Tetragraptus approximatusTetragraptus approximatus is a species of dichograptidgraptolite belonging to the genusTetragraptus. It existed during the FloianAge (477.1 million years ago) of the Ordovician. It is an important index fossil in biostratigraphy. DescriptionThe general outline of each Tetragraptus approximatus colony (rhabdosome) is highly distinctive.DapingianThe Dapingian is the third stage of the Ordovician system and the first stage of the Middle Ordovician series. It is preceded by the Floian and succeeded by the Darriwilian. The base of the Dapingian (and the top of the Floian) is defined as the first appearance of the conodont species Baltoniodus triangularis which happened about 471.3 million years ago. The Dapingian lasted for about 1.9 million years until about 469.4 million years ago.
TremadocianThe Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from 486.85 to 477.1 million years ago. The base of the Tremadocian is defined as the first appearance of the conodont species Iapetognathus fluctivagus at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland.
Early OrdovicianSubdivision of the Ordovician according to the ICS, as of 2024.Vertical axis scale: Millions of years agoEtymologyChronostratigraphic nameLower OrdovicianGeochronological nameEarly OrdovicianName formalityFormalUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitEpochStratigraphic unitSeriesTime span formalityFormalLower boundary definitionFAD of the conodontIapetognathus fluctivagus.Lower boundary GSSPGreenpoint section, Green Point, Newfoundland, Canada49°40′58″N57°57′55″W / 49.6829°N 57.9653°W / 49.6829; -57.9653Lower GSSP ratified2000Upper boundary definitionFAD of the conodontBaltoniodus triangularisUpper boundary GSSPHuanghuachang section, Huanghuachang, Yichang, China30°51′38″N110°22′26″E / 30.8605°N 110.3740°E / 30.8605; 110.3740Upper GSSP ratified2007Atmospheric and climatic dataMean atmospheric O2 contentc.
OrdovicianThe Ordovician ( or-də-VISH-ee-ən, -doh-, -VISH-ən) 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 43.75 million years from the end of the Cambrian Period 486.85 Ma (million years ago) to the start of the Silurian Period 443.1 Ma.
First appearance datumFirst appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest fossil discovered, to date, of a particular species. A related term is last appearance datum (LAD), the last appearance of a species in the geologic record. FADs are frequently used to designate segments in the geologic time scale.
SwedenCountry in northern EuropeSweden, formally the Kingdom of Sweden, is a Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east, and shares a maritime border with Denmark to the south. At 450,295 square kilometres (173,860 sq mi) and with a population of 10.6 million, Sweden is the largest and most populous Nordic country, and is the fifth-largest country in Europe.
GraptoliteGraptolites are a group of colonial animals, members of the subclass Graptolithina within the classPterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the Lower Carboniferous (Mississippian). A possible early graptolite, Chaunograptus, is known from the Middle Cambrian.
ConodontConodonts are an extinct group of marine jawless vertebrates belonging to the classConodonta (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.
ChinaCountry in East AsiaChina, officially the People's Republic of China (PRC), is a country in East Asia. It is divided into 33 province-level divisions, including two special administrative regions. Beijing is the capital, while Shanghai is the most populous city by urban area. Its geography features the Central Plain, major rivers such as the Yangtze and Yellow River, deserts, subtropical and temperate forests, plateaus, and mountain ranges such as the Himalayas.
Geologic time scaleThe geologic time scale or geological time scale describes how geologic time is divided into standardised intervals. It uses the rock record together with the principles of chronostratigraphy to place rock sequences into their relative age positions, and geochronology techniques, such as radiometric dating, to precisely date the boundaries between them.*As an Amazon Associate I earn from qualifying purchases.