they are the ones that get energy from outside sources right?

An ectotherm is an animal in which the internal body temperature is the same as the temperature of its surroundings. Fish, amphibians, and reptiles are ectotherms. Ectotherms can not control their internal body temperature and therefore have to stay in either the sun to stay warm, or the shade to keep cool.

http://vilenski.org/science/safari/clas … oecto.html

There are several ways.

Most of them involve behavioral responses – moving to warmer / cooler areas, or settling in stable places, like burrows.

Many ectotherms can generate heat metabolically, often through muscle activity.

On top of that, many ectotherms have more than one efficient temperature range that they can be active in.

Alternatively, consider ancient Mammal-like reptiles – Dimetrodon and many Edaphasaurids had sails on their backs formed from elongated neural arches.

Do any extant species have this adaptation?

I’ve read that sauropods might have maintained some level of body temp because of their huge mass. The more dense a body is – the less heat escapes.

I was trying to think of any extant species that have large neural arches the other day. I couldn’t come up with anything other than sailfish & I have no idea what they use theirs for.