Abundant articulated specimens of the oryctocarine trilobite Oryctocarella duyunensis from the lower Cambrian (Stage 4, Series 2) Balang Formation at the Bulin section in western Hunan Province, South China, permit the description of all meraspid degrees. The maximum number of thoracic segments observed in this collection is 11. Meraspid growth was accompanied by progressive and gradual change in overall form, and this animal showed an homonymously segmented trunk with variation in the number of pygidial segments during ontogeny. Such variation permits a variety of plausible explanations, but a model of successive instars defined by the number of thoracic segments, and in suborder by the number of pygidial segments, is highly unlikely to explain the growth pattern because it would result in the loss of trunk segments between some instars. Degree-based ontogenetic staging is compatible with the variation observed.

中文翻译：

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湘西早寒武世三叶虫Oryctocarella duyunensis的发育

丰富的三叶虫关节标本杜云鲇鱼来自华南湖南省西部布林剖面的下寒武统（第 4 期，系列 2）Balang 组，允许描述所有 meraspid 度。在该集合中观察到的最大胸节数为 11。 Meraspid 的生长伴随着整体形态的渐进式和逐渐变化，并且该动物在个体发育过程中表现出同名分段的躯干，其尾节数有所变化。这种变化允许各种似是而非的解释，但由胸节数定义的连续龄期模型，并按尾节数的亚序，极不可能解释生长模式，因为它会导致躯干的丧失一些龄期之间的段。基于度数的个体发育分期与观察到的变异相容。