Revisiting the Cambrian Series 1 animal origination chronology

最古老的贝壳海洋生物出现在约5.4亿年前的寒武纪大爆发中。这项研究试图完善这一引人入胜的进化事件的时间表。这项任务比预期的要难，因为同一生物体的化石在不同的时间出现在不同的地方。寒武纪海洋沉积物沉积和化石产状的年表稀疏，如何才能分辨出同一物种的许多化石中哪些是最古老的，并完善其进化时间表？这项研究使用计算机程序来匹配保存在寒武纪化石所在岩石中的碳循环变化的全球同步化学信号。将化石所在位置的化学信号与寒武纪多个年代的化学信号进行匹配，可以通过外推确定这些年龄。由于大多数寒武纪化石生物是静止的分类门中最早的成员，我们的研究促进了对动物支系内部和之间进化节奏的科学研究的进展。该项目将为更广泛的地质界开发开放源码的互动软件，以便在不需要高级编码经验的情况下调整化学记录；培训一名博士生和三名本科生进行计算研究；并基于这一新软件开发和分发课程，以促进本科生的量化素养。早寒武纪小型骨骼化石的辐射年表来自于δ13Ccarb在摩洛哥U-Pb放射性校准的贫瘠化石地层剖面的视觉排列，到其他地方化石丰富、时间不确定的剖面的偏移。Visualδ13Ccarb关联方法不能确保唯一对齐，也不能确保给定的年表。这项研究采用动态规划算法来识别化石地层剖面和摩洛哥δ13Ccarb-U/Pb年龄模型之间的地质允许对齐库。每个允许的δ13Ccarb排列将为地层剖面上所有化石分类群的局部首次出现基准(FAD)生成不同的年表，因此，本地FAD年表的各种组合将为分类群的全球FAD产生不同的年龄。这项拟议的研究探索了替代的全球FAD年代学是否/如何揭示了不同数量的起源脉冲以及脉冲起始和持续时间的替代年龄，从而解决了迄今为止在最早的寒武纪爆炸年代学中尚未被承认的不确定性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The oldest shelly sea creatures appeared ~540 million years ago in the ‘Cambrian explosion’. This research seeks to refine the timeline for this captivating evolutionary event. This task is harder than expected because fossils of the same organism appear at different times in different places. How can one tell which of the many fossils of the same species is oldest—and refine its evolutionary timeline—with a sparse chronology for Cambrian marine sediment deposition and fossil occurrences? This research uses a computer program to match up the globally synchronous chemical signals of carbon cycle changes preserved in the rocks hosting Cambrian fossils. Matching the chemical signals from a fossil’s location to the one Cambrian location with many dates will allow these ages to be determined via extrapolation. As most Cambrian fossil organisms are the earliest members of still-living taxonomic phyla, our research promotes the progress of scientific inquiry into the tempo of evolution within and across animal clades. This project will develop open source, interactive software for the broader geological community to align chemical records without the need for advanced coding experience; train one PhD student and three undergraduates in computational research; and develop and distribute curricula, based on this new software, to promote undergraduate quantitative literacy. The chronology for the early Cambrian radiation of small skeletal fossils arises from visual alignment of δ13Ccarb excursions at a U-Pb radiometrically calibrated, fossil barren, stratigraphic section in Morocco to excursions at richly fossiliferous, time uncertain sections elsewhere. Visual δ13Ccarb correlation methods cannot ensure unique alignments, nor a given chronology. This research adopts a dynamic programming algorithm to identify libraries of geologically permissible alignments between fossiliferous stratigraphic sections and the Moroccan δ13Ccarb–U/Pb age model. Each permissible δ13Ccarb alignment will generate a distinct chronology for the local first appearance datum (FAD) of all fossil taxa at a stratigraphic section and, thus, various combinations of local FAD chronologies will yield alternative ages for a taxon’s global FAD. The proposed research explores whether/how alternative global FAD chronologies reveal a different number of origination pulses and alternative ages for pulse initiation and duration, thereby addressing heretofore unacknowledged uncertainty in the earliest Cambrian explosion chronology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.