Dinosaurs (means in Greek “terrible lizard”) were a specific group of reptiles that lived on land, had upright leg posture (legs directly under their bodies). They include both herbivores and carnivores. They ranged from tiny feathered species to massive long-necked giants, and birds are their direct descendants.
Pangea was formed 335 millon years ago, during the Carboniferous. It started separating on the Early Jurassic (200 to 180 million years ago), starting dividing in two big mases: Laurasia (North America, Europe and Asia), and Gondwana (South America, Africa, Antartica, India, and Australia)
The Apatosaurus (meaning “engañoso lizard” in Greek) Jurásico tardío (~150 millones de años), Norteamérica
The Triadobatrachus (meaning approximately “Triassic frog” in Greek) lived during the early Triassic, 250 million years ago in Madagascar.
The Triceratops (meaning “three-corns face” in Greek) was a lived in North America over 68 to 66 millon years ago.
The Tyrannosaurus rex (meaning in “King tyran lizard” in Greek and Latin) lived during the Late Cretacius Period (over 68 to 66 millon years ago) in North America.
The Scolosaurus (meaning “spiked lizard” in Greek) lived over 76 to 75 million years ago in North America. He was an anquilosaur (armored dinosaur), quadrupedous, covered by bone placas (osteoderms) and a tail finished in a kind of boned maza used as a defense.
The Saurolophus (meaning “crested lizard” in Greek) Cretácico tardío (~70 millones de años), Norteamérica y Asia
The Stegosaurus (meaning “roofed lizard” in Greek) lived during the late Jurassic Period, 155 to 150 million years ago in North America. It was a quadrupedan herbivorous, with a two hileras of triangular bone placas and four sharped spikes in the tail, called “thagomizer”. It is famous to have a brain with the size of a nut.
The Pteranodon (meaning “wing without theeth” in Greek) wasn’t a dinosaur, but a flying lizard mmmmm lived during the Late Cretacian (over 84 to 86 million years ago)
Many species were huge,
🌡️ Warm, humid climate:
- No polar ice caps = more water available globally
- Natural greenhouse effect (high CO₂ levels)
- Global temperatures 6-8°C warmer than today
- Year-round growing seasons even at high latitudes
🌱 Explosion of primary producers:
- Dense forests of conifers, ferns, and cycads
- First flowering plants = increased plant diversity
- Higher oxygen levels in atmosphere (up to 35% vs 21% today)
- Massive plant biomass = abundant food sources
🦕 Advantages of gigantism:
- Thermoregulation = easier to maintain body temperature (large bodies lose heat more slowly)
- Predator avoidance = fewer predators can attack giants
- Resource access = reach high tree canopies that smaller animals can’t
- Metabolic efficiency = lower relative energy costs per kilogram of body weight
- Digestive advantages = longer gut retention time for processing tough plant material
🌍 Geological factors:
- Shallow seas covered much of the continents = more coastal habitats
- Stable continental positions = consistent climate patterns
- Abundant mineral nutrients from volcanic activity
🔄 Evolutionary arms race:
- Predator-prey escalation = bigger herbivores needed bigger predators
- Competition for resources = size advantage in reaching food
- Sexual selection = larger individuals had mating advantages
Dinosaurs
The Apatosaurus (Apatosaurus louisae) was a massive long-necked sauropod dinosaur that lived during the Late Jurassic period. It could reach lengths of up to 23 meters and weighed around 16-22 tons, feeding on ferns, conifers, and other vegetation.
The Triceratops (Triceratops horridus) was a large herbivorous ceratopsian dinosaur known for its distinctive three facial horns and large bony frill. It lived during the Late Cretaceous period and could weigh up to 12 tons.
The Saurolophus (Saurolophus osborni) was a duck-billed hadrosaur dinosaur that lived during the Late Cretaceous period. It was characterized by its distinctive backward-pointing cranial crest and could reach lengths of up to 12 meters.
The Stegosaurus (Stegosaurus stenops) was an armored herbivorous dinosaur from the Late Jurassic period, famous for its distinctive double row of plates along its back and four sharp spikes on its tail called a “thagomizer.”
The Tyrannosaurus (Tyrannosaurus rex) was one of the largest land predators ever known, living during the Late Cretaceous period. It could reach lengths of 12-13 meters and had powerful jaws with teeth up to 20 cm long.
The Deinonychus (Deinonychus antirrhopus) was a medium-sized raptor dinosaur from the Early Cretaceous period, known for its large sickle-shaped claw on each foot and its likely pack-hunting behavior.
Non-dinosaurs
The Pteranodon (Pteranodon longiceps) was a flying reptile (pterosaur), not a dinosaur. It lived during the Late Cretaceous period and had a wingspan of up to 7 meters, making it one of the largest flying animals ever.
The Triadobatrachus (Triadobatrachus massinoti) was an early amphibian, not a dinosaur. It lived during the Early Triassic period (about 250 million years ago) and is considered a transitional form between frogs and their ancestors.