We start at the end of the Paleozoic, after a mass extinction that wiped out most terrestrial and aquatic life called the Great Dying. After this mass extinction Earth’s continents were almost done merging into a super continent called Pangea, this meant almost all land was connected and this allowed the terrestrial survivors to spread out. The Mesozoic is divided into 3 major periods called the Cretaceous, Jurassic and the Triassic. Each period spread over millions of years and had different but diverse wildlife. There were also a few large oceans like the Tethys ocean and the Panthalassa, each later in the Mesozoic harbored many large ocean predators and allowed many new species to evolve.
The first Period was the Triassic which spanned from 251.9-201.3 mya (Million years ago), the Triassic was known for its hot, dry climate and it is known as the time Dinosaurs first evolved. At the beginning of the Triassic, the survivors of the great dying found a planet ready for life again. There were Early mammalian predators known as Cynodonts that hunted during the early Triassic. Dinosaurs, or their oldest ancestors, were quite small and even later in the Triassic they didn’t grow to the size seen later in the Mesozoic. Some early dinosaurs were the: Coelophysis, Isanosaurus, Camposaurus, Chindesaurus, and Plateosaurus. These dinosaurs were early types of well known dinosaurs like early sauropods or theropods. The mid to late Triassic saw Pangea starting to break apart, more evolution of the early dinosaurs, mammals and pterosaurs, and more. The plant life in the Triassic was dominated by Cycads, Conifers, Ferns, and Ginkgoes. The Triassic culminated in an extinction event which resulted in the loss of many marine and terrestrial species.
The Second period was the Jurassic (201.3-145 mya) which was known for the flourishing of large dinosaurs, the break up of the super continent Pangea, and the appearance of early birds. Early Jurassic dinosaurs could grow much larger than Triassic animals like the Sarcosaurus which grew to 3.5 meters in length or around 10 ft. There were new Pterosaurs in the Jurassic (keep in mind pterosaurs are NOT dinosaurs), like the Dimorphodon, Pterodactylus, Rhamphorhynchus, and Dearc. Sauropods fully evolved during the Jurassic period and could reach ridiculous sizes. Sauropods like Brachiosaurus or Apatosaurus and other sauropods persisted through the Jurassic and into the Cretaceous. The early bird Archaeopteryx evolved during the Jurassic and other iconic dinosaurs like the Stegosaurus and Kentrosaurus evolved with the Archaeopteryx. Many predatory theropods evolved like the Allosaurus. Jurassic plant life wasn’t much different from the Triassic’s but at the end of the Jurassic flowering plants emerged, a whole new species of plant.
The Third and last period was the Cretaceous period (145-66 mya) known for flowering plants and the mass extinction that ended the dinosaur reign, the Cretaceous period was home to many icons in the dinosaur world. Early-mid Cretaceous dinosaurs include Protoceratops, Utahraptor, Oviraptor, Therizinosaurus, and Velociraptor. Plant life during the Cretaceous was mostly dominated by flowering plants with ginkgoes, cycads and ferns still persisting through the start of the Mesozoic. During the mid Cretaceous there was a small extinction that wiped out the Icthyosaurs, paving the way for mosasaurs to rise to the top of the Marine ecosystem. In the late Cretaceous other dinosaurs evolved like the T-rex and Triceratops. At the end of the Cretaceous a mass extinction that wiped out the dinosaurs occurred, called the K-pg extinction event. Which was caused by a 10-15 kilometer asteroid smashing into the world sending ash and other debris into the air. The debris blocked the sun and caused large plants to die and plant eating dinosaurs and the dinosaurs that ate those dinosaurs died. The result of the asteroid was the extinction of the dinosaurs and the rise of Mammals.
Related Stories:
https://www.usgs.gov/youth-and-education-in-science/mesozoic
https://www.britannica.com/science/Mesozoic-Era
https://ucmp.berkeley.edu/mesozoic/mesozoic.html
https://www.amnh.org/dinosaurs/types-of-dinosaurs
https://www.nps.gov/articles/000/mesozoic-era.htm
Take Action:
Support the Smithsonian and their dinosaur exhibit to preserve the fossils of the great creatures:
https://naturalhistory.si.edu/
Get a book going in depth about some of the Mesozoic animals and plants:
https://www.barnesandnoble.com/w/dinosaur-empire-abby-howard/1126009550
