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首页> 外文学位 >Modeling the Size Frequency Distributions of the Trilobite Aulacopleura koninckii and its Implications for Understanding Trilobite Biology and Preservation Potential.
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Modeling the Size Frequency Distributions of the Trilobite Aulacopleura koninckii and its Implications for Understanding Trilobite Biology and Preservation Potential.

机译：对三叶虫Aulacopleura koninckii的大小频率分布进行建模及其对理解三叶虫生物学和保存潜力的启示。

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摘要

Trilobites were a diverse group of Paleozoic marine arthropods, whose growth is characterized by exoskeletal ecdysis; molting of the outer cuticle. If all sclerites from all growth stages were preserved in a fossil assemblage, the distribution would be expected to be strongly right skewed because individuals must have passed through smaller molt stages, but not all small individuals would have survived to large size. However, the overwhelming majority of observed trilobite size frequency distributions have normal size distributions. This thesis investigates this discrepancy using a modified version of the method used by Hartnoll and Bryant (1990) to model crab size frequency distributions. Here I apply this method to the trilobite Aulacopleura koninckii, a Silurian species whose growth is among the best known for any fossil, and for which size-specific assemblages of articulated individuals are observed. This required the use of parameters known for A. koninckii, in combination with other estimates based on living crab biology. Observed growth parameters from A. koninckii suggest that this trilobite underwent up to 33 post-protaspid instars separated by 32 post-protaspid molts. A mortality rate of 10% per instar was assumed based on evidence that this taxon occupied a low predation environment. Given the assumption of constant recruitment and crab-based estimates of X and Y, derived from the observation that intermolt period increased systematically as size increased, I was able to model predicted distributions of A. koninckii sizes that matched the largest individuals observed. Estimated life spans of A. koninckii according to these parameters lie between 1 and 10 years. As expected these distributions predicted far larger numbers of smaller specimens than larger ones, which is not what is observed. To explain the dearth of smaller individuals I accounted for the probability of preservation in order to explore how the size frequency distributions behaved. Simulations suggest that the size frequency distributions observed for A. koninckii could be the outcome of either a preservation bias against smaller trilobites, an event that killed off a live population, or the result of the fact that size frequency distributions have many variables that cannot be determined from the fossil record.
机译：三叶虫是古生代海洋节肢动物的不同种类，其生长特征是骨骼外蜕皮。外角质层蜕皮。如果将来自所有生长阶段的所有巩膜石保存在化石组合中，则由于个人必须经过较小的蜕皮阶段，所以预期该分布会强烈偏斜，但并非所有的小型个体都可以存活到较大的规模。然而，绝大多数观察到的三叶虫大小频率分布具有正常大小分布。本文使用Hartnoll和Bryant（1990）用来模拟螃蟹大小频率分布的方法的改进版本来研究这种差异。在这里，我将这种方法应用于三叶虫Aulacopleura koninckii，一种志留纪物种，其生长是任何化石中最出名的，并且观察到了具关节大小的个体的特定大小的组合。这就需要使用已知的A. koninckii参数，并结合基于活蟹生物学的其他估计。观察到的来自孔氏曲霉的生长参数表明，该三叶虫经历了由33个后蜕皮分离的多达33个前棘后的star。根据证据表明该分类单元占据了低捕食环境，每只鸡的死亡率为10％。假定恒定的补充和基于蟹和蟹的X和Y估计值是从观察到蜕皮期随着大小的增加而系统地增加而得出的，所以我能够对与观察到的最大个体匹配的A. koninckii大小的预测分布进行建模。根据这些参数，估计的柯宁曲霉的寿命在1至10年之间。正如预期的那样，这些分布预测的较小样本的数量将比较大样本的数量大得多，这与观察不到的结果相同。为了解释较小个体的缺乏，我考虑了保存的可能性，以探讨大小频率分布的行为。模拟表明，观察到的A. koninckii的大小频率分布可能是对较小的三叶虫的保存偏见，杀死活种群的事件或以下事实的结果：大小频率分布具有许多无法确定的变量根据化石记录确定。

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  • 作者

    Kolenko, Rachel Lynn.;

  • 作者单位

    University of California, Riverside.;

  • 授予单位 University of California, Riverside.;
  • 学科 Paleontology.;Geology.;Paleoecology.
  • 学位 M.S.
  • 年度 2016
  • 页码 56 p.
  • 总页数 56
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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