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The Mesozoic Era [3] is the era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Periods.It is characterized by the dominance of gymnosperms such as cycads, ginkgoaceae and araucarian conifers, and of archosaurian reptiles such as the dinosaurs; a hot greenhouse climate; and the tectonic break-up of Pangaea.
The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic), but little is known about them. The continental masses of the Mesoproterozoic were more or less the same ones that exist today, although their arrangement on the ...
Mesozoa were once thought to be evolutionary intermediate forms between Protozoans and Metazoans, but now they are thought to be degenerate or simplified metazoa.Their ciliated larvae are similar to the miracidium of trematodes, and their internal multiplication is similar to what happens in the sporocysts of trematodes.
The mode of Mesozoic dinosaur body masses is between 1 and 10 metric tons (1.1 and 11.0 short tons). [139] This contrasts sharply with the average size of Cenozoic mammals, estimated by the National Museum of Natural History as about 2 to 5 kg (4.4 to 11.0 lb). [140] The sauropods were the largest and heaviest dinosaurs.
Penfield published a letter in Natural History objecting to Hildebrand's claim to have identified the Chicxulub Crater as "ground zero" to the end-Cretaceous mass extinction. He pointed out that he proposed that very hypothesis back in 1981. [24] Pope and others finally published their research that had been "scooped" by Hildebrand and Boynton ...
The Proterozoic Eon was a very tectonically active period in the Earth's history. Oxygen changed the chemistry allowing for extensive geological changes. Volcanism was also extensive resulting in more geologic changes. The late Archean Eon to Early Proterozoic Eon corresponds to a period of increasing crustal recycling, suggesting subduction.
Following the Permian–Triassic extinction event, the most devastating of all mass-extinctions, life recovered slowly.In the Middle Triassic, many groups of organisms reached higher diversity again, such as the marine reptiles (e.g. ichthyosaurs, sauropterygians, thallatosaurs), ray-finned fish and many invertebrate groups like molluscs (ammonoids, bivalves, gastropods).
The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic–Jurassic extinction event, 201.3 Ma (million years ago), and ends at the start of the Middle Jurassic 174.7 ±0.8 Ma.