Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China.
MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China.
Sci Rep. 2019 Apr 5;9(1):5709. doi: 10.1038/s41598-019-41911-w.
Moulting is a fundamental component of the ecdysozoan life cycle, but the fossil record of this strategy is susceptible to preservation biases, making evidence of ecdysis in soft-bodied organisms extremely rare. Here, we report an exceptional specimen of the fuxianhuiid Alacaris mirabilis preserved in the act of moulting from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China. The specimen displays a flattened and wrinkled head shield, inverted overlap of the trunk tergites over the head shield, and duplication of exoskeletal elements including the posterior body margins and telson. We interpret this fossil as a discarded exoskeleton overlying the carcass of an emerging individual. The moulting behaviour of A. mirabilis evokes that of decapods, in which the carapace is separated posteriorly and rotated forward from the body, forming a wide gape for the emerging individual. A. mirabilis illuminates the moult strategy of stem-group Euarthropoda, offers the stratigraphically and phylogenetically earliest direct evidence of ecdysis within total-group Euarthropoda, and represents one of the oldest examples of this growth strategy in the evolution of Ecdysozoa.
蜕皮是节肢动物生命周期的一个基本组成部分，但这种策略的化石记录容易受到保存偏差的影响，因此，软体生物蜕皮的证据极为罕见。在这里，我们报告了一个来自中国南方寒武纪（阶段 3）小石板生物群的非凡标本，即软舌螺类 Alacaris mirabilis，它正在蜕皮。该标本显示出一个扁平且起皱的头部盾牌、身体背板倒叠在头部盾牌上，以及包括后体边缘和尾刺在内的外骨骼元素的重复。我们将这个化石解释为一个废弃的外骨骼，覆盖在一个正在出现的个体的尸体上。A. mirabilis 的蜕皮行为让人联想到十足目动物，在十足目动物中，甲壳质后部分离并从前体旋转，为新出现的个体形成一个宽阔的口。A. mirabilis 揭示了干群节肢动物的蜕皮策略，提供了干群节肢动物中蜕皮的最早的直接化石证据，也是蜕皮这一生长策略在节肢动物演化中最早的例子之一。
