Hi! (not sure it's in the right category...).
I've read about Neoteny and it's supposed role in evolution. somewhere, I've read the the opposite of it is called Hypermorphism, which means over-evolving of a structure, like the horn of a Rhino, or the human breast.
but I can't find this source anymore, and therefore suspect I misunderstood. is there such a thing (Hypermorphism or something else as opposite to Neoteny) and where can I read about it or find examples to it?
Thanks, it's a great service you give!

Hypermorphism in genetic terms is an activating mutation in a single gene that phenotypically is a gain-of-function ie the protein made by the gene is more active. As you can see that has nothing really to do with neoteny and is certainly not its opposite.

The wiki page on Neoteny is I think rather good!