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The BBC’s video series Walking with Dinosaurs is an unparalleled attempt to enlighten the general public about life in the Mesozoic Era.  The producers tried to use current scientific knowledge to create realistic situations that could have occurred during the reign of the dinosaurs.  Exquisite computer graphics combined with state-of-the-art puppetry to create lifelike visuals to accompany the narration.  Numerous species of dinosaurs and Mesozoic reptiles were described ranging from land based predators and herbivores to aquatic reptiles and flying pterosaurs.  Even with all scientists know about the Mesozoic, the makers of Walking with Dinosaurs had to make some educated guesses throughout the film.

            The first dinosaur to make an appearance in the film was Coelophysis, a small reptile that had adapted for killing.  Coelophysis made its appearance about 220 MYA in the Early Triassic Period of the Mesozoic Era.  It had specialized hips and ankles that made it and agile runner.  Because of their small size, Coelophysis hunted in groups to take down larger prey.  In the movie Coelophysis is shown in an arid climate where, unlike the other reptiles shown, it was thriving.  One of the conjectures of the makers of the film was that Coelophysis had adapted to arid environments to fill a new niche.  One of these adaptations was that Coelophysis would lose little water when excreting, unlike other contemporary reptiles.

            Another Early Triassic dinosaur was Plateosaurus.  At up to four tons this dinosaur embraced the idea that “size is key to success.”  Plateosaurus was an herbivore and likely an ancestor of the sauropods.  It could also reach high vegetation that no other reptile at the time could.  Placerias was another Early Triassic reptile, but it was not a dinosaur.  It was a large herbivore that was equipped with two tusks used mostly for digging up roots, but could also be used for defense.  Postosuchus was the largest predator of the Early Triassic but like Placerias it was not a dinosaur.  It was a heavily built and slow moving predator that depended on ambushing its prey.  Another member of the Early Triassic was Peteinosaurus, the first flying reptile.  Its hollow bones and simple wings were evolutionary novelties that allowed it to become the first flying reptile.

            The Jurassic Period saw a great diversification of the dinosaurs.  Allosaurus was the dominant predator of the Jurassic Period.  Much larger than most other predators, Allosaurus was designed for bringing down large prey like sauropods.  It walked on two legs and used its large jaw, small arms, and large feet as weapons.  In Walking with Dinosaurs Allosaurus is shown as being a group hunter, which was probably conjectured.  Another Jurassic predator was Ornitholestes.  Much smaller than Allosaurus, Ornitholestes lived deep in forests where it hunted lizards and small mammals.  However, as shown in the movie, it probably would also eat eggs if given the opportunity.

            The Jurassic Period also saw the development of the sauropods.  Diplodocus, the feature of one of the installments, was the longest sauropods.  Also called the “suspension bridge dinosaur” its head and neck were held horizontally out from the body very close to the ground.  Like other sauropods, Diplodocus was a herding animal finding safety in numbers.  Its teeth were designed to quickly strip branches of their leaves.  In order to cope with the lack of chewing, Diplodocus would ingest stones to aid in grinding of plant material.  Because of its large size, Diplodocus needed to eat a lot of food every day; in fact, it would drop about one ton of dung every day.  In Walking with Dinosaurs the creators would have speculated about all of the behavior seen in Diplodocus including mating rituals, how young Diplodoci survived, and the use of tails for communication in the herd.

            Other dinosaurs of the Jurassic included Brachiosaurus, another sauropod.  Unlike Diplodocus, Brachiosaurus’s heads were held upright.  In addition, Brachiosaurus’s front legs were longer than its rear legs giving it extra height, up to thirteen meters.  This allowed it to eat vegetation at the treetops that no other animal could reach.  Another unique dinosaur was Stegosaurus.  This herbivore had dorsal plates along its spine that could be engorged with blood.  It was likely that these plates were used to attract mates, frighten predators, and help in thermal regulation.  Stegosaurus also had two sets of spikes on its tail that it could use as a weapon for self-defense.  It is worthwhile to mention that Stegosaurus had one of the smallest brain-to-body ratios of all the dinosaurs.

            The Jurassic Period was also a time when marine reptiles flourished.  Ophthalmosaurus was one of the earliest marine reptiles.  Shaped very much like a fish, it had huge eyes which were likely used to hunt animals like squid deep in the ocean.  It also gave live births and breathed air, which was shown as a disadvantage in Walking with Dinosaurs.  Another important marine reptile was Liopleurodon, at up to 125 tons it was the largest carnivore ever.  One of its conjectured behaviors was that it was very territorial.  This is likely because a predator that large would have needed an enormous range to maintain itself.

