Monotremata. There are only five living monotreme species: the duck-billed platypus and four species of echidna (also known as spiny anteaters).
All of them are found only in Australia and New Guinea. Monotremes are not a very diverse group today, and there has not been much fossil information known until rather recently. In some ways, monotremes are very primitive for mammals because, like reptiles and birds, they lay eggs rather than having live birth. In a number of other respects, monotremes are rather derived, having highly modified snouts or beaks, and modern adult monotremes have no teeth.
Science - Interact Simulations. Disorders of Carbohydrate Metabolism: Hereditary Metabolic Disorders. Duchenne muscular dystrophy and Becker muscular dystrophy cause weakness in the muscles closest to the torso. These dystrophies are the most common muscular dystrophies and nearly always occur in boys. On average, 1 of 3,000 boys born has Duchenne muscular dystrophy, whereas on average 1 of 30,000 boys born has Becker muscular dystrophy. The gene defect that causes Duchenne muscular dystrophy is different from the gene defect that causes Becker muscular dystrophy, but both defects involve the same gene.