Early postembryonic to mature ontogeny of the oryctocephalid trilobite Duodingia duodingensis from the lower Cambrian (Series 2) of southern China
Early postembryonic to mature ontogeny of the oryctocephalid trilobite Duodingia duodingensis from the lower Cambrian (Series 2) of southern China
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DOI：
10.1002/spp2.1021
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发表时间：
2015-11
影响因子：
2.3
通讯作者：
Jin-bo Hou;N. Hughes;Tian Lan;Jie Yang;Xi-guang Zhang
中科院分区：
文献类型：
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作者：
Jin-bo Hou;N. Hughes;Tian Lan;Jie Yang;Xi-guang Zhang
在中国南部贵州省瓮安早寒武世明心寺组（第3阶段）发现的许多保存完好、有关节的外骨骼，允许重建小的oryctocephalid三叶虫Duodingia duodingensis Chow的早期胚后至成熟（即原蝎至全蝎）个体发育。该模式标本很可能是最后阶段的meraspis，并且该物种在holaspid阶段有9个胸节，而不是之前建议的8个。最早期的Holaspis在尺寸上相对较小（全长约3.00 mm），并且随后的龄期几乎没有与尺寸相关的形状变化。在个体发育早期，眉间的形态发生了显著的变化，包括轴向沟向前延伸，直到它们到达0iii度的meraspid的前头部边缘，以及眉间中部区域变窄。这是第一个noneoaduld三叶虫显示在meraspid度0内的三个发育阶段。个体发育变化的研究表明，湖北多丁木和湖北多丁木都是一种重要的植物。taihuensis是D. duodingensis具有其高级异名的特定个体发育阶段的特征。D.在这一小三叶虫中，多丁虫明显较小。在meraspid阶段的树干分割的发展显然是更复杂的比在许多其他三叶虫，可能包括多个蜕皮内的个人meraspid度，种内多态性的模式段释放，或表型变异的人口之间的程度段的表达。累积换羽，其中部分被添加到meraspid pygidium，和消耗换羽，其中部分被释放到胸部之间的波动，如果得到证实，将建议这些不同方面的树干段的发展之间的紧密协调。
Many well‐preserved, articulated exoskeletons recovered from the early Cambrian (Stage 3) Mingxinsi Formation in Weng'an, Guizhou Province, southern China, permit reconstruction of the early postembryonic to mature (i.e. protaspid to holaspid) ontogeny of the small oryctocephalid trilobite Duodingia duodingensis Chow. It is likely that the type material is a latest stage meraspis, and the species had nine thoracic segments in the holaspid phase rather than the eight suggested previously. The earliest holaspis is relatively small in size (about 3.00 mm in total length), and the succeeding instars show little size‐related shape change. Striking changes take place in the morphology of the glabella during early ontogeny including forward extension of the axial furrows until they reach the anterior cephalic margin in meraspid degree 0iii, and narrowing of the glabellar mid‐region. This is the first noneodiscid trilobite to show three developmental stages within meraspid degree 0. Documentation of ontogenetic changes demonstrates that both Duodingia hubeiensis and D. taihuensis are junior synonyms of D. duodingensis because they bear characters of particular ontogenetic stages of their senior synonym. The per‐moult growth increment in D. duodingensis was apparently small in this small trilobite. The development of trunk segmentation during the meraspid phase is apparently more complex than in many other trilobites and could include multiple moults within individual meraspid degrees, intraspecific polymorphism in the pattern of segment release, or phenotypic variation among the population in the degree of segment expression. Fluctuations between accumulative moults, in which segments are added to the meraspid pygidium, and depletive moults, in which segments are released into the thorax, if confirmed, would suggest tight coordination between these different aspects of trunk segment development.