Morphological evolution during the last hurrah of the trilobites: Morphometric analysis of the Devonian asteropyginid trilobites

The Asteropyginae Delo, 1935, is a group of phacopide trilobites in the family Acastidae Delo, 1935, that has served as the focus for several studies due to their distinctive morphologies and diversity. However, despite an interest in these characteristic morphologies, there have been very few studies that have examined this group using morphometric techniques. In this study, we have utilized both geometric morphometric and elliptical Fourier (EF) methods to quantify the morphology of cephalic sclerites of specimens representing a wide taxonomic sampling of the clade. We constructed a phylomorphospace that shows temporal and spatial patterns of phenotypic evolution within the framework of an updated tip-dated phylogenetic tree generated using Bayesian inference. Of particular note was the recovery of similar patterns, regardless of the morphometric approach. These further illustrated that there were marked expansions into morphospace throughout the temporal range of the clade. This study highlights the utility of employing different methodologies to quantitatively explore the disparity of fossil taxa. It also illustrates some of the patterns of morphologic change occurring during one of the final and major evolutionary radiations within Phacopida.Funding provided by: University of KansasCrossref Funder Registry ID: http://dx.doi.org/10.13039/100007859Award Number: Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: DBI 160206