EVOLUTION OF THE TRILOBITE SUBFAMILY PROETINAE SALTER, 1864, AND THE ORIGIN, DIVERSIFICATION, EVOLUTIONARY AFFINITY, AND EXTINCTION OF THE MIDDLE DEVONIAN PROETID FAUNA OF EASTERN NORTH-AMERICA

This study considers the biogeographic origins, evolutionary affinitie s, and patterns of diversification and extinction in a portion of the Lower and Middle Devonian proetid trilobite fauna of Eastern North Ame rica. Four generic clades comprising about 45 species are known from t he strata of the upper Emsian (Sawkillian) Bois Blanc Limestone and Sc hoharie Grit, the Eifelian (Southwoodian) Onondaga Limestone, and the Givetian (Cazenovian, Tioughniogan, Taghanic) Hamilton Group. These ta xa have traditionally been assigned to the subfamilies Proetinae Salte r, 1864, and/or Dechenellinae Pribyl, 1946. These are Crassiproetus St umm, 1953a, Basidechenella Richter, 1912, Dechenella Kayser, 1880, and Monodechenella Stumm, 1953a, which were originally considered to be c losely related. A higher-level phylogenetic analysis of the Proetinae is conducted to see if these taxa were indeed closely related and thus represent a single endemic radiation of species in Eastern North Amer ica or rather a series of independent lineages in that region. In the course of discerning characters that defined the Proetinae, it was dis covered that Monodechenella lacks several of the characters that defin e the Proetinae, and the members of this genus therefore must be exclu ded from this subfamily. They instead appear to belong to a larger gro up informally referred to as the ''Thebanaspis clade,'' which appears to be closely related to the Proetinae. A phylogenetic analysis is per formed on proetine ingroup taxa using 21 taxa and 53 characters, and s everal of the major generic clades in the Proetinae are considered. Th e phylogenetic analysis of the Proetinae is used to ascertain the ance stral biogeographic states for the three genera in the Proetinae that form an important component of the Lower and Middle Devonian trilobite fauna of Eastern North America. This information is used to determine if these taxa are ancestrally present in Eastern North America or rat her represent a series of invasions from other biogeographic regions. Other taxa occurring in Eastern North America at this time appear to r epresent elements that invaded from Armorica. This invasion of taxa ha s been related to the collision between plates that produced the Acadi an Orogeny during the Middle Devonian. Patterns in these proetid taxa are compared with those known for other groups to ascertain what contr ol the Acadian Orogeny as a biogeographic event may have had on the ap pearance of these taxa in Eastern North America. Phylogenetic analysis is then performed on all available species in each of these generic c lades that occur in Eastern North America. Species that belong to thes e clades but which hail from other biogeographic regions are also cons idered. These phylogenies were used to assess macroevolutionary patter ns such as diversification and extinction within each of these clades in Eastern North America. In addition to being an important paleogeogr aphic event, the Acadian Orogeny also caused major paleoenvironmental changes. The impact of these changes on the proetid fauna of Eastern N orth America is assessed. It appears that a phenomenon analogous to Vr ba's (1985, 1992) Turnover Pulse Hypothesis may have mediated elevated speciation rates in the proetid taxa over the period considered. Howe ver, eventually the profound changes in environment appear to have led to the extinction of much of the proetid trilobite fauna of Eastern N orth America. Information on patterns of occurrence in different geogr aphic regions is combined with information from the phylogenetic analy ses of the individual generic clades to consider large-scale biogeogra phic patterns in the late Lower and Middle Devonian. A method for cons idering biogeographic patterns using cladistic information is develope d. This method is based on Brooks Parsimony Analysis, but it allows mu ltiple events of range expansion and subsequent vicariant splitting to occur within each generic clade. This biogeographic method was used t o evaluate the relationships between the Arctic, Armorican, and Easter n North American paleobiogeographic regions. The relationships between the different major sedimentary basins in Eastern North America, the Appalachian, Illinois, and Michigan basins, are also considered. Final ly, the origin of major evolutionary faunas in the fossil record is di scussed. Included is a brief discussion of a depauperate proetid fauna of the Emsian and Eifelian whose members do not belong to the four ge neric clades considered in detail. In this work four new genera are re cognized: Plesiowensus, Arcticormistonia, Aayemenaytcheia, and Milesda vis. In addition, 12 new species are described: Arcticormistonia edgec ombei, Crassiproetus halliturgidus, C. neoturgidus, C. stummi, C. scho hariensis, Basidechenella cartwrightae, B. timwhitei, Dechenella persc heii, D. carvalhoae, Pedinodechenella modelli, Milesdavis eldredgei, a nd Monodechenella legrandsmithi. Diagnoses and discussions for all of the taxa considered are presented.