The Palaeozoic Era was a time of major evolution and diversification of plants, as they adapted from aquatic to terrestrial habitats. The new habitats were not yet populated by animals, and were harsh and inhospitable. Nevertheless, from the earliest intertidal vegetation of the Silurian Period (425 million years ago), plants progressively became established on land, and eventually developed into the lush tropical wetland forests of the Late Carboniferous Period (300 million years ago). Towards the end of the Palaeozoic (250 million years ago), a traumatic episode beset land plants and many of the previously dominant forms became extinct. The emptying of the many ecological niches provided an opportunity for more advanced groups such as cycads and conifers to radiate into the Mesozoic Era, and marked the start of the development of a modern style of vegetation.