TriassicSubdivision of the Triassic 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 unitPeriodStratigraphic unitSystemTime span formalityFormalLower boundary definitionFirst appearance of the conodontHindeodus parvusLower boundary GSSPMeishan, Zhejiang, China31°04′47″N119°42′21″E / 31.0798°N 119.7058°E / 31.0798; 119.7058Lower GSSP ratified2001Upper boundary definitionFirst appearance of the ammonitePsiloceras spelae tirolicumUpper boundary GSSPKuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria47°29′02″N11°31′50″E / 47.4839°N 11.5306°E / 47.4839; 11.5306Upper GSSP ratified2010The Triassic ( ) is a geologic period and a stratigraphic system that spans 50.5 million years from the end of the Permian Period 251.902 Ma (million years ago) to the beginning of the Jurassic Period 201.4 Ma.
EvolutionEvolution is the change in the heritable characteristics of biological populations over successive generations. It happens when individuals in a population vary in their genetic characteristics and in the numbers of their surviving offspring. Mutation introduces new genetic variation, and processes such as genetic drift, gene flow, and natural selection result in some genetic variants becoming more or less common over time.
MarsupialInfraclass of mammals in the clade MetatheriaMarsupials are a diverse group of mammals belonging to the infraclassMarsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a relatively undeveloped state and then nurtured within a pouch on their mother's abdomen.
SynapsidaClade of tetrapodsSynapsida is a diverse group of tetrapodvertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant reptiles and birds). Synapsids have a single lower temporal fenestra, an opening low in the skull roof behind each eye socket.
MammalClass of animals with milk-producing glandsA mammal (from Latin mamma 'breast') is a vertebrate animal of the classMammalia (). Mammals are characterized by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors diverged in the Carboniferous period over 300 million years ago.
JurassicThe Jurassic ( juurr-ASS-ik) is a geologic period and stratigraphic system that lasted about 58.3 million years, spanning from the end of the Triassic Period 201.4 Ma (million years ago) to the beginning of the Cretaceous Period, 143.1 Ma. The Jurassic constitutes the second and middle period of the Mesozoic Era as well as the eighth period of the Phanerozoic Eon and is named after the Jura Mountains, where limestone strata from the period were first identified.
CarboniferousFifth period of the Paleozoic EraSubdivision of the Carboniferous according to the ICS, as of 2024.Vertical axis scale: Millions of years agoEtymologyName formalityFormalNickname(s)Age of Amphibians or ReptilesUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitPeriodStratigraphic unitSystemFirst proposed byWilliam Daniel Conybeare and William Phillips, 1822Time span formalityFormalLower boundary definitionFAD of the ConodontSiphonodella sulcata (discovered to have biostratigraphic issues as of 2006)Lower boundary GSSPLa Serre, Montagne Noire, France43°33′20″N3°21′26″E / 43.5555°N 3.3573°E / 43.5555; 3.3573Lower GSSP ratified1990Upper boundary definitionFAD of the ConodontStreptognathodus isolatus within the morphotypeStreptognathodus wabaunsensis chronoclineUpper boundary GSSPAidaralash, Ural Mountains, Kazakhstan50°14′45″N57°53′29″E / 50.2458°N 57.8914°E / 50.2458; 57.8914Upper GSSP ratified1996Atmospheric and climatic dataSea level above present dayFalling from 120 m to present-day level throughout the Mississippian, then rising steadily to about 80 m at end of periodThe Carboniferous ( ) is a geologic period and system of the Paleozoicera that spans 60 million years, from the end of the Devonian Period 358.86 Ma (million years ago) to the beginning of the Permian Period, 298.9 Ma.
Ambondro mahaboAmbondro mahabo is a mammal from the Middle Jurassic (Bathonian) Isalo III Formation (about 167 million years ago) of Madagascar. The only described species of the genus Ambondro, it is known from a fragmentary lower jaw with three teeth, interpreted as the last premolar and the first two molars. The premolar consists of a central cusp with one or two smaller cusps and a cingulum (shelf) on the inner, or lingual, side of the tooth.
Pennsylvanian (geology)Subdivision of the Carboniferous 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 unitSubperiodTime span formalityFormalLower boundary definitionFirst appearance of the ConodontDeclinognathodus nodiliferus.Lower boundary GSSPArrow Canyon, Nevada, United States36°44′00″N114°46′40″W / 36.7333°N 114.7778°W / 36.7333; -114.7778Lower GSSP ratified1996Upper boundary definitionFirst appearance of the ConodontStreptognathodus isolatus within the morphotypeStreptognathodus wabaunsensis chronocline.Upper boundary GSSPAidaralash, Ural Mountains, Kazakhstan50°14′45″N57°53′29″E / 50.2458°N 57.8914°E / 50.2458; 57.8914Upper GSSP ratified1996The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the ICSgeologic timescale, the younger of two subperiods of the Carboniferous Period (or the upper of two subsystems of the Carboniferous System).
MonotremeMonotremes () are mammals of the order Monotremata. They are the only mammals still in existence which lay eggs, rather than bearing live young. The five extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tracts, reproductive tracts, and other body parts, compared to the more common mammalian types.
DryolestesDryolestes is an extinct genus of Late Jurassic mammal from the Morrison Formation and the Alcobaça Formation of Portugal. The type species Dryolestes priscus is present in stratigraphic zones 2, 5, and 6.
PlacentaliaPlacentalia () is one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished from monotremes and marsupials in that the fetus is carried in the uterus of its mother to a relatively late stage of development.*As an Amazon Associate I earn from qualifying purchases.