Pentaceratops was a rhinoceros-like dinosaur. It walked on four sturdy legs and had three horns on its face along with a large bony plate projecting from the back of its skull (a frill). One upward-pointing horn above its parrot-like beak and two longer, forward-pointing horns above its eyes probably provided protection from predators, and were possibly used in mating rivalry and rituals. It also had two enlarged, horn-like cheekbones that protruded from its face. It had a very large skull, 9.8 feet (3 m) long, with a very large, bony, scalloped, head frill. It has the largest-known skull ever found (for a land-dwelling animal).
Pentaceratops was about was up to 28 feet (8 m) long, roughly 10 feet tall (3 m), and weighed up to 8 tons. It had a short, pointed tail, a bulky body, column-like legs with hoof-like claws, and a bony, scalloped neck frill rimmed with bony points. It had a parrot-like beak, many cheek teeth, and powerful jaws. Pentaceratops hatched from eggs.
Kronosaurus was a short-necked plesiosaur, a meat-eating marine reptile 30 feet (9 m) long. It had four flippers, a huge head with strong jaws, and a short, pointed tail. The head was up to 9 feet (2.7 m) long, about 1/3 of the entire length of the body. It had rounded teeth at the back of the jaws which could crush shells and cephalopods (squid and octopi).
Kronosaurus was not a dinosaur, but a plesiosaur, another type of extinct reptile. Plesiosaurs may have evolved from the Nothosaurs or the Pistosaurus, a mid-Triassic reptile.
Euparkeria is an extinct genus of reptiles that may have been ancestral to the major reptilian groups of the Mesozoic era; specimens are found as fossils in Early Triassic rocks of South Africa (245 to 240 million years ago). Euparkeria was about 1 m (3 feet) long and lightly built. It probably was equally adept at progressing on all four limbs or with the body balanced on the hind legs; the hind limbs were longer and stronger than the forelimbs. Many of the bones were hollow; the very long tail served as a counterbalance when the animal stood upright. The skull was slender and light, with many sharp, well-developed teeth in the margins of the jaws and on the palate as well, a primitive feature.
Daspletosaurus (dahs-PLEE-toh-sawr-us) meaning "frightful lizard", because of its fearsome teeth (Greek daspletos = frightful + sauros = lizard), was theropod dinosaur, which had a head as large as the later Tyrannosaurus rex, with just as vicious teeth. With such large teeth, this carnivorous dinosaur may have been able to attack and kill heavily plated species of dinosaurs, like ankylosaurs. A contempary of Gorgosaurus, Daspletosaurus was founded on a skeleton originally believed to be an undescribed species of Gorgosaurus. Russell
hypothesized that while the more lightly built and more common Gorgosaurus may have
specialized in preying on the more common species of hadrosaurids, the heavier, more robust Daspletosaurus may have
specialized in the less prevalent armored species of the time such as the ceratopsids.