It's #WorldCrocDay! I don't talk about it much on here 'cause...I'm honestly still not over the trauma grad school caused...but I study alligatorines (everything closer to American #Alligators than to Spectacled Caimans). And I'm gonna talk a bit about 'em today.

There are two species alive today: Chinese (left) and American (right)
Photo by @UglyFossils
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But there were a couple dozen more (that we know of) over the course of their ~66 million year-long existence.

Figure from Brochu (2004). The first two are just outside Alligatoridae (alligatorines+caimans), but the rest are alligatorines.
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American #alligators are really weird gators. Like Brochu's figure shows, most of them have short snouts. They're also almost all small (~5-6 ft as adults) and have bulbous back teeth.

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This type of tooth is an adaptation for durophagy, crushing and eating hard things . Wild Savannah Monitors (top center) eat crunchy arthropods and snails. Placodonts (top right) probably ate molluscs.

Top 3 images not mine
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Most extinct alligatorines lived alongside large, generalist crocodyloids (things closer to crocodiles than gators). What's a species to do when it can't beat its competitor? Find a different niche.
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By moving from the large generalist niche of their ancestors to a small durophagy-specialized one, they were able to coexist.
When the climate cooled and the heat-loving crocs were extirpated, the surviving gators began the shift back to being large generalists.
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Mind you, the extant American Alligator still loves crunchy things like turtles. But the small extinct ones wouldn't have predated any this big—they would've been left for the larger crocs.
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And that's how #alligators show that specialization is not an evolutionary dead end. It's possible for specialists to evolve into generalists, contrary to what you're normally taught in #ecology. All it takes is opportunity.
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Also that, no, they haven't stayed the same for millions of years, so stop calling them "living fossils". Just go ahead and strike that phrase from your lexicon entirely.
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Now go follow the hashtag to hear more about the amazing, diverse history of crocodylians and their extinct relatives from a whole host of croc researchers!
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