Paleocommunity composition, relative abundance, and new camerate crinoids from the Brechin Lagerstätte (Upper Ordovician)

The Brechin Lagerstätte of southern Ontario contains an exceptionally diverse and well-preserved Late Ordovician (Katian) crinoid fauna. Here, we describe four genera and eight species of camerate crinoids from the Brechin Lagerstätte, including six new species. Consequently, the total diversity of the fauna now stands at 27 genera and 39 nominal species, thereby making it the most taxonomically diverse Ordovician crinoid fauna known. Taxa described herein include the diplobathrid Pararchaeocrinus kiddi n. sp. and the monobathrids Glyptocrinus ramulosus, Periglyptocrinus priscus, Periglyptocrinus astricus n. sp., Periglyptocrinus kevinbretti n. sp., Periglyptocrinus mcdonaldi n. sp., Periglyptocrinus silvosus n. sp., and Abludoglyptocrinus steinheimerae n. sp. We summarize the taxonomic composition, diversity, and abundance distribution of all known crinoids from the Brechin Lagerstätte to better characterize the paleoecological structure and complexity of the community. We establish that the fauna is dominated by the subclass Pentacrinoidea, both in terms of abundance and species richness. In addition, we analyze species-level abundance data using relative abundance distribution (RAD) models to evaluate the ecological complexity of the paleocommunity. We find that community structure of the Brechin Lagerstätte is best explained by an ecologically “complex” RAD model, which suggests species partitioned niches along multiple resource axes and/or the presence of multiple ecological ways of life. These results indicate that the Brechin Lagerstätte is significant not only for being the most taxonomically diverse Katian crinoid assemblage, but also for being an early ecologically complex fauna that developed in the wake of the Great Ordovician Biodiversification Event.

安大略南部的布雷钦特异埋藏化石库（Brechin Lagerstätte）产出了物种多样性极高且保存状态极佳的晚奥陶世凯迪期（Katian）海百合化石群。本研究记述了该化石库中包海百合亚纲（Camerata）海百合类的4属8种，其中包含6个新种。至此，该化石群的总分类多样性已达27属39个命名种，使其成为已知分类学多样性最高的奥陶纪海百合化石群。本次记述的类群包括双柱海百合亚目（diplobathrid）的帕拉始海百合属（Pararchaeocrinus）基迪新种（n. sp.），以及单柱海百合亚目（monobathrid）的雕海百合属（Glyptocrinus ramulosus）、近雕海百合属（Periglyptocrinus priscus）、近雕海百合属（Periglyptocrinus astricus）新种（n. sp.）、近雕海百合属（Periglyptocrinus kevinbretti）新种（n. sp.）、近雕海百合属（Periglyptocrinus mcdonaldi）新种（n. sp.）、近雕海百合属（Periglyptocrinus silvosus）新种（n. sp.），以及阿布卢德雕海百合属（Abludoglyptocrinus steinheimerae）新种（n. sp.）。我们汇总了布雷钦特异埋藏化石库中所有已知海百合的分类组成、多样性及丰度分布特征，以更好地解析该古群落的古生态结构与复杂性。研究证实，无论在丰度还是物种丰富度层面，该化石群均以五列海百合亚纲（Pentacrinoidea）为主导类群。此外，我们采用相对丰度分布（relative abundance distribution, RAD）模型对物种级丰度数据开展分析，以评估该古群落的生态复杂性。研究结果显示，布雷钦特异埋藏化石库的群落结构最符合生态意义上的"complex" RAD模型，这表明物种在多个资源轴上分化出生态位，或存在多种不同的生态生活方式。本研究结果表明，布雷钦特异埋藏化石库不仅是已知分类学多样性最高的凯迪期海百合组合，同时也是奥陶纪生物大辐射事件（Great Ordovician Biodiversification Event）之后形成的早期生态复杂型化石群，具有重要的科研价值。