Ontogeny of the Upper Cambrian (Furongian) Olenid trilobite Protopeltura aciculate (Angelin, 1854) from Skane and Vastergotland, Sweden
Ontogeny of the Upper Cambrian (Furongian) Olenid trilobite Protopeltura aciculate (Angelin, 1854) from Skane and Vastergotland, Sweden
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DOI：
10.1111/j.1475-4983.2012.01162.x
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发表时间：
2012-07-01
期刊：
影响因子：
2.6
通讯作者：
Clarkson, Euan N. K.
中科院分区：
文献类型：
--
作者：
Mansson, Kristina;Clarkson, Euan N. K.
根据瑞典Andrarum（Skane）和Hjelmsater（Vastergotland）的上寒武统（Furongian）的材料，描述了三叶虫Protopeltura aciculata（Angelin，1854）的个体发育。尖叶拟谷盗分布于Parabolina brevispina和Parabolina spinulosa带。针形原盾虫的所有生长阶段都有，从早期的原盾虫到全盾虫，尽管大多数标本都是脱节的，精确的程度也是未知的。因此，颅被分配到五个形态组。颅骨的表皮雕刻在整个个体发育过程中不断变化。大结节出现在早期阶段，在中期meraspid阶段逐渐消失，并被一个非常微弱的肉芽所取代。在早期meraspid中，短暂的臀板相对较大，呈盾形，边缘刺向上和向后指向，后来变得非常小，三角形，缺乏刺作为晚期meraspid和holaspid。文中还描述了下口类和唇殖类的发育。Protopeltura aciculata在整个发育过程中表现出主要的种内变异，特别是关于pygidium，其中的变异比许多其他olenids少得多。这种高度的发育可塑性可能是生活在压力环境中的三叶虫的生存策略。原化石栖息在一个缺氧的环境中，可能异常地容易局部扩散缺氧或有毒的水。有些变种可能比其他变种更不容易受到这种压力的影响，侥幸存活下来，从而使物种得以延续。
The ontogeny of the trilobite Protopeltura aciculata (Angelin, 1854) is described on the basis of material from the upper Cambrian (Furongian) of Andrarum (Skane) and Hjelmsater (Vastergotland), Sweden. P.aciculata is present in the Parabolina brevispina and Parabolina spinulosa zones. Protopeltura aciculata is represented by all stages of growth, from early protaspides to holaspides, although most of the specimens are disarticulated and precise degrees are unknown. The cranidia have therefore been allocated to five morphological groups. Cuticular sculpture of the cranidia changes throughout ontogeny. Large tubercles are present in earlier stages, disappear gradually in middle meraspid stages and are replaced with a very faint granulation. The transitory pygidium, relatively large and shield-shaped with upwardly and backwardly directed marginal spines in early meraspides, later becomes very small, triangular-shaped and lacking spines as a late meraspid and holaspid. The development of hypostomes and librigenae is also described. Protopeltura aciculata shows major intraspecific variations throughout development, especially regarding the pygidium where variation is much less constrained than in many other olenids. This high developmental plasticity may be a survival strategy for a trilobite living in a stressed environment. Protopeltura inhabited a dysoxic environment, possibly unusually prone to localised spreading of anoxic or toxic water. Some morphs may have been less vulnerable than others to such stresses, surviving by chance and thus enabling the species to continue.