So yes, the Echidna (Tachyglossus aculeatus). Echidnas are monotremes. What is a monotreme, you ask? A monotreme is an egg-laying mammal. Your first thoughts may jump to the duck-billed platypus, and you would be correct. These are the only two species of this order left alive today. The characteristics that they share originated in ancient mammals, which all other mammals evolved away from. Not only do these mammals lay eggs, they also have primitive skeletal features including the shoulder girdle and skull characteristics.
The echidna is also known as the spiny anteater and it is found in Australia, Tasmania, and New Guinea. They look similar to hedgehogs but are, in fact, not at all related. Their spines are actually modified hairs and the body is insulated by fur between the spines.
Echidnas are adapted for digging and spend most of their time searching for food, including ants and termites. The adapted claws are used to break open the termite mound or ant hill and the snout and super long tongue are used to search for the food.
Echidnas also exhibit a pretty unique reproductive system. They possess a cloaca, not unique, which is a common opening for reproductive, urinary, and digestive tracts. The unique aspect comes with the echidna's penis.
After fertilization, the female lays a single egg into her stomach pouch. The baby is born after only 10 days. It remains in the pouch, feeding off of mammary secretions through the skin (echidnas possess neither teats nor nipples). When the young is covered with spines and fur it then leaves the pouch for a life on it's own. Up to 45 years of life in the wild.