n. The second (510 to 439 millions years ago) of six periods that constitute the Palaeozoic Era, named after an ancient Celtic tribe, the Ordovices. The Ordovician follows the Cambrian and precedes the Silurian. It is noted for the presence of various rapidly evolving graptolite genera and of th e earliest jawless fish.
The second earliest period of the Paleozoic era (after the Cambrian and before the Silurian), thought to have covered the span of time between 490 and 443 million years ago; also, the corresponding system of rocks. It is named after a Celtic tribe called the Ordovices. In the older literature the Ordovician is sometimes know as the Lower Silurian .
The second of the six Geologic Periods of the Paleozoic Era. It extends from the end of the Cambrian Period (about 500 million years ago) to the beginning of the Silurian Period (about 435 million years ago).
the second epoch of the Palaeozioc era lasting 60 million years during which marine invertebrates flourished; named after the native British Ordovices tribe which inhabited the area in North wales where outcrops of these rocks occur.
the period of geological time between 505 and 440 million years ago. The name comes from the Ordovices, a Celtic tribe which lived in Wales in the region where these rock units were first defined. See Geological Timescale. Page up
a geological period, the second in the Paleozoic era, after the Cambrian and before the Silurian. The Ordovician is characterized by the appearance of jawless fishes and the development of many trilobites, brachiopods and other invertibrates; the rocks formed in this period. [AHDOS
The Ordovician period is the second of the six (seven in North America) periodsThe Carboniferous in North America is divided in two, the Mississippian and the Pennsylvanian. of the Paleozoic era. It follows the Cambrian period and is followed by the Silurian period. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879, to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in northern Wales into the Cambrian and Silurian periods respectively.