Sauropodomorphs

THE SAUROPODOMORPHA ("lizard-feet forms.")

were herbivorous, usually quadrupedal (four-footed)

dinosaurs. A clade within Saurischia, they were 

characterized by small heads, bulky bodies, and

long necks and tails. Sauropodomorphs have

often been split into two groups: prosauropods

and sauropods. Prosauropods lived from Late

Triassic to Early Jurassic times (225-180 million years ago) and

included beats such as the small Anchisaurus and one of the first

very large dinosaurs, Plateosaurus. By Middle Jurassic times (about

165 million years ago), sauropods had replaced prosauropods and

spread worldwide. They included the heaviest and longest land animals

ever, such as Diplodocus and Brachiosaurus. 

Brachiosaurus

Sauropods persisted to the 

end of the Cretaceous period (65 million years ago). Many of these

huge bulk and powerful tails, which they could use to lash out at

attackers. Sauropodomorphs were the most common large

herbivores until Late Jurassic times (about 145 million years ago),

and appear to have survived in both southern and

northern continents until the end of the Cretaceous period.

Theropods

AN ENORMOUSLY SUCCESSFUL SUBGROUP of the Saurischia,

 the bipedal (two-footed) theropods (“beast feet”) emerged 

230 million years ago in Late Triassic times; the oldest known

Example comes from South America.

Fossil Skeleton of Archaeopteryx

Theropods spanned the age of

most dinosaurs (230-65 million years ago) and beyond, and included

most of the known predatory dinosaurs. The typical theropod had smallish

arms with sharp teeth; an S-shaped neck; long, muscular hind limbs;

and clawed, usually four-toed feet. Many theropods may have been

warm-blooded; most were exclusively carnivorous. Theropods ranged

from Tyrannosaurus and Baryonyx. The group also included 

ostrich-like omnivorous and herbivores with toothless breaks,

such as Struthiomimus and Gallimimus. Birds are dinosaurs and evolved

from within a group of tetanuran theropods called maniraptorans.

Archaeopteryx, small and feathered, was the first known bird and lived

Alongside other Dinosaurs.