During the middle Carboniferous, continental glaciation began in the Southern Hemisphere, marine faunas suffered an extinction event, and land plants radiated. Glaciations certainly cause high-latitude cooling; they may also ameliorate (warm and moisten) equatorial climates. The differing responses of marine faunas and land floras to glaciation may relate to their differing responses to equatorial amelioration. Evidence for this amelioration during glacial onset comes from climatically-sensitive sediments and faunal migrations. If mid-Carboniferous glaciation ameliorated equatorial climates on land: 1, pre-glacial, seasonally adapted, equatorial plants should have migrated away from the equator into the low and middle latitudes; 2, the equatorial zone should have experienced increased origination rates following glaciation; the mid-Carboniferous radiation of land plants should have been centered on the equatorial zone. Data on floral mirgrations will establish the terrestrial paleoclimatic history of the mid- Carboniferous. Data on changes in the latitudinal diversity gradient of plants during this interval will carroborate that history. Data on the diversity and evolutionary rates (origination and extinction) of mid-Carboniferous plants, globally, within floral realms, and latitudinally, will indicate whether the mid-Carboniferous floral radiation was centered on the equatorial zone. A study of mid-Carboniferous phytogeography will allow evaluation of the link between biotic diversity, biogeographic differentiation and the pole-to-equator climatic gradient.
