Recent Acquisitions

[Monkeysaurus]

@Faelrin

Thanks for all that info! I know that the transition from "reptile" (yes I know it's
not a real category) to mammal took an insanely long time. Like 100 million years or so. I've always wanted to find out where
the earliest signs of proto-nursing developed. I imagine it would've started out like modern day platypus - sweating some sort of nutrient that the babies lap up. It's our defining trait and it would be a dream to have well preserved evolutionary gradients like we do with whales and early Homo. I actually think about this often. I believe the earliest known unarguable mammal as we know them was late Triassic so nursing would've evolved before then some time.

[Faelrin]

@Monkeysaurus Reptilia is valid. The groups typically defined as reptiles fall under the clade Sauropsida. However animals like Estemmenosuchus, Lystrosaurus, Inostrancevia, Dimetrodon, and mammals all fall under the clade Synapsida. Both sauropsids and synapsids are amniote (egg laying) tetrapods. Mammal-like reptile was historically used for non mammal synapsids, but has become antiquated for some time now, as synapsids aren't considered to be reptiles any longer with the current phylogenetic understanding.

This section on the wikipedia article on Synapsida has more information regarding integument from non mammal synapsids:

https://en.wikipedia.org/wiki/Synapsida#Skin_and_fur

It seems something like used in monotremes for milk production (or some nutrient rich substance) would have been present as far back as Cynodontia (a non mammal therapsid clade, but which mammals have evolved from). Hair has been found as far back as the Permian.

These other articles might be of interest as well:
https://en.wikipedia.org/wiki/Mammaliaformes
https://en.wikipedia.org/wiki/Evolution_of_mammals

[Monkeysaurus]

I'm not a fan of the term reptile, because it doesn't reflect actual relation in the same way mammal or bird does. For the term to still work you would have to include birds essentially. I'm also pretty sure including turtles in the group causes issues as well. The traits defined as reptilian are more due to convergent evolution rather than relation. Sauropsida is perfectly fine to me , as is squamate for lizards and snakes and archosaur for dinos and crocs. Mammal works both in common and scientific sense.

None of this really matters though in the grand scheme of things I suppose. Nature doesn't care about our labels so as long as you can read the music and understand the reality of the thing in question. That aside that is fascinating that "nursing" may actually be that old! Sweating nutrients I mean. I guess from there it's just a matter of those pores becoming more "nipply" and the "sweat" becoming more milky. Thank you for the links