Mounted skeleton from Petrified Forest National Park, AZ.
Reconstruction by Jeff Martz.
When: Late Triassic (~225 - 200 million years ago)
Where: South Western United States, North America.
What: Desmatosuchusis an Aetosaur. This is a group of archosaurs that ranged worldwide during the Triassic.In the archosaur family tree, they are on the line leading to crocodiles, not birds, and thus are croc-line archosaur or a member of the Crurotarsi.
Desmatosuchus is one of the last aetasaurs known, and is many ways is a fairly representative member of this clade. It was covered in armor plating on its back, belly, and tail. One thing that sets Desmatosuchus apart from its fellows is the two parallel rows of spikes that ran along its back on the edge of its osteoderm plating. The largest of these spikes were roughly above the shoulders and could be up to 18 inches (~45 centimeters) long. Pretty impressive on an animal that is ‘just’ 16 feet (~ 5 meters) long.
Desmatosuchus was an herbivore, so all of this armor was to try to protect it from the variety of predators that it co-existed with, such as some of the first true dinosaurs. The turned up shovel-shaped snout of Desmatosuchus coupled with its relatively weak teeth indicate this animal probably fed on softer plant material, digging though the soil to find roots and tubers. That being said, it has been proposed in the past that it was digging not for flora, but for fauna, feeding upon unearthed grubs and other insects. It is possible that Desmatosuchus had a more broad diet than has been previously assumed.