They lay eggs and are the only animals with feathers. Birds also have a light skeleton, with hollow bones that make it easier for them to fly. Like mammals, birds come in all sizes and shapes ...

(Both are named after their relative shapes.) Cones work in bright light ... (Interestingly, different animals have different color tapeta, a fact that can aid in nighttime animal identification.) ...

Dozens of different studies using everything from ... the animals that lived during the Ediacaran were mostly soft-bodied, blob-shaped animals like cnidarians — a group that includes animals ...