Geographic bias in the fossil record: tests using Chinese early Paleozoic echinoderms

Abstract The greater diversity of fossils known from North America and Europe, plus the correlation between outcrop area and paleobiodiversity, introduce a potential bias in the fossil record. We develop tests to detect actual bias using recent discoveries of Chinese early Paleozoic fossil echinoderms and the idea that geographic bias can exist only if poorly known parts of the globe contain novel fossils yet unknown to science. Fossil echinoderms had complex skeletons requiring rapid burial, so proportionately more novel forms may be undiscovered. Echinoderm diversity was high in the early Paleozoic, and this time interval includes several Chinese fossil Lagerstätten that enhance the chances of discovering novelties. Chinese fossil echinoderms are categorized as “genuine novelties” or “more of the same.” We use taxonomic, phylogenetic, and morphological approaches because some novel echinoderms are undescribed and cannot be used in a taxonomic assessment alone. Results suggest that the known Chinese early Paleozoic echinoderm fauna is predominantly more of the same. Nevertheless, historic discovery curves show that knowledge of Chinese fossil echinoderms is increasing rapidly, so they are still poorly known. If significantly novel echinoderms are rare, as recent discoveries elsewhere suggest, then Chinese fossil echinoderms need further exploration to discover the rarities. Our preliminary results need confirmation. A potential explanation of our results is that modern continents include sedimentary rocks deposited in different provinces during the early Paleozoic, so each may well provide an adequate sample on which to build global diversity curves.