Behemoth dinosaurs evolved from small ancestors more rapidly than paleontologists thought

They preserve quite a unique environment, one that would continue until the Triassic ended. Many of the animals here have been found in fossilized volcanic ash. The old image of prehistoric animals doing battle under the shadow of puffing volcanoes might have held some water here. The volcanoes here were active indeed, dumping ash quite regularly. There were also lakes and river systems in the area so the Chañares might have been pretty much an eden. Dinosauromorphs still lived as speedy omnivores that didn't really have much of a role in the ecosystem, instead filling a relatively weasel-like niche.

One of the best-known dinosauromorphs is Marasuchus. This animal was just like any other member of its family and while it is indeed one of the most publicized of its kind it is still relatively unknown to the general public. Marasuchus was a 40-centimeter dwarf. It was thin and had grossly elongated feet and hind legs, and could probably run on two feet for short periods.

Marasuchus gets its name from the mara, the Patagonian rodents that mimic small deer in their habits. Today the mara is a common sight on the pampas grasslands, living in large colonies and running around nibbling grass and other small plants. Marasuchus' body plan was not the dinosauromorph gold standard, though.

The dinosauromorphs actually came in all shapes and sizes, with the silesaurs being radically different from Marasuchus. They walked mostly on all fours. In fact they may have seemed like a cross between a small dog and an early dinosaur. The Chañares contains the meter-long Lewisuchus. It too would have been a speedy little animal, a warm-blooded beast that could, like Marasuchus, sometimes rear up on two legs. However in silesaurs, the difference in limb lengths is not as drastic as in Marasuchus. None of these animals were true giants, at least not in the way that the later non-avian dinosaurs would become.

Vasika
Udurawane

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