Within the past two decades, the use of computerized databases for managing data from all types of fossils has become commonplace. Perhaps the major advantage for palaeontology, as for biology, is that databases allow for the management of large datasets and the easy manipulation of data. The use of large datasets in palaeontology means that new types of analyses can be performed. Palaeobiogeography, i.e., analyzing the geographical organization of biotic organisms via their fossil remains, has thus become more usable and flexible, and today large databases exist which detail the geographical and temporal extent of a variety of fossil groups.

This study draws data from a new compilation, The Orthida Database, which includes data at the generic level from a very diverse group of brachiopods, the Orthida. The orthides were especially numerous in the Early Palaeozoic when the group virtually dominated shallow water environments with other brachiopod groups such as the strophomenides. The orthides are best known from the palaeoplates of the early Palaeozoic greater Iapetus Ocean, a large ocean that stretched between Gondwana (then e.g., Africa, Antarctica), Baltica (Europe) and Laurentia (North America); a region which is of primary interest when we attempt to reconstruct the palaeoposition and movements of the continental plates of the Earth. By analyzing the distribution of the various orthides, constraints can be applied to the palaeoreconstruction of the greater Iapetus Ocean.

The orthide data were analyzed using a variety of analytical methods, including clustering (hierarchial grouping of taxonomic data) and ordination (reducing multivariate datasets to fewer variables). These two methods are relatively widely used in palaeobiogeography. Furthermore, diversity curves have been drawn for the various plates and terranes of the greater Iapetus Ocean region, and the endemic properties of the orthide faunas were examined.

The analyses show that the distributional history of the orthides of the greater Iapetus Ocean can be divided into five intervals. The first event was a rapid diversification that occurred during the Early Ordovician, when the orthides went from a handful of families scattered over a few plates to a group of high generic diversity that was found all over the Iapetus area. The second event was a significant reduction in diversity that occurred in the Middle Ordovician. The third event was a renewed diversification during the early Caradoc, which was followed by a dramatic reduction in diversity occurring during the Late Ordovician, probably as a response to a cooling global climate. Finally, as most of the plates of the region moved closer together during the Silurian, the composition of the orthide faunas became gradually more homogenous in response. In summary, the ways that the orthides were organized during the Ordovician-Silurian seems to be directly related to the ways that the plates were organized, i.e., the peri-Gondwanan terranes that were relatively closely positioned shared faunas more alike each other than with any other plate.