Hard-hit groups include brachiopods, trilobites, and reef-building organisms; the reef-building organisms almost completely disappeared. Leading hypotheses include changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism.
The impact of a comet or another extraterrestrial body has also been suggested, During the Late Devonian, the continents were arranged differently, with a supercontinent, Gondwana, covering much of the Southern Hemisphere.
This includes the flowering plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses and the green algae, and excludes the red and brown algae.
Historically, plants formed one of two kingdoms covering all living things that were not animals, and both algae and fungi were treated as plants; however all current definitions of "plant" exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria).
Euramerica and Gondwana were beginning to converge into what would become Pangaea.