Description and Classification

Willinakaqe was a type of ornithopod dinosaur, belonging to the family Hadrosauridae, commonly known as “duck-billed” dinosaurs due to the shape of their snouts. Like other hadrosaurs, it was a plant-eater and could likely walk on both two legs (bipedally) and four legs (quadrupedally). Estimates suggest it could grow to a considerable size, typical for hadrosaurs, possibly around 9 meters (30 feet) in length. Its classification has been a subject of scientific discussion. Initially, it was thought to be a saurolophine hadrosaur, a group that often lacks large head crests or has solid crests. However, later research has suggested it might be a kritosaurin, a group often characterized by prominent nasal arches, similar to dinosaurs like Kritosaurus. Some scientists also propose that the fossils found might belong to young individuals of another known hadrosaur, or even that Willinakaqe is a “nomen dubium,” meaning a doubtful name because the available fossils may not be distinct enough to definitively identify it as a unique genus.

Distinguishing Features

Identifying unique features for Willinakaqe is challenging due to ongoing debates about its classification. However, based on the fossils originally assigned to it, some characteristics were noted:

• It possessed the typical hadrosaur “duck-bill” shaped snout, which was broad at the tip and toothless, likely used for cropping vegetation.
• Inside its jaws, it had complex dental batteries – many tightly packed teeth that formed a grinding surface for processing tough plant material.
• The original description highlighted specific details of its skull bones, such as the shape of the premaxilla (the bone at the front of the upper jaw) and the postorbital bone (a bone located behind the eye socket), which were initially thought to set it apart. However, the distinctiveness of these features is now under review by paleontologists.
• As a hadrosaur, it would have had strong hind limbs for walking and running, and somewhat shorter forelimbs.

Paleoenvironment and Diet

Willinakaqe lived in southern South America during the end of the Cretaceous period. The Allen Formation, where its fossils were discovered, represents an environment with rivers, floodplains, and lakes, possibly near a coastal area. The climate was likely warm and relatively humid. This ecosystem also supported a variety of other life forms, including other dinosaurs like large titanosaur sauropods (e.g., Aeolosaurus), predatory abelisaurid theropods (e.g., Carnotaurus), and other types of ornithischian dinosaurs. As a hadrosaur, Willinakaqe was a herbivore. Its diet would have consisted of the available plant life, which likely included conifers, cycads, and early flowering plants. It would have used its broad beak to gather vegetation and its powerful dental batteries to grind it down efficiently.

Significance and Ongoing Research

The discovery of Willinakaqe was significant because it added to the known diversity of hadrosaurs from the Southern Hemisphere, specifically from Patagonia, a region rich in dinosaur fossils. Hadrosaurs are more commonly known from North America and Asia, so finds in South America, like Willinakaqe, are important for helping paleontologists understand how these large herbivores spread across the ancient supercontinent of Gondwana and later to other parts of the world. Ongoing research primarily focuses on clarifying the classification and validity of Willinakaqe. Scientists are re-examining the fossil material and comparing it with other hadrosaurs from South America and elsewhere. This research aims to determine if Willinakaqe is indeed a distinct genus, or if its fossils represent a previously known dinosaur, perhaps a juvenile. Understanding its true identity will help paint a clearer picture of hadrosaur evolution and biogeography during the Late Cretaceous in Gondwana.