In the first episode of this series, Cats, I asked if it's possible for all 600 million house cats to evolve different niches if they were the only amniotes in a terraformed world. Needless to say, it's going to be a blue moon kind of extremely difficult because the cats' specialties in eating meat are that extreme.
So scratch the kitties. Instead, let's look to a terraformed world full of a different group of amniotes: Crocodilians. There are two separate criteria for this question.
- It must be from a species that we humans have bred captively for non-zoo purposes.
- It must be from a species that is listed in the wild either as Least Concern or Near Threatened.
These two criteria have reduced an already small list into this even smaller list:
- American alligator
- Nile crocodile
- Morelet's crocodile
- Freshwater crocodile
- Saltwater crocodile
- New Guinea crocodile
Long ago, different branches of crocodylomorphs had occupied the niches that would later be filled by their competitors, the dinosaurs. Creatures like bipedal Effigia and Postosuchus, sail-backed Arizonasaurus and toothless Shuvosaurus ruled the world during the Trassic period only to disappear during the extinction event at the beginning of the Jurassic period, 201 million years ago. In their absence, the previously established dinosaurs could now claim the world as their empire for the next 135 million years, taking on a wide variety of shapes, sizes and niches as a result.
Now, the crocodilians listed above have no relation to the Triassic crocs who looked and acted like dinosaurs, but in a terraformed world where there are no other amniotes (there are still fish and amphibians around, as these reptiles can tackle a wide variety of prey items), would they have evolved and diversified into the terraformed world's "neo-dinosaurs"?