Define monotreme. Monotremes are unique because their urinary, excretory, and reproductive systems share the same opening (monotreme means 'single opening' in Greek). Early monotreme fossils have been found in Australia. Marsupials are named after the pouch, or marsupium, in which their young spend most of their foetal development. Molecular Biology and Evolution 19(12):2060-2070. Nature 446(7133):288-293. C) The domain Archaea is known to be the first branch, domains Bacterica and Eukarya are more closely related to each other. ... Moosmosis: Evolutionary Tree and Phylogeny of Reptiles, Platypuses, and Eutherians . A. Hopson, A. M. Musser, T. F. Flannery, and P. Vickers-Rich.

Simplified morphology-derived placental tree, based mostly on one of the strict consensus trees shown by Novacek (1992a) (and with some of the names coming from McKenna & Bell 1997). Rich, T. H., J. 2005. The first monotremes may have evolved about 150 million years ago. This chapter provides an evolutionary context to comparative research on monotremes and marsupials.

Phylogenetic parsimony analyses, in which selected mammalian lysozymes were used as outgroups, yielded trees whose consensus indicated that the two monotremes are sister taxa to marsupials and eutherians and that the latter two clades are each other's closest relatives. Placental mammals comprise three principal clades: Afrotheria (e.g., elephants and tenrecs), Xenarthra (e.g., armadillos and sloths), and Boreoeutheria (all other placental mammals), the relationships among which are the subject of controversy and a touchstone for debate on the limits of phylogenetic inference. Mi-Hye Lee, Robert Shroff, Steven J.B. Cooper, Rory Hope, Evolution and Molecular Characterization of a β-Globin Gene from the Australian Echidna Tachyglossus aculeatus (Monotremata), Molecular Phylogenetics and Evolution, 10.1006/mpev.1999.0610, 12, 2, (205-214), (1999). Monotremes are mammals that lay eggs instead of giving birth, and currently, the platypus is one of the five existing montrome species. The order Monotremata is the only extant group within the subclass Prototheria - the oldest living taxon of theclass Mammalia.

Luo, Z. X., P. J. Chen, G. Li, and M. Chen. J. Biochem.218, 457-461 (1993) 0 FEBS 1993 Evolution of the monotremes The sequences of the protamine P1 genes of platypus and echidna Jacques D. RETIEF, Robert J. WINKFEIN and Gordon H. DIXON Department of Medical Biochemistry, University Calgary, Health Sciences Center, Canada (Received June 14/September 7, 1993) - EJB 93 0888/1 The protamine PI genes from two monotremes…