PREDATION REPAIR FREQUENCY IN BRACHIOPODS OF THE ORDOVICIAN CORRYVILLE MEMBER, GRANT LAKE FORMATION, KENTUCKY
Specimens from 11 stratigraphically distinct samples were identified to the genus level and examined for predatory repair scars. Generic richness and evenness were calculated for each sample, as was repair scar frequency (RF) for the complete sample as well as the genera Hebertella and Rafinesquina.
Richness ranges from 10 to 6, and evenness ranges from 0.46 to 0.86. RF of all taxa ranges from 0.02 to 0.07. RF for Hebertella ranges from 0 to 0.09. RF for Rafinesquina, which had the highest RF throughout all the samples, ranges between 0.07 and 1. Rafinesquina RF has a mean of 0.33 with a median value of 0.25. RF data for both taxa show some similar peaks through time, but it should be noted that two samples had only two and five Rafinesquina specimens, so the RF of 1.0 and 0.60 (respectively) may be a result of small sample size. There was no statistically significant correlation between richness or evenness and any of the three RF trends through time.
Rafinesquina‘s high RF may be due to its flat shape or to some sort of other predator preference, such as taste. More globose brachiopods may have been less likely to survive predatory attacks, or their shells may have been more likely to fall apart during taphonomic processes. Additionally, Rafinesquina have fine shell ornamentation, whereas other brachiopods have much deeper grooves that can trap large amounts of sediment, fusing to the fossil and hiding repair scars.