MEASURING BODY SIZE FROM GENUS-LEVEL COMPENDIA CAPTURES SIZE EVOLUTION TRENDS IN COMPONENT SPECIES: VALIDATION USING FORAMINIFERA, OSTRACODA, AND CONODONTA

Body size evolution occurs within populations, but macroevolutionary studies of size evolution often (out of necessity) use one or a few specimens to represent the sizes of populations, species, or even genera. Because synoptic paleobiological compendia are typically focused at the genus level, using selected specimens and species to represent the size of a genus is a convenient approach to capturing size trends across many thousands of genera. However, the extent to which genus-level body size patterns reflect trends at the species level across time and taxa remains poorly known. To determine the extent of correspondence between genus- and species-level body size data, we measured illustrated specimens from both genus- and species-level compendia of foraminiferans, ostracods, and conodonts. Our dataset includes over 500 genera of foraminiferans and ostracods and 60 conodont genera representing a total of 49,662 species. We find that specimen sizes from genus-level compendia correlate strongly with minimum, mean, and maximum size across species for all three clades. There is also significant correlation between temporal trends in body size estimated using genus- and species-level data. The results from these three ecologically disparate and distantly related clades, spanning protists, protostomes, and deuterostomes, suggest that body size estimates from genus-level compendia are sufficient to capture first-order trends in the evolution of organism size over geologic time.