Modern birds share many similarities with theropod dinosaurs, which are a group of bipedal carnivorous dinosaurs that included Tyrannosaurus rex, Velociraptor, and many others. Here are a few similarities:
1. Feathered bodies: Many theropod dinosaurs had feathers, and modern birds are direct descendants of feathered theropods. This means that birds still have feathers, despite evolving in many different ways.
2. Hollow bones: Like theropod dinosaurs, birds have hollow bones that are filled with air sacs. This makes their skeletons lighter and helps them to fly more easily.
3. Similar skull structure: The skulls of certain theropod dinosaurs and birds have a similar overall structure, with a toothless beak at the front and a large braincase at the back.
4. Warm-bloodedness: Some scientists believe that theropod dinosaurs were warm-blooded, like modern birds. This would have allowed them to survive in a wider range of climates and environments.
Overall, the similarities between modern birds and theropod dinosaurs suggest that birds are closely related to these ancient reptiles, and that they share many common traits and adaptations.