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South American caiman ancestor gulped its prey like a pelican

Modern crocodiles and their ancestors, the crocodyliforms, have a weird and wonderful evolutionary history. If you look back in time through the fossil record, we see that we have a huge diversity of species with peculiar forms. This includes giant sea-swimming species, armoured armadillo-like ones, and even some which were more boar-like and herbivorous.

One of these now extinct crocodyliforms, known as Mourasuchus, had an unusually wide and flat snout, sort of like an elongated pancake. Its mandibles were very long and slender, not like the strong and robust jaws we see in most modern predatory crocodiles.

The skull of Mourasuchus pattersoni (Cidade et al., 2017)

Mourasuchus is part of a group called Caimaninae, which includes the modern caiman, and are found mostly in South America – both the fossils and the living species. In a recent study, a team of researchers from Brazil and Venezuela identified a new species of this animal, named Mourasuchus pattersoni. This joins the other three named species of this genus, all also known from the Miocene (5-23 million years ago) of South America.

Vital statistics

Country: Venezuela

Location: NE of the town Urumaco, Falcón state, Venezuela

Age: ~6 million years old

Rocks: Urumaco Formation

Giovanne Mendes, lead author of the study, explained “Well, it is a cool finding by itself, but the history itself is also interesting. The specimens were collected in 1972 in Venezuela, and then went to Harvard where it underwent restoration. It returned to Venezuela in 2002, and only came to be described now in 2017.”

Please note any unusual dietary preferences

The sheer size of Mourasuchus, as well as its wide, flat skull, suggests that it had a very unusual diet. Mendes and team even refer to the poor animal as “duck faced” in their article! Maybe that’s where humans picked it up from after all then… The long, slim jaws and relatively small teeth would have been unable to capture and dismember large prey, like we see in modern crocodiles. So just what was Mourasuchus doing?

The slender mandibles of Mourasuchus pattersoni (Cidade et al., 2017)

Mendes said “We explored the feeding habits of Mourasuchus, a very different taxon from other crocodylians. What we suggest is that they performed ‘gulp-feeding’ on large amounts of small animals such as molluscs and crustaceans.”

This is the sort of thing having a large mouth area is really great for, just like we see in modern filter-feeding whales too. Mourasuchus would have scooped up its prey like a fishing net before swallowing them whole, similar to how we see modern pelicans feeding.

A croc diversity hotspot

The new species was named in honour of palaeontologist Bryan Patterson (1909-1979), who was an eminent researcher of vertebrate fossils in the Americas. Fossil discoveries indicate that there were now no less than 7 different caimanine species in the Urumaco Formation alone, making it one of the true biodiversity hotspots of crocodylian evolution!

Mourasuchus lived alongside another peculiar, and gigantic, caimanine called Purussaurus. This beast was an apex predator of its time, and would have hunted larger animals, very distinct from the more modest diet of Mourasuchus. By looking at the diets of Purussaurus and the other caimanines that Mourasuchus lived alongside, we can see that there were a whole range of different ecologies present, including fish-feeding types, generalist predators, and even shell-crushing species.

One of the reasons for this high ecological diversity might be related to the climate in South America at the time. During the Miocene, the continent was generally warmer and more humid than it is today. Crocodilians love these tropical climates, which also help to create a large range of different habitats to occupy in an environment. This means lots of animal diversity, which then means there’s a lot of different prey on the menu. Crocodilians seem to have taken advantage of this, and adapted different feeding styles to suit the different food sources available to them.

Featured image source.


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