Abstract The stratified red beds of the Catskill Formation are conspicuous in road cut exposures on the Allegheny Plateau of north-central Pennsylvania. During this field trip we will visit and explore several fossil localities within the Catskill Formation. These sites have been central to recent investigations into the nature of Late Devonian continental ecosystems. By the Late Devonian, forests were widespread within seasonally well-watered depositional basins and the spread of plants on land from the late Silurian through the Devonian set the stage for the radiation of animals in both freshwater and terrestrial settings. A diverse assemblage of flora and fauna has been recovered from the Catskill Formation including progymnosperms, lycopsids, spermatophytes, zygopterid and stauripterid ferns, barinophytes, invertebrates and invertebrate traces, and vertebrates such as placoderms, acanthodians, chondrichthyans, actinopterygians, and a variety of sarcopterygians including early tetrapods. Since the early 1990s, highway construction projects along the Route 15 (Interstate 99) have provided a new opportunity for exploration of the Catskill Formation in Lycoming and Tioga counties. The faunas along Route 15 are dominated by Bothriolepis sp. and Holoptychius sp. and also include Sauripterus taylori and an assortment of other interesting records. The most productive Catskill site, and the source of early tetrapod remains, is Red Hill in Clinton County. Red Hill presents a diverse and unique flora and fauna that is distinct from Route 15 sites, and also provides a spectacular section of the alluvial plain deposits of the Duncannon Member of the Catskill Formation.

The Late Devonian Red Hill locality in north-central Pennsylvania contains an Archaeopteris -dominated plant fossil assemblage, a diverse fossil fauna, and an extensive sedimentary sequence ideal for investigating the landscapes and biotic associations of the earliest forest ecosystems. Sedimentological analysis of the main plant-fossil bearing layer at Red Hill indicates that it was a flood-plain pond. A seasonal wet-and-dry climate is indicated by well-developed paleovertisols. The presence of charcoal interspersed with plant fossils indicates that fires occurred in this landscape. Fires appear to have primarily affected the fern Rhacophyton . The specificity of the fires, the distribution profile of the plant remains deposited in the pond, and additional taphonomic evidence all support a model of niche partitioning of the Late Devonian landscape by plants at a high taxonomic level. At Red Hill, Archaeopteris was growing on the well-drained areas; Rhacophyton was growing in widespread monotypic stands; cormose lycopsids grew along the pond edge; and gymnosperms and Gillespiea were possibly opportunists following disturbances. Tetrapod fossils have been described from Red Hill—therefore, this paleoecological analysis is the first systematic interpretation of a specific site that reflects the type of wetland environment within which the earliest tetrapods evolved.