The Triassic/Jurassic extinction paved the way for non-avian dinosaurs to become the dominant vertebrates for the rest of the Mesozoic. However, there were many other vertebrates around at this time Which of these is a possible reason that non-avian dinosaurs were so successful?

a. The late Devonian extinction left many ecological niches open for non-avian dinosaurs to fill

b. Non-avian dinosaurs produce eggs with hard shells which provides protection against desiccation

c. Non-avian dinosaurs were al small and so didn' t require much vegetation to survive

d. The possession of feathers by both major clades of non-avian dinosaurs allowed them to survive the swings in temperature seen through the Mesozoic

e. The evolution of a bi-directional tidal breathing respiratory mechanism allowed them to outcompete other groups of vertebrates.

d. The possession of feathers by both major clades of non-avian dinosaurs allowed them to survive the swings in temperature seen through the Mesozoic

Explanation:

The possession of feathers provided dinosaurs with a major advantage: mesothermy. This kind of metabolism is a transition form between cold - (ectothermy) and warm-blooded (endotherm), increasing their adaptation capabilities as the climate changed. The Mesozoic saw the breaking up of Pangaea first into two landmasses (Laurasia and Gondwana) and more individual landmasses towards the end.

a. The late Devonian extinction left many ecological niches open for non-avian dinosaurs to fill.

This cannot be the right answer since the Devonian extinction did not occur during the Mesozoic. The Permo-Triassic extinction did open many ecological niches, but these were exploited by all ornithodirans (meaning crocodiles, dinosaurs, and pterosaurs).

b. Non-avian dinosaurs produce eggs with hard shells which provides protection against desiccation

This is an advantage that relates to the success of amniotes (all vertebrates except for amphibians), and it played an important role in vertebrate evolution during the Late Devonian.

c. Non-avian dinosaurs were al small and so didn' t require much vegetation to survive.

Dinosaurs occupied several size scales, from very small to the most gigantic forms. Additionally, not all of them were herbivores. Although herbivory evolved independently in dinosaurs at least three times (Sauropodomorpha, Thyreophora, Neornithischia), the first dinosaurs were carnivores.

e. The evolution of a bi-directional tidal breathing respiratory mechanism allowed them to outcompete other groups of vertebrates.

This respiratory mechanism evolved at the beginnings of reptile evolution (as early as the Pensylvannian in the Carboniferous). It consists of having two influxes (exhalation and inhalation) of air into the lungs through the same channel. Fish, for instance, have an unidirectional breathing respiratory mechanism were the water enters through the mouth and leaves through the gills, were the oxygen is filtered. Dinosaurs already inherited this breathing mechanism.