Geologic time scale Reference Libraries
Image Caption: Head of Tenontosaurus, Institut de paléontologie humaine, Paris, France. Credit: Rémih/Wikipedia (CC BY-SA 3.0) Tenontosaurus, meaning “sinew lizard”, is a genus of medium to large sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceious period sediments of western North America, dating roughly between 115 to 108 million...
The Neoproterozoic is the third of three subdivisions of the Proterozoic Eon (occurring from 1 billion years ago to 542 million years ago). This terminal era of the Proterozoic is itself divided into three sub-periods called the Tonian, Cryogenian, and Ediacaran Periods. The most severe glaciation known in the geologic record occurred during the Cryogenian Period, when ice sheets reached the...
The Paleoproterozoic is the first of three subdivisions of the Proterozoic Eon (occurring from 2.5 billion to 1.6 billion years ago (Ga). This period is marked by the first stabilization of the continents, and also when cyanobacteria--a type of bacteria that uses biochemical processes of photosynthesis to produce oxygen--evolved. Experts have found paleontological evidence that during at...
The Archean (formerly Archaeozoic) is a geologic eon between the Hadean and Proterozoic eons. The Archean Eon begins at roughly 3.8 billion years ago (Ga) and ends at about 2.5 Ga. But unlike all other geological ages, which are based on stratigraphy, The Archean eon is defined chronometrically. The lower boundary of 3.8 Ga has also not been officially recognized by the International Commission...
The Hadean is the unofficial geological period of time that lies just before the Archean time period. The Hadean began with the formation of the Earth roughly 4.5 billion years ago (Ga) and ended about 3.8 Ga; the latter date varies according to different sources. Hadean is derived from Hades, Greek for “underworld,” referring to the hellish conditions on the planet at the time. The term...
Sharpirhynchia sharpi is a species of extinct brachiopod named after fossil collector Samuel Sharp (1814-1882). This species lived during the Lower Bathonian of the Middle Jurassic Period. It is found only in the United Kingdom, and numerous specimens have been taken from several sites, the first from Limekiln Quarry in Northampton, England. S. sharpi is roughly a half-inch long, with a...
Sauroposeidon, meaning “earthquake god lizard,” is a genus of sauropods dinosaur from the Aptian and Albian ages of the Early Cretaceous Period (110 million years ago). It was discovered in the southeast region of Atoka County, Oklahoma, not far from the border of Texas, in a claystone outcrop. The fossils were initially misidentified as pieces of petrified wood when they were found in...
Qiaowanlong is a genus of sauropod dinosaur from the Albian stage of the Early Cretaceous Period (100 million years ago). It was discovered in the Yujinzi Basin of Gansu, China in 2007. It came from the geological formation called the Xinminpu Group. Qiaowanlong is known from articulated cervical (neck) vertebrae and a right pelvic girdle, as well as several unidentified bone fragments. It...
Qantassaurus is a genus of ornithopod dinosaur from the late Aptian to early Albian age of the Early Cretaceous Period (115 million years ago). It lived in Australia when the continent was still south of the Antarctic Circle, and was still part of the supercontinent Gondwana. Qantassaurus was discovered in 1996 during the third annual field season of the Dinosaur Dreaming Project, a dig...
Sonorasaurus, meaning "Sonora lizard," is a genus of brachiosaurid dinosaur from the Albian to Cenomanian stages of the Mid Cretaceous Period (112 to 93 million years ago). Its name was derived from the Sonoran Desert in Arizona where its fossils were first found. The remains were discovered by geology student Richard Thompson, in 1995. Dating of the discovery makes Sonorasaurus the first...
