PALEOBIOGEOGRAPHY OF THE PALEOZOIC STROMATOPOROIDEA

[Specific authorships of Ordovician, Silurian, and Devonian biogeography are indicated within] some exceptions to this generalization have been observed. On continental portions of tectonic plates, as eustatic sea level rose, epeiric seas formed in low-lying areas, providing new, more extended regions for stromatoporoid habitation. Increases in eustatic sea level result from the melting of glacial ice as a byproduct of global warming, and/or from an increase in the rate of seafloor spreading, which raises the level of the seafloor, causing seawater to spill onto low-lying parts of continents (e.g., lieBermaN, 2000, p. 86). There is no uniform agreement among biogeographers where it comes to the delin-eation of synchronous areas containing different assemblages of taxa, known as biogeographic units (CeCCa, 2002, p. 81). Among paleontologists, kauffmaN (1973), working with Cretaceous bivalves, deter-mined that a realm is a biogeographic unit containing more than 75 % endemic taxa (i.e., at least 75 % of the genera present are found in no other realm), an approach accepted in theory by BouCot (1975) for Paleozoic brachiopods. oliver (1977) found percentages of endemism for rugose coral genera in the Early and Middle Devonian ranged from 33 % in the Siege-nian (Pragian) to 92 % in the late Emsian. Similar data are presented here, because it is at the level of genus that the group is most clearly defined and characterized, thank