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Smithsonian Natural History Museum

Smithsonian Natural History Museum

Smithsonian Natural History Museum

update 102213

Triassic Map Click on figures The Early Triassic is dominated by the plants and animals that had survived the Late Permian extinction.  Dicynodonts especially Lystrosaurus are the most common members of every land based community and to a lesser extent the early Cynodont Thrinaxodon.  Lystrosaurus has been found on every continent including Antarctica. It was an important part of proving the theory of continental drift. Triassic Seas the great families of aquatic reptiles evolved. During this time the modern sea fauna is established. Late Triassic American southwest One of the last stands of Placerias is the American southwest. Triassic Europe Prosauropods are the most common dinosaurs from latest Triassic to the end of the Early Jurassic. The best information about the Triassic Dinosaurs comes from South America

The Mesozoic starts in the Early Triassic 248 million years ago. The world continent Pangaea was still intact without major impediments to movement of animals population.  

Early Triassic is dominated by the plants and animals that had survived the Late Permian extinction. Medium size Cynodonts and Dicynodonts are common, as are amphibians.

Middle Triassic, is a period of transition as dicynodonts and cynodonts whose ancestors dominated the Late Permian decline and archosaurs the ancestors of dinosaurs and crocodiles experiment with a variety of plant eating and carnivorous forms. Archosaurus become the large and medium predators, dicynodonts are the large and medium herbivores, aetosaurs and cynodonts are medium to smalll herbivores.

Late Triassic, dinosaurs up with the start of the cycadoid conifer flora that replaces the remaining Paleozoic flora. The climate was characterized by extreme aridity alternating with megamonsoons. Sauropodamorphs and small ceratosaurs being the best known dinosaurs but there are lots of other interesting creatures.

Dicroidim-dominated flora remained established in the southern hemisphere, while in the northern hemisphere the Late Triassic saw a rise in a group of seed-bearing conifers called the Cheirolepidiaceae

 The last of the archosaurs and dicynodonts die out in the final extinction at the end of the Triassic leaving the dinosaurs to fill the world. The best information about the Triassic Dinosaurs comes from South America with Argentina producing most of the early finds.  Speculation about low oxygen levels may be the key to the dominance of dinosaurs at this time. The avian style lung systems would have been a major advantage. Large size is an advantage in today’s deserts and with flora of low fund value. The tailed Rhamphorynchoids appeared in the Triassic and flourished until the Late Jurassic. Eoraptor is considered the most primitive dinosaur and close to the ancestor of the whole family. Pisanosaurus the earliest known ornithiscian also is from South America. In Europe Triassic finds are scrappy. In Africa, Madagascar has produced interesting finds. The earliest known prosauropods have been reported there but have not yet been described. The earliest sauropods, Isanosaurus in Thailand and the current oldest Antetonitrus ingenipes from South Africa show up in the Triassic. Some combination of climate and flora seems to have favored the prosauropods. Sauropods don't take off until the Middle Jurassic when climate and plants change.

The Late Triassic is divided in the

Carnian, climate was mostly arid in the tropicsbut was interrupted by the markedly more humid conditions of the Carnian Pluvial Event. This coincided with the radation of dinosaurs. The earliest dinosaur Eoraptor originated slightly before the Carnian stage began around 230 Ma. The oldest dinosaurian assemblage, the Ischigualasto Formation of Argentina. The land-sea distribution led to "mega-monsoons".

Norian, The Norian began as a world dominated by typically Carnian archosauromorphs. It is marked by the sucess of of sauropodomorphs and ceolophysid theropds.
Phytosaur-Aetosaur-Metoposaur vertebrate fossil assemblage of the west Chinle
capitosaur-prosauropod-turtle fauna of Europe and Greenland
Ghost Ranch, New Mexico The South African Lower Elliot Formation has sauropodomorphs, the earliest known true sauropods
Los Colorados of Argentina Riojasuchus ornithosuchids

 

Rhaetian, Continuation of the rule of the dinosaurs among the megaherbivores that began in the late Norian.
(nothosaurs and shastosaurs) with the classic dolphin-like ichthyosaurs and "Nessie"-style plesiosaurs.ended with a mass-extinction all non-dinosaurian and non-crocodylomorph archosaurs
ecosystems are sauropodomorph dominated.
England small sauropodomorphs Terrestrisuchus
Laurasia
abundant herbivore Plateosaurus, a dinosaur that persists into the Rhaetian, as do the plagiosaurs and phytosaurs that co-exist Gondwana

Argentinean Los Colorados diverse large sauropodomorphs

 

BBC produced Walking with Dinosaurs with an excellent graphics the Triassic installment was called the New Blood. The Triassic Seas were a time of great change as the great families of aquatic reptiles evolved. During this time the modern sea fauna is established.

 

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