208-188 Million Years Ago

 

The Early Jurassic (in geology referred to as the Lower Jurassic, originally (and still in Europe) the "Lias") is the earliest of three time scales of the Jurassic period.

The dinosaurs have attained dominance, while most of the  other Triassic types of animals have died out in two major Triassic extinctions - the mid-Carnian and the terminal Rhaetic.  Apart from one or two early types, the dinosaurs seem to have been unaffected by these extinction events.

As the Jurassic Period opened, Italy, Greece, Turkey, and Iran were attached to the North African portion of Gondwanaland.  The climate was warm and moister than during the Triassic.  Reptiles were the dominant form of animal life and experienced a great adaptive radiation.  In the oceans various types of ichthyosaurs and plesiosaurs evolved. 

In the air the pterosaurs began to diversify.  On land many Triassic dinosaurs (prosauropod herbivores and coelophysid carnivores) continued, while a number of new forms (giant sauropods and armoured scelidosaurs) evolved.  Under the feet of the dinosaurs rodent-like tritylodontid Therapsids co-existed with primitive shrew-like mammals and lizard-like sphenodont reptiles.  Crocodiles appeared also, but they were mostly aquatic forms.

During the early Jurassic then, evolution seems to have polarised: on the one hand there were the ruling land animals, the great dinosaurs, which filled the ecological roles now taken up by medium-sized and large mammals; on the other hand the first mammals had appeared, and together with the tritylodont Therapsids they filled the small rodent and insectivore niche.  The mammals were to remain small and individually insignificant - comparable to shrews, mice and rats of today - although doubtless  very significant ecologically, for the 135 million years of the dinosaurs reign.

Dinosaurs of the Lower Jurassic include:

Barapasaurus | Ammosaurus | Vulcanodon | Kotasaurus

Precambrian | Cambrian | Ordovician | Silurian | Devonian | Carboniferous | Permian | Upper Triassic | Lower Jurassic | Middle Jurassic | Upper Jurassic | Lower Cretaceous | Upper Cretaceous