The closest animal to a dinosaur is the bird. Birds are considered the modern-day descendants of theropod dinosaurs, specifically the group that includes species like the Tyrannosaurus rex and Velociraptor. This connection is supported by numerous fossil discoveries, which show that many characteristics we associate with birds today, such as feathers and hollow bones, were present in some dinosaurs.
Scientists have gathered substantial evidence pointing to the evolutionary link between birds and dinosaurs. For instance, fossils of the Archaeopteryx, which lived about 150 million years ago, display features of both theropod dinosaurs and modern birds, including feathers, wings, and a skeletal structure similar to that of small raptors.
Additionally, genetic studies and comparative anatomy have demonstrated that birds share a high degree of genetic material with their dinosaur ancestors. This evolutionary relationship has led to the understanding that when we look at birds today, we are essentially observing living dinosaurs, adapting and thriving in a world vastly different from their prehistoric origins.