Description and Classification

Drinker was a relatively small and agile dinosaur. It is estimated to have been about 2 meters (around 6.5 feet) in length and to have weighed between 10 and 20 kilograms (22 to 44 pounds). As an herbivore, it walked on two legs (bipedal) and had a light build. Its hind limbs were slender and well-suited for running, while a long tail likely provided balance. Its forelimbs were considerably shorter than its hind limbs.

Drinker belongs to the order Ornithischia, which are known as “bird-hipped” dinosaurs, and is more specifically considered a basal (early or primitive) ornithopod. Ornithopods are a diverse group of plant-eating dinosaurs that later included larger and more famous dinosaurs like Iguanodon and the hadrosaurs (also known as duck-billed dinosaurs). Drinker is thought to be closely related to other small ornithopods from the Morrison Formation, such as Nanosaurus, which now includes specimens formerly assigned to genera like Othnielia and Othnielosaurus. The precise position of Drinker within the early ornithopod family tree is still studied by scientists, but it represents an early form in the evolutionary history of this successful dinosaur group.

Distinguishing Features

Drinker can be identified by several key characteristics related to its anatomy and potential behavior:

• Its small body size, which made it one of the smaller plant-eaters in its environment.
• A pubis bone (part of the hip) that was oriented horizontally and pointed backward, a typical feature of ornithischian dinosaurs.
• Teeth adapted for processing plants, including leaf-shaped cheek teeth that were effective for shredding tough vegetation.
• Possible burrowing behavior. Multiple skeletons of Drinker, including those of young and adult individuals, were discovered together in a concentration of fossils that has been interpreted as a filled-in burrow or den. This suggests a rare behavior for dinosaurs.

Paleoenvironment and Diet

Drinker inhabited the famous Morrison Formation of North America during the Late Jurassic. This extensive region was characterized by a semi-arid climate with seasonal rainfall. The landscape included river systems, floodplains, and open woodlands. The vegetation was dominated by plants such as ferns, cycads, ginkgoes, and conifers; flowering plants were not yet common. Drinker likely fed on low-growing vegetation, using its beak-like mouth to snip off plant parts and its specialized cheek teeth to grind them.

In this rich ecosystem, Drinker coexisted with a diverse community of other dinosaurs. These included giant long-necked sauropods like Apatosaurus, Diplodocus, and Brachiosaurus; large carnivorous theropods such as Allosaurus and Torvosaurus; and other plant-eating ornithischians, for instance, the armored Stegosaurus and the larger ornithopod Camptosaurus. As a small herbivore, Drinker would have needed to be alert to predators and probably relied on its speed, and possibly its burrowing abilities, for safety.

Significance and Ongoing Research

The discovery of Drinker is important because it contributes to our understanding of the variety of small herbivores that lived in the Morrison Formation, an ecosystem often recognized for its giant dinosaurs. Drinker shows that smaller animals also played significant roles in the ancient food webs.

The most fascinating aspect of Drinker is the hypothesis that it was a burrowing dinosaur. Finding several individuals together, apparently in a den-like structure, hints at complex social interactions and a unique adaptation for dinosaurs of that era. If this burrowing behavior is confirmed, Drinker would be one of the few non-avian dinosaurs known to have dug dens, a behavior also proposed for the later, distantly related Cretaceous dinosaur Oryctodromeus. Ongoing research aims to find more evidence for this behavior, as well as to clarify Drinker’s precise evolutionary connections to other early ornithopods like Nanosaurus. Studying these small dinosaurs helps scientists piece together the early evolution of ornithopods, which eventually became one of the most successful and widespread groups of herbivorous dinosaurs.