|Congreve, Curtis Raymond
|Lieberman, Bruce S.
|Congreve, C. R., and B. S. Lieberman. 2011. Phylogenetic and biogeographic analysis of sphaerexochine trilobites. PloS One 6:e21304. http://dx.doi.org/10.1371/journal.pone.0021304
|Background: Sphaerexochinae is a speciose and widely distributed group of cheirurid trilobites. Their temporal range
extends from the earliest Ordovician through the Silurian, and they survived the end Ordovician mass extinction event (the
second largest mass extinction in Earth history). Prior to this study, the individual evolutionary relationships within the
group had yet to be determined utilizing rigorous phylogenetic methods. Understanding these evolutionary relationships is
important for producing a stable classification of the group, and will be useful in elucidating the effects the end Ordovician
mass extinction had on the evolutionary and biogeographic history of the group.
Methodology/Principal Findings: Cladistic parsimony analysis of cheirurid trilobites assigned to the subfamily
Sphaerexochinae was conducted to evaluate phylogenetic patterns and produce a hypothesis of relationship for the
group. This study utilized the program TNT, and the analysis included thirty-one taxa and thirty-nine characters. The results
of this analysis were then used in a Lieberman-modified Brooks Parsimony Analysis to analyze biogeographic patterns
during the Ordovician-Silurian.
Conclusions/Significance: The genus Sphaerexochus was found to be monophyletic, consisting of two smaller clades (one
composed entirely of Ordovician species and another composed of Silurian and Ordovician species). By contrast, the genus
Kawina was found to be paraphyletic. It is a basal grade that also contains taxa formerly assigned to Cydonocephalus.
Phylogenetic patterns suggest Sphaerexochinae is a relatively distinctive trilobite clade because it appears to have been
largely unaffected by the end Ordovician mass extinction. Finally, the biogeographic analysis yields two major conclusions
about Sphaerexochus biogeography: Bohemia and Avalonia were close enough during the Silurian to exchange taxa; and
during the Ordovician there was dispersal between Eastern Laurentia and the Yangtze block (South China) and between
Eastern Laurentia and Avalonia.
|Support for this research was provided by NSF DEB-0716162. The funders had no role in study design, data collection and analysis, decision to publish,
or preparation of the manuscript.
|2011 Congreve, Lieberman. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
|Phylogenetic and Biogeographic Analysis of Sphaerexochine Trilobites
|Lieberman, Bruce S.
|Ecology and Evolutionary Biology
|Scholarly/refereed, publisher version
|This item meets KU Open Access policy criteria.