A chordate is a deuterostomic animal belonging to the phylum Chordata. All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa. These five synapomorphies are a notochord, a hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anal tail. The name "chordate" comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate body plan structuring and movements. Chordates are also bilaterally symmetric, have a coelom, possess a closed circulatory system, and exhibit metameric segmentation.
The Cambrian Period is the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, and its base, are somewhat in flux.
The PaleozoicEra is the first of three geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic and ends 251.9 Ma at the start of the Mesozoic Era. The Paleozoic is subdivided into six geologic periods :
The Precambrian is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.
The Furongian is the fourth and final epoch and series of the Cambrian. It lasted from 497 to 485.4 million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian Stage. It is subdivided into three stages: the Paibian, Jiangshanian and the unnamed 10th stage of the Cambrian.
Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the east shore of J.P. Koch Fjord in the far north of Greenland. It was discovered in 1984 by A. Higgins of the Geological Survey of Greenland. A preliminary account was published by Simon Conway Morris and others in 1987 and expeditions led by J. S. Peel and Conway Morris have returned to the site several times between 1989 and the present. A field collection of perhaps 10,000 fossil specimens has been amassed. It is a part of the Buen Formation.
The Paibian is the lowest stage of Furongian series of the Cambrian. It follows the Guzhangian and is succeeded by the Jiangshanian Stage. The base is defined as the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago. The top, or the base of the Jiangshanian is defined as the first appearance of the trilobite Agnostotes orientalis around 494 million years ago.
The Van Railway was a standard gauge railway in mid Wales. The line was built in 1871 to link the highly productive lead mines at Van, near Llanidloes to the main Cambrian line at Caersws. The mines closed in 1920, but the railway remained open until 1940.
The Cambrian explosion, Cambrian radiation,Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately 538.8 million years ago in the Cambrian Period of early Paleozoic when there was a sudden radiation of complex life and practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.
Lôn Cambria is the section in Wales of National Cycle Route 81 in the British National Cycle Network, which runs from Aberystwyth to Wolverhampton.
The Terreneuvian is the lowermost and oldest series of the Cambrian geological system. Its base is defined by the first appearance datum of the trace fossil Treptichnus pedum around 538.8 million years ago. Its top is defined as the first appearance of trilobites in the stratigraphic record around 521 million years ago. This series' name was formally accepted by the International Commission on Stratigraphy in 2007.
Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian Series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia. Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy. The preferred definitions for the lower boundary are the first appearance of the molluscs Watsonella crosbyi or Aldanella attleborensis around 529 million years ago. The correlation between the lowest occurrences of A. attleborensis and W. crosbyi with the Zhujiaqing positive carbon isotope excursion (ZHUCE) has led to the conclusion that the combination of these two markers are a reliable indicator of the boundary between the Fortunian and Stage 2. The proposed upper boundary might be the first appearance of trilobites around 521 million years ago.
The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite Lejopyge laevigata around 500.5 million years ago. The Guzhangian-Paibian boundary is marked by the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago.
The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about 509 to 497 million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is preceded by the unnamed Cambrian Series 2 and succeeded by the Furongian series.
Westergaardodina is a species-rich genus of spine, U or W-shaped paraconodont known from Middle Cambrian to Lower Ordovician strata.
The Mount Simon Sandstone is the basal sandstone of the Potsdam Sandstone. It was deposited in a nearshore environment, unconformably overlying Precambrian basement.
Gapparodus is an extinct genus of conodonts in the family Furnishinidae. Gapparodus gapparites is a species of the Early Cambrian of Shuijingtuo Formation in China.
Eoconodontus is an extinct genus of conodonts of the Late Cambrian. It is a two-elements genus from the Proconodontus lineage.
Protohertzina is a genus of conodonts or, possibly, Chaetognaths, found at the beginning of the Cambrian explosion.
Kutorginates (Kutorginata) are an extinct class of early rhynchonelliform ("articulate") brachiopods. The class contains only a single order, Kutorginida (kutorginides). Kutorginides were among the earliest rhynchonelliforms, restricted to the lower-middle part of the Cambrian Period.
