Previous studies of overall arthropod disparity have compared Cambrian and Recent biotas, without considering taxa of intermediate age. This study explored morphological diversity among Carboniferous arthropods, primarily from the well-known Westphalian Mazon Creek Lagerstätte. Over 100 arthropod species, belonging to 48 orders, were examined. The data set is composed of nearly equal numbers of crustacean, arachnid, and insect species, with lower numbers of merostomes. Trilobites have not been found at Mazon Creek. However, some Late Carboniferous trilobite species were included in order to obtain a more representative picture of global Carboniferous arthropod disparity.
The absence, presence, or state of 66 shared characters was recorded for each species, as well as individual autapomorphies. Overall disparity was determined from the Euclidean distance analysis between taxa or variance along principal coordinates analyses (PCO) axes. Results indicate that arthropod disparity has not been greatly reduced throughout the Phanerozoic as was previously suggested. However, the regions of occupied morphospace have rotated over time.