INSECT BORINGS PRESERVED IN WOOD FROM THE PETRIFIED FOREST MEMBER OF THE CHINLE FORMATION, WOLVERINE BENCH, GRAND STAIRCASE-ESCALANTE NATIONAL MONUMENT

An exceptionally well-preserved segment of petrified log (22.0 cm long x 17.5 cm diameter) containing previously undescribed boring traces was recovered from the Petrified Forest Member of the Chinle Formation (Upper Triassic) on the Wolverine Bench in the Grand Staircase Escalante National Monument, Utah. The ovoid to flask-shaped borings have mean dimensions of 25.5 mm long x 5.5 mm wide at the base x 2.4 mm wide at the neck. The borings resemble Gastrochaenolites and Teredolites in shape, but appear to be surface parallel borings rather than perpendicular to the log surface. These fossilized borings compare well with modern bark beetle borings, although they differ in overall morphology. Most modern bark beetle borings are produced at the bark-wood interface, and become visible only where bark has been removed. The borings on this particular segment are oriented perpendicular to the vertical axis of the log segment. The organisms that created these borings seem to have bored in a uniformly spaced, repetitive columnar pattern, visible only on the side of the specimen where the bark is missing. This suggests the insect borings were produced prior to removal of bark and transport to its site of burial and fossilization. Some of the borings preserve an unusual texture within the chambers, which may be fossilized frass. Further evaluation of this specimen and comparison with modern and fossil wood boring organisms will permit greater understanding of ancient terrestrial ecosystems.