Dinosaurs were made up by Richard Owen? ?

They did but not in the form they are presented, the Earth was very much different back then, much wetter, higher pressure atmosphere and most land was under water, there were vast shallows that the "dino's" occupied.

The "dino's" were alligator like, bird like, fish like.

My paper about this: vixra.org/pdf/2007.0072v2.pdf

Regards,
Daniel

Jeffrey has some dino papers too:
Dinosaurs Could Submerge Themselves and Breathe While Walking in Shallow Lakes, Their Long Necks Really Did Function as Snorkels
Expanding Earth, Semi-Aquatic Dinosaurs, Earth Atmosphere in 3-5 Bar, Exoplanets and Stellar Metamorphosis

I also made an attempt to show how the evolution from a Neptune like world to an Earth like world happens:
vixra.org/pdf/1801.0149v1.pdf

If T-Rex lived in lakes, it might explain the tiny forearms.

Nah. Many or most dinosaurs died on highlands, like "Dinosaur Peninsula" dl0.creation.com/articles/p117/c11779/fig-3-lge.jpg -- creation.com/geological-perspective-on-floating-forests from Minnesota and Michigan to Idaho and New Mexico.
I made a post 4 days ago about that time at cataclysmicearthhistory.substack.com/p/from-preflood-to-postflood-world . The dinosaurs were almost all wiped out by the Great Flood as they were fleeing to escape, so the younger ones were overcome before the adults, so adults and young were often not found together. Asteroid collisions and/or planetary tidal forces caused tidal waves or tsunamis that got progressively higher and deposited almost all of the sedimentary rock strata on the continents, when they were part of the Pangaea supercontinent, about 5,300 years ago, before mountains formed from the Pangaea breakup.