The frilled serpentsaur split from its ancestors to live its entire life in the desert. The major change to the organism is its new neck frills. These frills serve two purposes: they keep the serpentsaur cool via thermoregulation, and secondly they can be puffed out on either side of its head when threatened by other serpentsaurs to make itself look larger (as can be seen in the picture). The spikes that make up these frills aren't poisonous like the organism's other spikes. It has also grown somewhat larger, thanks to its ability to hunt during the day and night (though it still needs to sleep of course, and it will avoid hunting during the hottest part of the day). Finally, its tail spike has grown larger to make it more deadly.
Artwork by OviraptorFan