To what point of the Palaeozoic epoch, then, must we, upon any rational estimate, relegate the origin of the monotremata?
"Critiques and Addresses"
Thomas Henry Huxley
In the earliest stage represented by the monotremata or Prototheria, there was no intra-uterine development.
"Hormones and Heredity"
J. T. Cunningham
Three families-1st, Tardigrades, the Sloths, peculiar to America; 2nd, Effodientia, or Burrowers, of which the Indian type is the Manis, but which includes in other parts of the world the Armadillos and Anteaters; 3rd, monotremata, Spiny Anteaters or Echidnas, and the Ornithorynchus.
"Natural History of the Mammalia of India and Ceylon"
Robert A. Sterndale