Wallace Line by the Sahul Shelf to New Guinea. The biogeographic boundary known as Lydekker's Line, which separates the eastern edge of Wallacea from the Australian region, has a similar origin to the Wallace line. During ice age glacial advances, when the , both Asia and Australia were united with what are now islands on their respective continental shelves as continuous land masses, but the deep water between those two large continental shelf areas was, for over 50 million years, a barrier that kept the flora and fauna of Australia separated from those of Asia. Wallacea consists of islands that were not
Uerdingen line Uerdingen line The Uerdingen Line (named after Uerdingen by Georg Wenker) is the isogloss within West Germanic languages that separates dialects which preserve the -"k" sound in the first person singular pronoun word "ik" (north of the line) from dialects in which the word final -"k" has changed to word final -"ch" in the word "ich" (IPA ) (south of the line). This sound shift is the one that progressed the farthest north among the consonant shifts that characterize High German and Middle German dialects. The line passes through Belgium, the Netherlands, and Germany. North of the line Low German