General characters and affinities of dipnoi?

Dipnoi, also known as lungfish, are a group of freshwater fish that are characterized by their ability to breathe air. They have a unique respiratory system that allows them to extract oxygen from the air, in addition to gills for breathing underwater.

Some general characteristics of dipnoi include:
1. Elongated bodies with paired fins
2. A single dorsal fin
3. A toothed mouth for feeding on small invertebrates and plants
4. A primitive lung that allows them to breathe air

In terms of affinities, dipnoi are considered to be a primitive group of fish that share some characteristics with both bony fish and tetrapods (four-limbed vertebrates). They are often considered to be a transitional group between fish and amphibians, as they exhibit some features of both groups. Dipnoi are also known for their ability to aestivate, or enter a state of dormancy during dry periods, which is a unique adaptation among fish.