Earth was in an ice age with a climate much like today-ice on both poles with wet tropics near the equator and temperate regions between. Significant glaciation marks the beginning of the Pennsylvanian with a resultant sea-level drop. This advance enabled the eventual conquest of land by reptiles, mammals, and birds. A crucial development of this Period was the evolution of the land adapted, membrane enclosed (amniote) egg, allowing animals to live away from water. These animals ate insects, other arthropods, and each other. This Period is known as the Age of Amphibians due to their numbers and variety. Insects and other arthropods were the main herbivores (vertebrates had not yet evolved the complex digestive strategies needed to eat plants). Pennsylvanian forests and swamps were home to a rich diversity of animals, particularly winged insects. This allowed the evolution of giant invertebrates, for example, dragonflies with 70 cm (29 in) wingspans and two-meter long millipedes. The vast amont of carbon deposited as coal, rather than carbonate (CO 3 2-), released oxygen into the atmosphere, increasing atmospheric oxygen to 35% (vs. Late Pennsylvanian temperate forests were dominated by cordaites. Specimens of all but cordaites are displayed in this case. Dominant plants included giant club mosses and horsetails, tree ferns, seed ferns and cordaites (conifer-like trees). These rich deposits make these forest plants some of the best known in Earth’s history. Tropical forests of this Period provided the plant matter that later became the great coal deposits of America and Europe. The dead plant material was laid down in huge amounts, gradually forming today's coal. On land coal swamp forests thrived during this period. The warm, clear seas of the Mississippian gave way to cool, muddy waters resulting in a decline in crinoids from which they never recovered. The Pennsylvanian* saw the disappearance of the warm, shallow seas of the Mississippian, causing a dramatic change in marine life.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |