The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 Ma to the start of the Silurian Period 443.8 Ma.
John William Salter was an English naturalist, geologist, and palaeontologist.
Han is a monotypic genus of agnostid trilobite, whose sole member is Han solo. The type specimen of H. solo was found in marine strata of the Arenig to Llanvirn-aged Zitai Formation of Middle Ordovician southern China and is named after the character in Star Wars.
In geology, the Llandeilo Group is the middle subdivision of the British Ordovician rocks. It was first described and named by Sir Roderick Murchison from the neighborhood of Llandeilo in Carmarthenshire. In the type area it consists of a series of slaty rocks, shales, calcareous flagstones and sandstones; the calcareous middle portion is sometimes termed the Llandeilo limestone; and in the upper portion volcanic rocks are intercalated.
In the geologic timescale, the Rhuddanian is the first age of the Silurian Period and of the Llandovery Epoch. The Silurian is in the Paleozoic Era of the Phanerozoic Eon. The Rhuddanian Age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma. It succeeds the Hirnantian Age and precedes the Aeronian Age.
Agnostus is a genus of agnostid trilobites, belonging to the family Agnostidae, that lived during the late Middle Cambrian – early Upper Cambrian. It is the type genus of the family Agnostidae and is subdivided into two subgenera, Agnostus and Homagnostus.
Flexicalymene Shirley, 1936. is a genus of trilobites belonging to the order Phacopida, suborder Calymenina and Family Calymenidae. Flexicalymene specimens can be mistaken for Calymene, Gravicalymene, Diacalymene and a few other Calymenina genera. They are used as an index fossil in the Ordovician. Ohio and North America are particularly known for being rich with Flexicalymene fossils.
Gravicalymene Shirley, 1936, is a genus of trilobites belonging to the order Phacopida, suborder Calymenina and family Calymenidae. Species included in this genus have previously been allocated to Calymene Brongniart 1822,Flexicalymene Shirley, 1936. and Sthenarocalymene Siveter 1977.
In geology, the Arenig is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval.
The Kirengellids are a group of problematic Cambrian fossil shells of marine organisms. The shells bear a number of paired muscle scars on the inner surface of the valve.
Sphaeragnostus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It can be recognized by having two thorax segments, a totally effaced headshield, while the tailshield although effaced, has a clear furrow parallel to its border, and a short, convex, subcircular axis. It lived during the Ordovician.
Geragnostus is a genus of very small agnostid trilobites whose fossils are found Ordovician-aged marine strata from Eurasia, North America and Argentina.
Emmrichops is a genus of average size trilobite, assigned to the Cyclopygidae family, that lived during the Middle Ordovician (Llanvirn), and have been found in what are today the Czech Republic and in Wales. Like other cyclopygids, it has huge eyes, that occupy almost the entire free cheeks, six thorax segments and a wide tail shield. Like the other cyclopygids, Emmrichops probably lived hunting plankton in the water column. Only one species, E. planicephala, has been described sofar.
Sagavia is a genus of trilobites that lived during the Middle and Upper Ordovician in what are now Northwest and Southeast China, North Kazakhstan and Wales. It is a typical cyclopygid that can be distinguished by its large but separate eyes, elongated glabella, five thorax segments and a pygidium with clearly defined axis and border.
Placoparia is a genus of trilobites of average size that lived during the late Lower to the early Upper Ordovician on the paleocontinents Gondwana, Avalonia and Laurentia, now the Czech Republic, France, Germany, Morocco, Portugal, Spain and Wales. Its headshield is semi-circular to rectangular with rounded frontal corners. It lacks eyes, but eye ridges are present. The fact that the facial sutures are opisthoparian is an exception in the otherwise proparian Cheirurina. The thorax has 11 or 12 segments, with the axis slightly wider than the ribs to its sides. The tips of the pleurae are free, which resembles an old-fashion central heating radiator. The axis in the small tailshield consists of four rings and a minute endpiece. The four pleurae end in spatulate spines that fit to corresponding indentations in the cephalon.
There are four Llanfawr Quarries dolerite quarries near Llandrindod Wells, Wales they were excavated for building stone in the 19th and early 20th centuries. Three of these quarries constitute a Site of Special Scientific Interest and permission to collect must be sought from the Countryside Council for Wales.
Siphonotretida is an extinct order of linguliform brachiopods in the class Lingulata. The order is equivalent to the sole superfamily Siphonotretoidea, itself containing the sole family Siphonotretidae. Siphonotretoids were originally named as a superfamily of Acrotretida, before being raised to their own order.
The Pircancha Formation is a Floian to Dapingian geologic formation of southern Bolivia. The green mudstones, shales and sandstones were deposited in a shallow to open marine environment. The fossil Pircanchaspis rinconensis is named after the formation.
The Nod Glas Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is made up of pyritous, graptolitic mudstone that is generally black in colour. It weathers to a soft, very well cleaved and coal-like material. The formation runs from Conwy in the north, down to Cardigan Bay in the area around Aberdyfi and Tywyn, though it is not a continuous over this area.
The Saint-Chinian Formation is a geological formation composed of shales with limestone inclusions, dating from the Lower Ordovician (Tremadocian).
