The Upper Ordovician Winterhouse Formation of Western Newfoundland contains a, hitherto undescribed, well-preserved and diverse assemblage of trace fossils. This study provides the first systematic ichnological review of the area. 20 ichnotaxa are documented herein from the mudstone and sandstone storm deposits of the formation. A detailed morphologic three-dimensional reconstruction and analysis of a complex Parahaentzschelinia-like burrow system that is prolific throughout the formation is also undertaken. This analysis allows for a reconsideration of the trace-maker’s ethology and paleobiology, and highlights a need for a systematic ichnotaxonomic review of Parahaentzschelinia. Additional reconstructions of natural mineral-filled fractures associated with Parahaentzschelinia-like burrows in the cemented silt-rich fine-grained sandstones illustrate that the burrows create planes of weakness within the cemented sandstone, along which natural fractures preferentially propagate. This suggests that these trace fossils create mechanical heterogeneities that can steer fracture development, and can potentially have a dramatic effect on reservoir charactertstics in bioturbated reservoirs where induced fracturing techniques may be employed
