Paleo Profile: The Whale Caiman

Apr 10, 2017

By Brian Switek

Crocodylians are deceptive. I’m not just talking about their skill as aquatic ambush predators, concealed until the moment they’re a blur of teeth and scales. Rather, the existing species of alligators, crocodiles, and gharials have often been incorrectly characterized as “living fossils” that have changed little since the Mesozoic. The fossil record readily dispels this notion, proving that crocodylians were even more varied in the past. With that in mind, Mourasuchus is a wonderful example of the greater crocodylian variety that once existed on our planet.

This weird caiman was first described in 1964 under the name Mourasuchus amazonensis. A handful of other species have been recognized since then, with the latest being Mourasuchus pattersoni named just this year by paleontologist Giovanne Cidade and colleagues from the Miocene strata of Venezuela. It’s odd for a caiman. This was not a short-snouted little nipper, like the black caimans you’ve likely seen on natural history documentaries, but a long-faced crocodylian that looks like it’s trying to do an impression of a baleen whale.

Such a strange skull is a sure sign Mourasuchus was doing something different than its modern relatives. But what? The long, wide snout with small teeth indicate that this caiman probably eschewed large, struggling prey for smaller fare. Following from this hypothesis, Cidade and coauthors suggest Mourasuchus a “gulp feeder” – a caiman that captured various small mollusks, crustaceans, and small fish en masse with its broad jaws. This wasn’t filter feeding, the authors caution, as the caiman had no mechanism to separate sediment or plants from protein, but rather a uniquely crocodylian way of snaffling up little morsels in great quantities.

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