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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华南下寒武统三叶虫多丁亚(多丁亚)早后胚期至成熟个体发育(系列2)
DOI：
10.5061/dryad.mb1t9
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发表时间：
2015
影响因子：
2.3
通讯作者：
XI-GUANG ZHANG
中科院分区：
文献类型：
--
作者：
JIN-BO HOU;NIGEL C. HUGHES;TIAN LAN;JIE YANG;XI-GUANG ZHANG
在中国南部贵州省瓮安的早寒武世（第三阶段）明心寺组中发现的许多保存完好的铰接式外骨骼，可以重建小型带头三叶虫多丁亚多丁亚（Duodingia duodingensis Chow）从早期胚胎后到成熟（即原壳到全盾）的个体发育。该模式材料很可能是最新阶段的默拉斯皮斯，并且该物种在长拉斯皮斯阶段有九个胸节，而不是之前建议的八个。最早的holaspis体型相对较小（全长约3.00毫米），随后的龄期几乎没有表现出与体型相关的形状变化。在个体发育早期，眉间的形态发生了显着的变化，包括轴沟向前延伸，直到达到 0iii 级的头前缘，以及眉间中部区域变窄。这是第一个在 0 级内表现出三个发育阶段的非盘科三叶虫。个体发生变化的记录表明，Duodingiahubeiensis 和 D. taihuensis 都是 D. duodingensis 的初级同义词，因为它们具有其高级同义词的特定个体发育阶段的特征。在这种小三叶虫中，多丁D. duodingensis的每次换毛生长增量明显较小。甲藻期躯干分段的发育显然比许多其他三叶虫更为复杂，可能包括个体甲藻程度内的多次蜕皮、节段释放模式的种内多态性或群体之间节段表达程度的表型变异。累积换羽（节段被添加到尾部）和耗尽换羽（节段被释放到胸部）之间的波动如果得到证实，将表明躯干节段发育的这些不同方面之间的紧密协调。
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 midregion. This is the first noneodiscid trilobite to show three developmental stages within meraspid degree 0. Documentation of ontogenetic changes demonstrates that both Duodingiahubeiensis 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 .