Monotremes

A truly bizarre and unique assortment of animals, including marsupials (kangaroo and koala bear) and monotremes (platypus and echidna), have carved niches for themselves in its barren earth. ❋ Rick Springfield (2010)

A more solid answer would emerge if, for instance, the molecular networks behind the formation of the appendix in monotremes and humans were compared, and found to use the same toolkit of genes — then we'd have to regard it as highly probable that they are homologous, and the last common ancestor had an appendix. ❋ Unknown (2009)

That's interesting: the only groups that have an appendix are the Glires rodents and rabbits, primates, monotremes, and some marsupials. ❋ Unknown (2009)

The platypus is one of only three monotremes - egg-laying mammals - in the world. ❋ Unknown (2007)

The mammal fauna includes 2 monotremes, 37 marsupials, 16 rodents and 34 bats. ❋ Unknown (2008)

Just so everyone knows, they are definately _not_ monotremes or therian mammals. ❋ Darren Naish (2006)

To the examples Tommy listed I would add monotremes. ❋ Darren Naish (2006)

These include two species of monotremes, 32 marsupial species, 31 bat species and 10 species of rodent. ❋ Unknown (2008)

When the lineage that gave rise to the modern monotremes split from the lineage that gave rise to marsupials+placentals, this was very likely just another routine speciation event. ❋ Unknown (2007)

Bradford seems to think that modern evolutionary theory says that there “should” be some obvious event like the K-T impact to explain “major” events like the divergence of monotremes and marsupials+placentals, the divergence of marsupials from placentals, the divergence of the mammalian orders, the divergence of the mammalian families, etc. ❋ Unknown (2007)

But these fossils, even though they are from the true ancestral species of monotremes and marsupials+placentals, probably would not have any major distinguishing derived characters that would allow you to place either species specifically in the monotreme or marsupial/placental branch. ❋ Unknown (2007)

Since monotremes are egg-layers I wonder how, if they produce urea, they manage to not poison their developing young. ❋ Unknown (2006)

Scratch that last comment: Fruitafossor was actually a true mammal, nested between monotremes and their extinct kin on one branch, and triconodonts, multis, marsupials, and placentals on the other. ❋ Unknown (2006)

What form does nitrogenous waste excretion take in monotremes? ❋ Unknown (2006)

Well, monotremes make milk but don't have nipples. ❋ Unknown (2006)

Oviparous reproduction makes monotremes the ideal emblem of sudden, unexpected, and heartbreaking failure. ❋ Unknown (2006)

And the monotremes got a different hand where it got egg laying and venom production plus warm blood. ❋ Unknown (2006)

[The platypus] and the [echidna] are the only known monotremes that [exist] in the world. ❋ Nordicdragon (2018)

"Dude, is a total monotreme he can't run or [move] right and has [a funny] [body]." ❋ Grudog (2020)