Recently published in Proceedings of the Royal Society B, scientists in Brazil have found the remains of a prehistoric crocodyliforme that used to roam the oceans of the Paleocene.
The critter has been given the name: Guarinisuchus munizi, which translates out to: Muniz’s warrior crocodile. Despite the “crocodile” in its name, G.munizi was not that closely related to true crocodylians. It was more closely related to the giant pholidosaur Sarcosuchus imperator.
Close relative of Guarinisuchus munizi [left] was Sarcosuchus imperator [right]. Not true crocodiles.
Dyrosaurids first appeared in the Late Cretaceous Period (Maastrichtian age) . During this time they were very scarce, and hard to find. They were shallow marine predators, and in the Cretaceous that niche was already filled by another group of animals: the mosasaurs.
These ancient sea lizards had one of the fastest diversification rates of any vertebrate group studied. They went from nothing to dozens of species with a cosmopolitan distribution and domination of many ecological niches. All of this occurred in the space of only 25 million years! That’s faster than mammal diversification, and faster than dinosaur diversification.
Mosasaurs were showing no signs of slowing down right up to the K/T asteroid event. After that, they disappeared.
That’s when the dyrosaurids started taking over.
Analysis of Guarinisuchus munizi material has found that it is more closely related to African taxa than its geographically closer relatives in North America. This suggests that dyrosaurids had crossed the Atlantic ocean from Africa sometime before the K/T event. After said event, the vacant niches left by the mosasaurs were quickly snatched up by these dyrosaurids, as they moved up North, and eventually, worldwide.
It is interesting to see how this group of animals was apparently held back during their earlier evolution. Yet, if they hadn’t been held back; if they had out-competed mosasaurs for the top spot in the food chain, then they wouldn’t have survived the K/T event.
It’s funny – and completely make believe – but it almost appears as if dyrosaurids were already setting themselves up to take over. It’s almost as if they knew…
They didn’t of course, but it’s fun to pretend that they did. >:)