Late Ordovician mass extinctionThe Late Ordovician mass extinction (LOME), sometimes referred to as the end-Ordovician mass extinction or the Ordovician–Silurian extinction, is the first of the "big five" major mass extinction events in Earth's history, occurring roughly 445 million years ago (Ma). It is often considered to be the second-largest-known extinction event, behind only the end-Permian mass extinction, in terms of the percentage of genera that became extinct.
ConodontConodonts are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (kōnos), meaning "cone", and ὀδούς (odoús), meaning "tooth"). They are primarily known from their hard, mineralised tooth-like structures called "conodont elements" that in life were present in the oral cavity and used to process food. Rare soft tissue remains suggest that they had elongate eel-like bodies with large eyes.
Late OrdovicianSubdivision of the Ordovician according to the ICS, as of 2024.Vertical axis scale: Millions of years agoEtymologyName formalityFormalUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitEpochStratigraphic unitSeriesTime span formalityFormalThe Late Ordovician is the third and final epoch of the Ordovician period, lasting 15.1 million years and spanning from around 458.2 to 443.1 million years ago.HirnantianThe Hirnantian is the final internationally recognized stage of the Ordovician Period of the Paleozoic Era. It was of short duration, lasting about 2.1 million years, from 445.2 to 443.1 Ma (million years ago). The early part of the Hirnantian was characterized by cold temperatures, major glaciation, and a severe drop in sea level.
EurypteridEurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the orderEurypterida. The earliest known eurypterids date to the Tremadocian stage of the Ordovician period, 480 million years ago. The group is likely to have appeared first during the Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoicchelicerate order.
ChitinozoanChitinozoa (singular: chitinozoan, plural: chitinozoans) are a group of flask-shaped, organic walled marine microfossils produced by an as yet unknown organism. Common from the Ordovician to Devonian periods (i.e. the mid-Paleozoic), the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe. This wide distribution, and their rapid pace of evolution, makes them valuable biostratigraphic markers.
AcritarchAcritarchs (from Greek achritos 'uncertain' and arché 'origin') are organic microfossils, known from the Archean eon of the Precambrian to the present. The classification is a catch all term used to refer to any organic microfossils that cannot be assigned to other groups. Their diversity reflects major ecological events such as the appearance of predation and the Cambrian explosion.
Cape Fold BeltThe Cape Fold Belt (CFB) is a 1,300 kilometres (810 mi) long fold-and-thrust mountain belt along the western and southern coastlines of Western Cape, South Africa. The Cape Fold Belt formed during the Permian period (300 to 250million years ago) in the late Paleozoic age, affecting the sequence of sedimentary rock layers of the siliciclastic Cape Supergroup with folding and faulted rocks, which were deposited in the Cape Basin in the southwestern corner of South Africa.
Hirnantian glaciationThe Hirnantian glaciation, also known as the Andean-Saharan glaciation, Early Paleozoic Ice Age (EPIA), the Early Paleozoic Icehouse, the Late Ordovician glaciation, or the end-Ordovician glaciation, occurred during the Paleozoic from around 460 to 420 million years ago.
TrilobiteClass of extinct, Paleozoic arthropodsTrilobites (; meaning "three-lobed entities") are extinctmarinearthropods that form the classTrilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described.
NektaspidaNektaspida (also called Naraoiida, Nektaspia and Nectaspida) is an extinct order of non-mineralisedartiopodanarthropods. They are known from the lower-Cambrian to the upper Silurian. Originally classified as trilobites, which they superficially resemble, they are now placed as close relatives as members of the Trilobitomorpha within Artiopoda. The order is divided into three major families; Emucarididae, Liwiidae, and Naraoiidae.
OrthoconeAn orthocone is the long, cone-shaped shell belonging to several species of ancient nautiloidcephalopod—the prehistoric ancestors of today's marine cephalopod mollusks, including the cuttlefishes, nautiluses, octopuses and squids. During the 18th and 19th centuries, all such shells discovered were given the "catch-all" name Orthoceras, thus creating a wastebasket taxon.*As an Amazon Associate I earn from qualifying purchases.