monotremes

A popular pub-trivia question is how many types of (living) monotremes are there - two (echidna and platypus).

But all surviving monotremes live in and around the water, in places where they mostly compete with marsupials.

When mammals diverged further, monotremes lost one of the blue receptors while other mammals lost the other.

Isn't it possible to compare dna between marsupials, mammals and monotremes and figure out which is 'earlier'?

It's not clear whether they are like marsupials or whether they laid eggs like monotremes.

Marsupials and placentals are more closely related than any of them is related to monotremes.

This works until the analogue of monotremes shows up to ruin your supposedly flawless categorisation.

Clearly monotremes are similar to other mammals in many respects but very different in others.

Echidnas and the platypus are the only egg-laying mammals, known as monotremes.

The surviving monotremes are the platypus and several species of echidna.

> the mammalian talent for live birth Monotremes are egg-laying mammals so the author is identifying with placental and/or marsupial mammals, and not mammals as a whole.

And a million other questions that monotremes stir within me.

And monotremes like the platypus, an animal that lays eggs but nurses its young with milk." Former biologist here.

OO simulates the real world!"), somebody had the foresight to ask how things like monotremes are represented.

A title such as "Monotremes: Weirdo Australian animals" might be a little better.

For example, let’s say you’re trying to classify animals into groups and you’ve “been trained” on a dataset that doesn’t include monotremes or marsupials.

Monotremes are rather obviously a very early mammalian offshoot, having retained significant original character (and a lot of weirdnesses) compared to therians.

Monotremes don't have the SRY gene but do have males and females.

Monotremes (and marsupials) have fascinated me since I was a kid.