TheLower Triassic is the first of threeepochs of theTriassicperiod. It lasted from about 252.2 million years ago (mya) to ~247.2 mya. The Lower Triassic is the oldest epoch of theMesozoicera. These rocks were laid down just after the greatPermian–Triassic extinction event.
The Lower Triassic was called theScythian stage, which can be found in older literature. InEurope, most of the Lower Triassic is composed ofsandstone. It is alithostratigraphic unit ofcontinentalred beds. They were formed on land underdesert conditions.
The massive extinctions that ended thePaleozoicera caused extreme hardship for the surviving species. Many types ofcorals,brachiopods,molluscs,echinoderms, and otherinvertebrates had completely disappeared. The most common hard-shelled marine invertebrates werebivalves,gastropods,ammonites,echinoids, and a few articulatebrachiopods. The most common land animal was the herbivoroussynapsidLystrosaurus.
The earliest Triassicfaunas lackedbiodiversity and were like that throughout the epoch. Recovery on land took 30 million years.[1]
The firstichthyosaurs evolved in this epoch. The largest ichthyosaurs known come from the Triassic.
The climate during the Lower Triassic (especially in the interior of the supercontinentPangaea) was generally dry. Deserts were widespread. The poles had atemperate climate. The relatively hot climate of the epoch may have been caused by widespreadvolcanic eruptions.
On land, the plants included thelycophytes, the dominantcycadophytes,ginkgophyta (represented in modern times byGinkgo biloba),ferns,horsetails andglossopteris.
