DevonianSubdivision of the Devonian according to the ICS, as of 2024Vertical axis scale: Millions of years agoEtymologyName formalityFormalNickname(s)Age of FishesUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitPeriodStratigraphic unitSystemTime span formalityFormalLower boundary definitionFAD of the GraptoliteLower boundary GSSPKlonk, Czech Republic49°51′18″N13°47′31″E / 49.8550°N 13.7920°E / 49.8550; 13.7920Lower GSSP ratified1972Upper boundary definitionFAD of the ConodontSiphonodella sulcata (discovered to have biostratigraphic issues as of 2006).Upper boundary GSSPLa Serre, Montagne Noire, France43°33′20″N3°21′26″E / 43.5555°N 3.3573°E / 43.5555; 3.3573Upper GSSP ratified1990Atmospheric and climatic dataSea level above present dayRelatively steady around 189 m, gradually falling to 120 m through periodThe Devonian ( ) is a geologic period and system of the Paleozoicera during the Phanerozoiceon, spanning 60.7 million years from the end of the preceding Silurian period at 419.62 million years ago (Ma), to the beginning of the succeeding Carboniferous period at 358.86 Ma.
SilurianSubdivision of the Silurian according to the ICS, as of 2024.Vertical axis scale: Millions of years agoEtymologyName formalityFormalSynonym(s)GotlandianUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitPeriodStratigraphic unitSystemFirst proposed byRoderick Murchison, 1835Time span formalityFormalLower boundary definitionFAD of the GraptoliteLower boundary GSSPDob's Linn, Moffat, United Kingdom55°26′24″N3°16′12″W / 55.4400°N 3.2700°W / 55.4400; -3.2700Lower GSSP ratified1984Upper boundary definitionFAD of the Graptolite Monograptus uniformisUpper boundary GSSPKlonk, Czech Republic49°51′18″N13°47′31″E / 49.8550°N 13.7920°E / 49.8550; 13.7920Upper GSSP ratified1972Atmospheric and climatic dataSea level above present dayAround 180 m, with short-term negative excursionsThe Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at 443.1 Ma (million years ago) to the beginning of the Devonian Period, 419.62 Ma.
FossilPreserved remains or traces of organisms from a past geological ageExamples of animal fossils. Clockwise from top left: Onychocrinus, Palaeosinopa, Gryphaea, and HarpactocarcinusA fossil (from Classical Latinfossilis, lit. 'obtained by digging') is any preserved remains, impression, or trace of any once-living thing from a past geological age.
VertebrateSubphylum of chordatesVertebrates (), also called craniates, are animals with a vertebral column and a cranium. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylumVertebrata ( ) with some 65,000 species, by far the largest ranked grouping in the phylumChordata. The vertebrates include mammals, birds, amphibians, and various classes of fishes and reptiles.
AnimalBiological kingdomAnimals are multicellular, eukaryoticorganisms belonging to the biologicalkingdomAnimalia (). Animals consume organic material, breathe oxygen, have muscle cells, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. With few exceptions, animals are able to move. Animals form a clade, meaning that they arose from a single common ancestor.
HeadA head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aids in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may not have a head, but many bilaterally symmetric forms do, regardless of size. Heads develop in animals by an evolutionary trend known as cephalization.
Ancient GreekAncient Greek (Ἑλληνική, Hellēnikḗ [hellɛːnikɛ̌ː]) includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (c. 1400 – c. 1200 BC), Dark Ages (c. 1200 – c. 800 BC), the Archaic or Homeric period (c. 800 – c. 500 BC), and the Classical period (c. 500 – c. 300 BC).
PaleozoicEtymologyName formalityFormalAlternate spelling(s)PalaeozoicUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitEraStratigraphic unitErathemLower boundary definitionAppearance of the IchnofossilTreptichnus pedumLower boundary GSSPFortune Head section, Newfoundland, Canada47°04′34″N55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310Lower GSSP ratifiedAugust 1992 (as base of Cambrian)Upper boundary definitionFirst appearance of the Conodont Hindeodus parvus.Upper boundary GSSPMeishan, Zhejiang, China31°04′47″N119°42′21″E / 31.0798°N 119.7058°E / 31.0798; 119.7058Upper GSSP ratifiedMarch 2001The Paleozoic ( , , ; or Palaeozoic) Era is the first of three geological eras of the Phanerozoic Eon.
EndoskeletonAn endoskeleton (from Ancient Greek ἔνδον (éndon), meaning "inside", and σκελετός (skeletós), meaning "skeleton") is a structural frame (skeleton) — usually composed of mineralized tissue — on the inside of an animal, overlaid by soft tissues. Endoskeletons serve as structural support against gravity and mechanical loads, and provide anchoring attachment sites for skeletal muscles to transmit force and allow movements and locomotion.
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.
ThoraxThe thorax (pl.: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the body, each in turn composed of multiple segments. The human thorax includes the thoracic cavity and the thoracic wall.
Plate (anatomy)A plate in animal anatomy may refer to several things: Flat bones (examples: bony plates, dermal plates) of vertebratesan appendage of the Stegosauria group of dinosaursarticulated armoured plates covering the head of thorax of Placodermi (literally "plate-skinned"), an extinct class of prehistoric fish (including skull, thoracic and tooth plates)bony shields of the Ostracoderms (armored jawless fishes) such as the dermal head armour of members of the class Pteraspidomorphi that include dorsal, ventral, rostral and pineal platesplates of a carapace, such as the dermal plates of the shell of a turtledermal plates partly or completely covering the body of the fish in the order Gasterosteiformes that includes the sticklebacks and relativesplates of dermal bones of the armadilloZygomatic plate, a bony plate derived from the flattened front part of the zygomatic arch (cheekbone) in rodent anatomyOther flat structureshairy plate-like keratin scales of the pangolinBasal plate (other), several anatomy-related meaningsOther meanings in human anatomyAlar plate, a neural structure in the embryonic nervous systemCribriform plate, of the ethmoid bone (horizontal lamina) received into the ethmoidal notch of the frontal bone and roofs in the nasal cavitiesEpiphyseal plate, a hyaline cartilage plate in the metaphysis at each end of a long boneLateral pterygoid plate of the sphenoid, a broad, thin and everted bone that forms the lateral part of a horseshoe like process that extends from the inferior aspect of the sphenoid boneNail plate, the hard and translucent portion of the nailPerpendicular plate of the ethmoid bone (vertical plate), a thin, flattened lamina, polygonal in form, which descends from the under surface of the cribriform plate, and assists in forming the septum of the noseRelated structuresScute, a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians and the feet of birdsSclerite, a plate forming the exoskeleton of invertebratesSee alsoPlate (other) This includes a list of related items that share the same name (or similar names).Lists of prehistoric fishPrehistoric fish are early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Quaternary. The study of prehistoric fish is called paleoichthyology. A few living forms, such as the coelacanth are also referred to as prehistoric fish, or even living fossils, due to their current rarity and similarity to extinct forms.
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