what is the third one?
A hedgehog is any of the spiny mammals Their spiny protection resembles that of the unrelated porcupines, which are rodents, and echidnas, a type of monotreme.
Hedgehog
A hedgehog is any of the spiny mammals of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found through parts of Europe, Asia, and Africa, and in New Zealand by introduction. There are no hedgehogs native to Australia and no living species native to the Americas (the extinct genus "Amphechinus" was once present in North America).

Hedgehogs share distant ancestry with shrews (family Soricidae), with gymnures possibly being the intermediate link, and they have changed little over the last 15 million years. Like many of the first mammals, they have adapted to a nocturnal way of life. Their spiny protection resembles that of the unrelated porcupines, which are rodents, and echidnas, a type of monotreme.
mammals are the only group of animals to demonstrate significant protection of their young UNANSWERABLE what is this particular group of animals? The Belon the placental group. do they have hairs on their body? Yes. The earliest evidence suggesting this is from 164 Million Years ago can you name a few examples of this group of animals? Rodents, Bats, Hedgehogs, Monkeys & Humans among many others
wiki:11628390
Hedgehog [SEP] Introduction
A hedgehog is any of the spiny mammals of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found through parts of Europe, Asia, and Africa, and in New Zealand by introduction. There are no hedgehogs native to Australia and no living species native to the Americas (the extinct genus "Amphechinus" was once present in North America). Hedgehogs share distant ancestry with shrews (family Soricidae), with gymnures possibly being the intermediate link, and they have changed little over the last 15 million years. Like many of the first mammals, they have adapted to a nocturnal way of life.