            Rhamphorhynchus was a small pterosaur that made its appearance during the Jurassic Period.  It lived primarily on a diet of insects.  Rhamphorhynchus is interesting because it is likely that it lived on the backs of sauropods, like some birds live on elephants today.  This is a unique symbiotic relationship that benefits both animals.  Rhamphorhynchus has a place to live and it eats the insects and parasites that would otherwise plague a large sauropod.

            The Cretaceous Period was the final period of the Mesozoic Era and it was during this time that flying reptiles reached their zenith.  The Tapejara was one of these flying reptiles.  Similar to many other reptiles, the Tapejara had a crest on its skull probably used to attract mates.  However, the largest flying reptile of the Cretaceous was the Ornithocheirus.  Capable of worldwide migrations it took advantage of warm air updrafts over land and ocean.  Its wings were flaps of skin extending from the fingers to the feet.  Unlike modern birds, Ornithocheirus did not have feathers but it did have a fine downy fur covering its body.  In Walking with Dinosaurs the creators had to predict all of the behavior of Ornithocheirus, especially the mating rituals.

            Another interesting symbiotic relationship was between Iguanodon and Polacanthus.  Iguanodon was a herding herbivore with specialized teeth that made it the first dinosaur that could chew.  Polacanthus was a solitary nodosaur with spikes lining its back for protection.  Herds of Iguanodon were accompanied by a solitary Polacanthus finding safety in numbers.

            The Cretaceous also saw the rise of the Dromaeosaurs, specifically Utahraptor the largest Dromaeosaur.  Armed with a mouthful of serrated teeth, sharp claws, and a large slashing claw on each foot they were a formidable predator.  Utahraptors hunted in packs to take down large prey.  Scientists also believe that raptors had a social order in their herds.

            Dinosaurs adapted to all environments during the Mesozoic, including Antarctica which was frozen for half of the year.  Muttaburrasaurus was a migratory herbivore that moved into Antarctica during the summer.  It was a herding dinosaur with a distinctive muzzle probably capable of producing loud calls.  Another Antarctic native is the Polar Allosaurus.  Smaller than a normal Allosaurus, it was the largest predator in Antarctica.  Koolasuchus was a Cretaceous amphibian, but it was another major predator in Antarctica.  During the summer it would live in the water, but during the freezing winters it would move into the forest to hibernate.  It was a major competitor with crocodiles during the Cretaceous.

            Leaellynasaurs were another Cretaceous inhabitant of Antarctica.  About one meter tall, it was probably well suited for living in the extreme cold of the Antarctic winter.  Leaellynasaurs had large eyes that could see well during the four months of darkness.  Like raptors, scientists believe Leaellynasaurs lived in clans with social hierarchies.  The creators of Walking with Dinosaurs had to hypothesize about the behavior of Leaellynasaurs including how they dealt with the freezing temperatures during winter.

            Toward the end of the Cretaceous Period, many of the most popular dinosaurs evolved.  Armed with a huge jaw full of serrated teeth, Tyrannosaurus was the dominant predator of the late Cretaceous.  Scientists believe that Tyrannosaurs were very maternal dinosaurs, raising their young from eggs until they were self-sufficient.  Like many other species, Tyrannosaurs also exhibit sexual dimorphism with females larger than males.

            The Ceratopsian Torosaurus was a late Cretaceous herbivore.  It was a herding animal bearing two large post-orbital horns, one small nose horn, and a large frill.  The frill had two large fenestra which lead scientists to believe it was used predominantly for display: to attract mates and to scare away predators.  Another Cretaceous herbivore, although less common than Torosaurus, was Ankylosaurus.  Covered with bony plates and armed with a bony club at the end of its tail, Ankylosaurus was a very defensive dinosaur.  They were solitary animals that traded speed and agility for armor.  Ankylosaurs also had a very small brain-to-body ratio.

            In addition to those already listed, the creators of Walking with Dinosaurs had to make many inferences about life in the Mesozoic Era.  Skin texture and coloring is almost entirely subjective.  The only references scientists have are a few samples of fossilized dinosaur skin.  All of the behavior of the reptiles shown was inferred from anatomical considerations and the behaviors of modern animals.  The purpose of some anatomical features is also unknown.  Nasal passages and large crests are thought to have had a role in the production of distinctive sounds for each species.  The existence of social hierarchies in herding animals is an educated hypothesis based on modern observations.