On the rocky slopes of the Argentine Andes, a team of paleontologists has unearthed an “almost complete and perfectly articulated” skeleton that lived here 230 million years ago. In the world of paleontology, every time there is a new discovery that sheds light on the real evolution of dinosaurs, we have to rewind and examine everything.
The specimen in question is a Huayracursor jaguensis, a dinosaur that, despite its modest size, shared traits with the giants long before they ruled the earth. Having the same characteristics as these future colossi—for example, a long neck and large size—everything seems to indicate that there was an evolutionary process that began gradually in the Triassic Period, just when dinosaurs were taking their first steps.
What is a Huayracursor jaguensis dinosaur?
The name of this dinosaur combines the indigenous Quechua language with Latin. Literally, it could be called “Wind Runner of Jagüé.” This dinosaur lived on Earth during the Late Triassic period, 230 million years ago. Scientists consider this period to be the adolescence of our planet Earth, since the supercontinent Pangea was still intact.
This particular dinosaur was relatively small, measuring about 2 m long and weighing about 18 kg. This made it almost twice as large as other early dinosaurs in the area, although it looked like a miniature compared to the giants that would come 50 million years later (which would weigh several tons). What makes Huayracursor special is its genetic lineage and anatomy: it was a primitive sauropodomorph, making it the “great-great-grandfather” of the iconic long-necked sauropods, such as Argentinosaurusand Brachiosaurus.
Its neck is its most important feature: it had elongated cervical vertebrae in an incipient form, which means that the evolutionary path towards the familiar giraffe neck was already underway. This gave it a key dietary advantage: while its smaller cousins were forced to eat only low-growing plants at ground level, the neck of the Huayracursor allowed it to be selective. In other words, it had a much wider selection of flora to choose from: leaves, shoots, cones. It could reach the top of the bushes, ascending to a food source that other terrestrial herbivores could not reach.
The Triassic Ecosystem
To understand the diet and life of this dinosaur, we have to discard our current idea of the Argentine Andes. This area was not dry and rocky, but was in the Carnian Pluvial Episode (CPE). This period was marked by intense and prolonged rainfall, which changed the global climate and the landscape of La Rioja. What is now a desert was then a lush low-lying sedimentary basin, with lakes and floodplains that fed dense and diverse vegetation. This dinosaur had plenty to choose from, as the dominant flora on its menu is known as Dicroidium Flora.
This vegetation was not the flowering plants we know today, but gymnosperms (such as conifers and cycads), which included plants very similar to ferns, but which were capable of producing seeds and wood. But how do we know what kind of vegetation existed at that time? Although it sounds a little strange, we know about this dinosaur diet thanks to nearby findings such as coprolites, which are fossilized feces from other herbivores that inhabited the area at the same time.
In this humid and lush world, the Huayracursor was a simple primary consumer (a herbivore, in other words). In fact, it is suspected that it was potential prey for the true apex predators, the Rauisuchids, enormous archosaur reptiles (relatives of crocodiles).
Other animals that coexisted with the Huayracursor include the small carnivore Eoraptor lunensis(weighing about 11 kg), just like the Ischigualasto, which is considered one of the oldest dinosaurs in the world. A few million years later, this same region of La Rioja saw the emergence of much larger dinosaurs, such as Riojasaurus incertus, which already reached 10 meters in length. Everything seems to indicate that Huayracursor evolved rapidly into gigantism… like that typical scrawny cousin who has a growth spurt once he hits puberty and surprises everyone at the family reunion.