A microanatomical and histological study of the paired fin skeleton of the Devonian sarcopterygian Eusthenopteron foordi

Sections of fore- and hindlimbs of a Paleozoic sarcopterygian (Eusthenopteron foordi from the Devonian) possess a thin cortical compacta and an extensive and relatively loose medullary spongiosa. Most long bones have no free medullary cavity. The smallest bones appear to have a proportionately thicker cortical compacta (although the trend is not statistically significant) and a free medullary cavity. The morphological synapomorphies of panderichthyids and stegocephalians that could be interpreted as suggesting a life in shallow water and possibly occasional excursions on dry land are absent in E. foordi. Thus, recent data on sarcopterygian morphology are congruent with recent paleoecological interpretations that E. foordi lived in a marginal marine or estuarine environment and had an aquatic lifestyle.