How good is the fossil record of arthropods? An assessment using the stratigraphic congruence of cladograms

A total of 179 published cladograms of arthropods was tested for their cong ruence with the palaeontological record. Congruence for data sets including 510 tetrapod and 157 fish trees was also calculated for comparison. Result s provide support for the hypothesis that the fossil record of arthropods i s less complete (at levels of stratigraphic and taxonomic resolution pertin ent to most macroevolutionary studies) than the records of several other ta xa. Differences in tree size, shape, balance and the distribution of first stratigraphic appearances (potential sources of bias) were controlled for b y various randomization procedures. Most measures of congruence for arthrop ods were statistically poorer than those for other groups, even when the sa mple was divided into broad temporal bins. Many of the most robust and wide ly reproduced sister groupings of arthropods are attended by ghost ranges o f many tens or hundreds of millions of years. Fossils of a number of presen tly very diverse and abundant arthropod groups are conspicuously absent fro m the record, despite many spectacular examples of the detailed preservatio n of others. There is probably no single reason for the apparently poor rec ord of arthropods. Low preservation potential, small size of individuals, s mall numbers of individuals, and restricted palaeobiogeography almost certa inly play a role in particular cases. Copyright (C) 2001 John Wiley & Sons, Ltd.