ONTOGENY AND PALEOECOLOGY OF THE MIDDLE PENNSYLVANIAN ARBORESCENT LYCOPOD BOTHRODENDRON PUNCTATUM, BOTHRODENDRACEAE (WESTERN MIDDLE ANTHRACITE FIELD, SHAMOKIN QUADRANGLE, PENNSYLVANIA)

Study of an in situ Bothrodendron punctatum community in a strip mine in Bear Valley, Shamokin Quadrangle, Pennsylvania, provides new insights into the ontogeny of Middle Pennsylvanian arborescent lycopods and into the ecological and environmental characteristics of lycopod‐dominated clastic‐swamp communities. Bothrodendron punctatum began growth as a monocaulous stem. The first branches developed when the stem attained a minimum height of 5 m. Lateral branches bore terminal cones and were determinate and deciduous. They grew to a maximum length of 1 m, and became smaller and more closely spaced with increasing stem height. The branch scars were not disrupted by secondary stem growth indicating that the branches stayed attached until the stem attained its determinate growth limit. The plant grew to a height of 25 m. Though B. punctatum is an uncommon component of Euramerican floras, the plant could become locally dominant under favorable environmental and edaphic conditions. The upper canopy was formed by B. punctatum and contained emergents of Lepidodendron aculeatum and a Sigillaria species. The understory contained pteridosperms and rare Calamites. Bothrodendron punctatum seems to have preferred environments transitional between clastic and peat swamp conditions. It was sensitive to local inhomogeneity in microhabitat characteristics, as well as to regional climatic fluctuations (drought stress). Both these variables produce specifically attributable effects on branch size and separation trends.