SORTING THROUGH A PARAPHYLETIC GARBAGE CAN: A PHYLOGENETIC ANALYSIS OF MIDDLE AND UPPER ORDOVICIAN "ENCRINUOIDES" (TRILOBITA) SPECIES FROM LAURENTIAN NORTH AMERICA

The trilobite genus Encrinuroides Reed, 1931 (Subfamily Encrinurinae) has been reported widely from Middle and Upper Ordovician strata of Laurentia, but doubts regarding monophyly surfaced more than 20 years ago. An early phylogenetic analyses by Lespérance and Desbiens identified three new genera, Walencrinuroides, Frencrinuroides, and Physemataspis within "Encrinuroides". However, subsequent analyses by other workers found little support for these groupings, and phylogenetic relationships among species of "Encrinuroides" remain problematic. We attempted to resolve these problems through study of new and type material, including the type species of Frencrinuroides and Walencrinuroides, and also by reanalyzing character selection of previous authors. The ingroup for the analysis included 15 well-documented species, 13 of which were included in previous analyses. We assembled a matrix of 26 characters, 12 of which were complied from previous studies and 14 of which are new. We rooted the trees with "Encrinuroides" regularis Parnaste, which is apparently the oldest encrinurine and has been documented thoroughly in recent work. Parsimony analysis was performed in PAUP 4.0b10 and TNT v.1.1; character optimization employed PAUP* and Winclada v.1.00.08. The results identified three clades that correspond broadly to Walencrinuroides, Frencrinuroides, and Physemataspis. However, although there is some support for the classification proposed by Lésperance and Desbiens, several species in the ingroup are of uncertain status. Our study should therefore be viewed as an interim step that provides provisional diagnoses of these encrinurine genera. Future work will build on these results by restudying poorly known species that are housed in institutions in Britain and Europe.