EIGENSHAPE ANALYSIS AS A TOOL FOR FAMILY-LEVEL IDENTIFICATION OF NEPOMORPHANS FROM THE SOLITE LAGERSTATTE (TRIASSIC, VIRGINIA)

The Solite Quarry, located in the Triassic Danville-Dan River Basin, is a Lagerstätte comprised of microlaminated shales that preserve an exceptional record of late Triassic insect diversity. Present in rocks from the 3 cm-thick “insect layer” are two-dimensional carbonized remains of members of an unidentified nepomorphan family. Because of the nature of their two-dimensional preservation, we are limited in the methods we can use for their analysis. This is further complicated by the fact that much of the thorax is obscured by the legs in most specimens.

The goal of our research is to utilize eigenshape analysis on high-resolution photos of these insects to determine which modern nepomorphan family they are most similar to in shape. To accomplish this, we used TpsDig2 to collect 100 equally-spaced x, y coordinates around the six proximal leg elements of 172 unidentified Solite nepomorphans from the Virginia Museum of Natural History collection. We selected specimens that were preserved in the same orientation and with the same level of taphonomic detail. We then outlined the analogous parts of approximately 40 specimens each from four different modern nepomorphan families: Notonectidae, Corixidae, Belostomatidae, and Naucoridae. Each outline was subjected to a standard eigenshape analysis, standardizing for body size, rotation, and translation. Results from the modern families were compared to the fossil material to determine the degree of morphological similarity. Preliminary results suggest the preserved part of the insects in question is most similar in morphology to Notonectidae. Understanding the relationship these insects have to modern nepomorphans will help us to better understand the significance of Solite with regard to the evolutionary development of “true bugs,” particularly in the wake of the Permo-Triassic mass extinction.