Evolution of Dinosaurs into Birds
Introduction:
- In his acclaimed 1859 book On the Origin of Species, British naturalist Charles Darwin first proposed the theory that life forms evolved through natural selection. Thomas Henry Huxley, an anatomist, argued that present birds could be related to prehistoric dinosaurs.
Dinosaur morphology:
- The evolution of dinosaur skulls into bird skulls has long been a focus of research in the field of dinosaur palaeontology.
- By focusing on the nose, this study expanded our understanding of how the cranium evolved from dinosaurs to birds.
- Two fossils discovered in China in 1998 provided paleontological evidence of theropod dinosaurs and modern birds’ kinship.
- The dinosaurs gradually developed birdlike characteristics like wings and wishbones.
- Scientists are still unsure as to whether dinosaurs had warm or cold blood.
- Because lizards are ectotherms, the word “dinosaur” comes from the Greek words “deinos” and “sauros,” which mean “terrible lizard.”
- On the other hand, dinosaurs and warm-blooded birds have a common ancestor.
- The complex nasal or respiratory turbinate, which resembles a scroll and is made of thin bone plates, is seen in warm-blooded species.
- There are no cold-blooded creatures without nasal turbinates. They are in charge of managing the heat and moisture exchange that occurs during breathing.
- Due to their fluid nature, nasal turbinates seldom ever survive fossilisation.
- 51 living species, including 11 Lepidosauria (snakes, lizards, iguanas, etc.), 4 Crocodylia (crocodiles and alligators), 8 mammals, 21 birds, and 3 Testudines (turtles and tortoises), were imaged using computed tomography (CT). The scan data was then used to create a 3D reconstruction of their nasal cavities.
- The researchers also digitally reproduced the three-dimensional nasal cavity of a theropod known as a velociraptor based on relics.
- Comparing these 3D scans to the size of the animals’ skulls, the researchers found that warm-blooded animals had nasal chambers that were much larger than those of cold-blooded species.
Various types of dinosaurs:
- The reconstruction and other research also shed light on the respiratory turbinates’ lesser-known physiological function of cooling the brain.
- The study discovered that one of the primary functions of the respiratory turbinate and the larger nasal cavity is cooling the larger brains of [warm-blooded animals], not whole-body metabolism.
- Theropods lacked a fully developed cooling system, which would be required for a brain to “operate” a warm-blooded creature, and the velociraptor’s nasal cavity was smaller than modern birds’.
- Mammals and birds, on the other hand, had large nasal cavities that could accommodate a developed respiratory turbinate, which in turn successfully cooled their brains.
- Additionally, they found that the shape of the velociraptor’s nasal tube was significantly influenced by the maxilla.
- Based on this, they have proposed that a major reduction in the maxilla in the theropod phylum caused the nasal cavity to become an essential part of their heat regulation strategy.
Conclusion:
Adapting to their environment is how organisms evolve, as opposed to evolving in a vacuum. A full understanding of the development of dinosaurs and the environment of the planet they lived on will be necessary to comprehend the lineages that led to each phylum or class in the Animal kingdom.
