Amargasaurus cazaui is certainly a peculiar sauropod, a broad class of dinosaurs. Skeletons show it had spine-like features along its neck and back, which have puzzled paleontologists for a while. Were they visible spikes or the nubs of horns or were they something else? Researchers are now thinking that the answer might be a sail or crest-like structure.

As reported in the Journal of Anatomy, a team led by Dr Ignacio Cerda of the Carlos Ameghino Provincial Museum, Argentina, looked at the spines – technically the elongated hemispinous processes – of this and similar species in detail. They were looking at evidence that would differentiate between horns, a sail, or maybe a hump like a bison. What they found was evidence of ligaments between the spines pointing towards the sail hypothesis.

“We searched for previous hypotheses about the possible soft tissues associated to the elongated hemispinous processes of Amargasaurus and another dicraeosaurid sauropod with similar spines, but whose species is unknown. We found two main hypotheses: the neck with “horns” and the neck with “sails”,” Dr Cerda told IFLScience. “Since a deep study searching anatomical and histological evidence to test these hypotheses was never conducted before, we considered that will be really important to search evidence to contrast these previously mentioned hypotheses.”

Based on the current research such a sail might have been used as a display device, a very broad term that could cover a variety of behaviors and uses including attracting partners and mating, competing with other members of the species, and even as a deterrent against predators. The team actually calls for the functional significance of these “bizarre structures” to be analyzed with different approaches.

But it is not a question of function that eludes the researchers, it’s also a question of morphology. What did these sails actually look like? Dr Cerda said they can’t be certain based on current data. More work will be necessary to improve on this.

“Note that we found a particular distribution of mineralized fibers that are to different types of soft tissues, including ligaments. We consider that these ligaments possibly connected successive spines, which finally results in a cervical sail… as you see, we are still far away to determine how such a sail looked like,” Dr Cerda, who is also part of the Consejo Nacional de Investigaciones Científicas y Técnicas, told IFLScience.

Understanding what dinosaurs really looked like is a fascinating puzzle, and we are certain we haven’t seen the last (and the last artist's impression) of the peculiar Amargasaurus.