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

The Brechin Lagerstatte of southern Ontario contains an exceptionally diverse and well-preserved Late Ordovician (Katian) crinoid fauna. We describe four genera and eight species of camerate crinoids from the Brechin Lagerstatte, 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 include the diplobathridPararchaeocrinus kiddinew species and the monobathridsGlyptocrinus ramulosusBillings, 1856,Periglyptocrinus priscus(Billings, 1857a),Periglyptocrinus astricusnew species,Periglyptocrinus kevinbrettinew species,Periglyptocrinus mcdonaldinew species,Periglyptocrinus silvosusnew species, andAbludoglyptocrinus steinheimeraenew species. We summarize the taxonomic composition, diversity, and abundance distribution of all known crinoids from the Brechin Lagerstatte 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 found that community structure of the Brechin Lagerstatte is best explained by an ecologically 'complex' RAD model, which suggests that species partitioned niches along multiple resource axes and/or the presence of multiple ecological ways of life. These results indicate that the Brechin Lagerstatte 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. UUID:http://zoobank.org/f86582ed-5db6-469E-befe-34b801f9a113