This picture shows a selection of theropod dinosaurs from different periods of Earth's history which share the common feature of vestigial or highly reduced forelimbs.

Homologous bones are shown with the same coloration.

Left to right and top to bottom:

- Carnotaurus sastrei - Abelisauridae - Cretaceous;

- Tyrannosarus rex - Tyrannosauridae - Cretaceous;

- Mononykus olecranus - Alvarezsauridae - Cretaceous;h

- Hesperornis regalis - Hesperornithidae - Cretaceous;

- Apteryx australis - Apterygidae - Holocene;

- Raphus cucullatus - Raphidae - Holocene.

Despite bipedalism gives the advantage of having the two left limbs free to evolve for other purposes, such as manipulating things and even flying, we can see how multiple times in dinosaur evolution some critters have "chosen" not to use their arms up to reducing them to little more than stumps.

And despite everyone is laughing at T. rex's little arms, we notice that other dinosaurs have pushed arm reduction even further.

https://www.deviantart.com/thetimeduck/art/Those-who-don-t-hug-their-friends-854269137