Nevertheless, the era featured the dramatic rifting of the supercontinent Pangaea. During break-up of the supercontinent, rifting environments dominate. The vertebrate herpesviruses initially evolved ~ and underwent subsequent evolution on the supercontinent Pangaea. Geologically, the Paleozoic started shortly after the breakup of the supercontinent Pannotia. Most tropical rainforests today are on fragments of the Mesozoic era supercontinent of Gondwana. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons. The cratons (possibly) later assembled into another supercontinent called Pannotia, in the Ediacaran. Their fluctuations correlate with Precambrian supercontinent cycles. The southern continents remained tied together in the supercontinent of Gondwana. The assembly of a supercontinent would have to show intercratonic orogenic belts. The clade originated on the northern supercontinent of Laurasia. Antarctica was once part of the Gondwana supercontinent. Madagascar originated as part of the Gondwana supercontinent. Laurentia, Baltica and Siberia remained independent continents following the break-up of the supercontinent of Pannotia. The Notes column provides the geologic time period of the fully formed supercontinent.