The Main Architects of Evolution: Theropods—The Most Successful Hunters in History and the Lineage That Evolved into Birds.
Theropods are a group of dinosaurs belonging to the order Saurischia, characterized by lizard-like pelvises, and are known primarily for being carnivorous.
They are one of the three major dinosaur groups, flourishing across vast regions of the Earth from the Late Triassic, approximately 230 million years ago, to the Late Cretaceous, making them one of the most successful species in history.
Physical Characteristics of the Hunters That Reigned at the Apex of the Dinosaur World
Theropods reigned as apex predators in Earth’s ecosystems from the Jurassic to the Cretaceous.
Their strength and success were based on their unique physical structure.
1. Swift Bipedalism and Powerful Hind Legs
Theropods are characterized by slender bodies and long hind legs, with all species walking on two legs.
Their leg muscles were extremely developed, and many species were capable of running at speeds of over 30 km/h, making them adept at quick movements.
They excelled at quick movements
This agility was a major key in tracking down prey.
2. Powerful Heads and Skeletal Secrets
As seen in representative theropods like Tyrannosaurus and Giganotosaurus, they were armed with massive heads and rows of extremely sharp teeth inside their mouths for tearing apart prey.
Armed with rows of sharp teeth inside their mouths
They also possessed hollow bones that lightened their skeletons. This feature, which enabled their agile movements, was a significant evolutionary secret inherited by later birds.
Evolution and Diversity: Changes in Diet and Development of Intelligence
Theropods were not just giant predators; they underwent surprisingly diverse evolution and expanded their ecological niches.
1. Adaptation to Diverse Diets
Initially, theropods were carnivorous, producing numerous predators that stood at the top of the ecosystem, such as Allosaurus.
However, dietary diversity emerged during their evolution.
By the Cretaceous period, it has been confirmed that herbivorous dinosaurs like Jianchangosaurus had appeared.
By possessing diverse diets, like Oviraptor and Therizinosaurus, they adapted to different environments.
2. Intelligence and Sociality
Intelligence developed in theropods, centering on the lineage that became ancestors to birds.
In particular, the group to which Velociraptor belongs is considered to have had superior brainpower, and it is known that some dinosaurs exhibited social behaviors, such as forming packs to hunt.
Some dinosaurs formed packs to hunt
Evolution into Birds: Pioneers of Feathers
Theropods diversified dramatically by the Late Jurassic, and birds emerged from this evolutionary lineage.
Acquisition of Feathers and Evidence of Evolution
Theropods are also known as the first group of dinosaurs to acquire feathers.
The “Paravians” (or stem-birds), to which Deinonychus and Velociraptor belong, are considered the direct ancestors of modern birds.
The inclusion of early birds like Archaeopteryx also indicates that theropods followed the lineage of birds.
Archaeopteryx
Birds inherited theropod characteristics, such as bipedalism and hollow bones, and having survived the mass extinction at the end of the Cretaceous, they continue to thrive today.
Major Classification Groups and Discoveries in Japan
Theropods are divided into numerous subgroups, including Ceratosaurs, Tetanurans, Coelurosaurs, and Coelophysis-like dinosaurs.
The ultimate descendants of these groups are the birds living today.
Theropod fossils have also been discovered in Japan. In 2013, fossils believed to be from a theropod dating back approximately 85 million years were found in strata in Kuji City, Iwate Prefecture, attracting attention as the first such discovery in the Tohoku region.
Theropods are one of the most successful groups among dinosaurs, and their evolutionary history teaches us about the adaptability of life on Earth and its magnificent evolutionary journey.
