁之外创建出芽的入口。苔藓虫骨骼可以通过在微观、动物和群体范围内的吸收来改变，通常具有良好的控制和协调程度。我们根据吸收带的形态和功能（窗口形成、脱落或挖掘）、骨骼元素在生命周期内吸收的时间（主要或次要）和操作规模（动物或多动物）对苔藓动物的吸收模式进行分类。就其在苔藓动物生活史中的效用和作用而言，骨骼吸收可能被大大低估了，它在整个分类群中的流行，尤其是在化石形式中。在 stenolaemates 中比在gynolaemates 中报告的比例更高。某些吸收模式可能会改变或去除骨骼内保存的钙化的时空记录。最后，已经发生吸收的知识可能与骨骼分析的一些常见应用相关，例如古环境解释或生长和老化研究。为了帮助识别，我们提供了通过吸收修饰的骨骼超微结构的扫描电子显微镜、背散射电子扫描电子显微镜和透射电子显微镜示例。