<P> Pangaea or Pangea (/ pænˈdʒiːə /) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras . It assembled from earlier continental units approximately 335 million years ago, and it began to break apart about 175 million years ago . In contrast to the present Earth and its distribution of continental mass, much of Pangaea was in the southern hemisphere and surrounded by a superocean, Panthalassa . Pangaea was the most recent supercontinent to have existed and the first to be reconstructed by geologists . </P> <P> The name "Pangaea / Pangea" is derived from Ancient Greek pan (πᾶν, "all, entire, whole") and Gaia (Γαῖα, "Mother Earth, land"). The concept that the continents once formed a continuous land mass was first proposed by Alfred Wegener, the originator of the scientific theory of continental drift, in his 1912 publication The Origin of Continents (Die Entstehung der Kontinente). He expanded upon his hypothesis in his 1915 book The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), in which he postulated that, before breaking up and drifting to their present locations, all the continents had formed a single supercontinent that he called the "Urkontinent". </P>

What was the landmass called when all the continents were one