TRIGONOTARBID DIVERSITY OF NORTH AMERICA

Trigonotarbids are ancient, spider-like arachnids and represent some of the earliest fully terrestrial animals. Their fossils are found in late Silurian to early Permian deposits and occur in both North America and Europe but most trigonotarbid research has been conducted on European examples. Many trigonotarbid fossils from North America have either not been described fully or remain undescribed. The lack of research on North American trigonotarbids presents a great potential for expanding our understanding of Trigonotarbida with respect to biogeography, taxonomy, and phylogenetics. Currently there are nearly twice as many families and more than three times as many genera of trigonotarbids represented in Europe compared to North America. Here, trigonotarbids from several North American deposits are revisited and described for the first time in order to explore the diversity and evolutionary history of the group and identify the potential impacts on phylogenetic reconstructions of Trigonotarbida. In terms of species richness, composition, and abundance, I hypothesize that North American Trigonotarbida diversity is similar to Europe due to their close paleogeography. Trigonotarbids in this study come from 12 localities including Illinois, New York, Pennsylvania, Kansas, New Brunswick, New Mexico, and others, all of which are middle Devonian through late Pennsylvanian in age. Specimens are held in collections at several national institutions. Examination of North American trigonotarbid specimens has shown the high likelihood of trigonotarbid species that have yet to be described in North American. There are currently over a dozen specimens from multiple localities in museum collections that have only been described down to their order, yet many likely have sufficient diagnostic characters to be identified further (this includes some of the most complete specimens). Trigonotarbids are crucial to both understanding the origins of terrestrial arthropods and expanding our knowledge on the overall evolutionary history of life. The implications from this project include remedying a major gap in the arachnid fossil record, revealing patterns in diversity after the colonization of land, improving phylogentic trees, and possibly showing the impact mass extinctions had on early terrestrial animals.