On this parallel earth all vertebrates received the ability to efficiently produce super strong materials from readily available minerals/nutrients in the mid Triassic.
The specifics of these composite organic metamaterials aren't super important just that:
- The metamaterials are of comparable density to bone, but with over 60 times the compressive strength of even the strongest bone and vastly more tensile and shear strength. This also makes these materials stronger than anything humans can currently synthesize in large quantities, by a fair margin.
- The metamaterials can be up to as hard as diamond.
Let's also assume that when creatures received this ability, they very rapidly developed the ability to produce these composite materials in as many different ways as as they can produce bone and keratin (to ensure they actually fully utilize the potential of these materials).
When it comes to the super strength aspect of this question, assume the autotrophs at the base of food chain started producing over an order of magnitude more caloric energy in the mid Triassic as well. Additionally these autotrophs and the animals that eat them have developed new stores of chemical energy that can function as well as fats and carbohydrates, but have energy densities on par with natural gas.
Given many dinosaurs in evolutionary history seem to have reached about the maximum size that their biology allowed, this seems like an area where one should be able to make quite decent predictions about speculative evolution.
The mid Triassic is being chosen as the starting point for this speculative evolution question, because dinosaurs were already widespread.
So with these advantages how large and fearsome would dinosaurs become?
Answers should take into consideration that other than the specific traits mentioned above, these creatures are still evolving from actual dinosaurs. With their initial biology varying only in the aforementioned ways.