Spinoaequalis schultzei, an early diapsid reptile from the late Carboniferous of Kansas, USA (~300 mya). Measuring about 30cm long (1′), it appears to have been semi-aquatic, with limbs like a typical terrestrial reptile but also possessing a long flexible paddle-like tail to aid in swimming – making it one of the earliest amniotes to experiment with “returning to the water”.
Spinoaequalis
![A stylized illustration of an an extinct semi-aquatic reptile, depicted basking on a fallen tree branch. It resembles a lizard with a long paddle-like tail.](https://nixillustration.com/wp-content/uploads/2017/02/spinoaequalis.png)