Vertebrates minus tetrapods.
This paraphyletic subgroup is easy to form the "acquatic only" (fishes) vs "things that come out of water" (tetrapods). Though mudfish make that distinction harder.
Which kind of makes sense, why would you want for limbs unless you are going to stay out of water!
It is quite mind blowing that this is polyphyletic on mammals and birds, what can't parallel evolution achieve??
- prokaryote models:
- E. Coli: the most well studied
- mycoplasma: a very minimal genus, notable species: Mycoplasma genitalium
- eukaryote
- S. cerevisiae: simplest eukaryote model. Unicellular.
- C. elegans: simplest multicellular organism model
- vertebrate:
- Zebrafish: simplest vertebrate model
- mammal:
- Mus musculus: simplest mammal model