Some dinosaurs did have spines but most did not. The main body coverings of most dinosaurs were scales and feathers.
because we find their bones and we can see that they have spines
Hedgehog
No. The platypus is covered with dense, waterproof fur, and the echidna is covered with sharp spines.
The echidna is an egg-laying mammal. It is a beak-like snout, and its body is covered with spines.
Pufferfish
The Echinoderm's body is covered in spikes/spines.Some spines/spikes are long, and some are short.
An echidna's body is covered with spikes, or spines. These spines are not poisonous, but they are sharp and offer the echidna protection from predators.
The echidna is an animal which lays eggs. The echidna is covered in spines. Like platypuses, echidnas are monotremes, or egg-laying mammals.
A sea urchin's body is covered in sharp spines.
Sea urchins are covered almost entirely with spines, except for the bottom of their body.
Monotremes are covered with skin, but over the skin they have fur. Both platypuses and echidnas have fur, and echidnas also has sharp spines.
It's a sea urchin.