The Dinosaurs of the Triassic Period: A Summary of the First Dinosaurs and their Rise to Dominance
CHimerasuchus・39 minutes read
The Mesozoic Era spanned 186 million years and was divided into three periods; Triassic, Jurassic, and Cretaceous, with dinosaurs evolving and growing in size through these periods to dominate the world. The rise of dinosaurs during the Triassic was opportunistic, taking over niches left vacant by extinctions caused by volcanic activity, leading to their eventual dominance in the Jurassic and Cretaceous periods.
Insights
- The Triassic period marked the emergence of the first dinosaurs, which were overshadowed by later, more famous Jurassic and Cretaceous species, highlighting the importance of this initial era in dinosaur evolution.
- The rise of dinosaurs during the Triassic was opportunistic, with these creatures taking over ecological niches left vacant by extinctions caused by volcanic activity, leading to their eventual dominance, showcasing the adaptability and resilience of these ancient reptiles.
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Recent questions
What characterized the Triassic period?
Pangea, high temperatures, and arid climates.
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Summary
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Triassic Era: Overlooked Dinosaurs and Ancient World
- The Mesozoic Era, known as the age of reptiles, was divided into three periods: Triassic, Jurassic, and Cretaceous, spanning 186 million years.
- Dinosaurs did not dominate during the Triassic period, evolving and growing in size by the early Jurassic period.
- Triassic dinosaurs are often overlooked in media, overshadowed by more famous Jurassic and Cretaceous species.
- The Triassic world was vastly different from today, with Pangea as a single landmass, higher global temperatures, and arid climates.
- The first dinosaurs coexisted with conifers, cycads, and ferns, as modern angiosperms had not yet evolved.
- Synapsids, proto-mammals, were dominant during the early Triassic, with diverse groups like dicynodonts and cynodonts.
- Archosauromorphs, reptiles related to dinosaurs and crocodilians, diversified during the Triassic, including herbivores and apex predators.
- Pseudosuchians, distant relatives of crocodilians, were diverse during the Triassic, resembling dinosaurs and filling similar niches.
- The first dinosaurs, like Eodromeus, were small predators with five fingers, evolving alongside other archosaurs and ornithodirans.
- The relationships between the three major dinosaur clades - Theropoda, Sauropodomorpha, and Ornithischia - remain debated, with Herrerasaurs considered early diverging saurischians.
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Triassic Theropods and Prosauropods: Evolution and Diversity
- The Triassic period saw the emergence of numerous unambiguous theropods, all belonging to the smaller neotheropoda group.
- Coelophysis, a famous Triassic theropod, was found in the Chinle Formation in the southwestern United States, with over a thousand skeletons discovered at Ghost Ranch.
- Coelophysis, built for speed and agility, had a slender skull and was nocturnal, unlike larger contemporaries like Postosuchus.
- Triassic theropods, like Coelophysis, were primarily nocturnal in equatorial low latitudes but could hunt day or night in cooler high latitudes.
- Zupaysaurus, a large early theropod, coexisted with the massive pseudosuchian predator, Vasolasuchus, in Argentina.
- Thecodontosaurus, a late Triassic herbivore, was evolutionarily between small sauropodomorphs and dominant prosauropods.
- Prosauropods, like Macrocollum, had long necks for tree browsing, small heads to avoid neck strain, and large hand claws for defense or manipulating branches.
- The largest Triassic prosauropods, like Lessemsaurus, reached lengths of 10 meters and weighed up to 10 tons, exceeding contemporary animals.
- Most prosauropods were obligate bipeds, with only a few, like Melanorosaurus, capable of walking on all fours with flexed limbs.
- Platiosaurus, a widespread Triassic sauropodomorph, lived in herds and ranged from the southern to northern hemispheres, reaching lengths of 10 meters and weights of 4 tons.
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Evolution of early ornithischian dinosaurs
- Silosaurs are considered basal ornithischian dinosaurs, resembling aphanosaurs but with longer legs and a more graceful build.
- Silosaurs were primarily quadrupeds, using their forelimbs for support rather than propulsion, suggesting they may have been able to run on two legs.
- Ornithischian hips differ from bird hips, with a forward-pointing pubis, unlike the backward-pointing pubis in birds.
- Silosaurs lack features defining ornithischia, like the pre-dentary bone supporting the beak, although their lower jaw resembles a pre-dentary bone.
- Triassic ornithischians shifted from carnivory to herbivory, with basalosaurs being small predators and xylosaurs consuming plants and insects.
- The most dedicated plant eater among silosaurs was kuanasaurus, with diamond-shaped teeth typical of early Jurassic ornithischians.
- Basanasaurus, a derived Triassic ornithischian, was once reassigned between groups, indicating a connection between silosaurs and early Jurassic ornithischians.
- Early ornithischians like Lesothosaurus may have been omnivores, with some evidence suggesting they ate insects and other fauna.
- Early Jurassic ornithischians, like heterodontosaurids, had fang-like tusks for territorial fights, distinct from silosaurs and other basal ornithischians.
- The rise of dinosaurs during the Triassic was opportunistic, taking over niches left vacant by extinctions caused by volcanic activity, leading to their eventual dominance.
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Dinosaurs and Crocodilomorphs Coexisting and Evolving
- Crocodilomorphs coexisted with dinosaurs on land, with some evolving to compete with dinosaurs, such as the large predator Razan Andrew Gobe in the middle Jurassic period.
- Pterosaurs, a type of arcosaurian, diversified during the Jurassic and Cretaceous periods, with some becoming the largest flying creatures and terrestrial animals alongside dinosaurs.
- The age of dinosaurs truly began in the early Jurassic, with sauropods dominating the tropics, theropods evolving to hunt larger prey, and ornithischian dinosaurs like the thyriophoren Skeletosaurus developing bony armor and evolving into quadrupeds.
