Description and Classification

Jeyawati was a plant-eating dinosaur that walked primarily on two legs but could also move on all fours. Based on the incomplete fossils found, which include parts of the skull, vertebrae, ribs, and limb bones, scientists estimate it was a medium-sized hadrosauroid, possibly reaching lengths of around 4 to 5 meters (13 to 16 feet). As a hadrosauroid, Jeyawati belonged to a group of ornithopod dinosaurs closely related to the later, more famous “duck-billed” dinosaurs, the hadrosaurids, such as Edmontosaurus or Parasaurolophus.

Jeyawati is considered an early, or basal, member of the Hadrosauroidea. It shows some features that are more advanced than earlier relatives like Iguanodon, particularly in its jaw and tooth structure, which were adapted for efficiently chewing tough plant material. However, it was not as specialized as the true hadrosaurids. Its classification places it as more derived (more evolved) than some other early hadrosauroids like Eolambia, but less derived than the members of the Hadrosauridae family. Its teeth were arranged in rows that could replace worn ones, forming a grinding surface, a precursor to the complex dental batteries seen in later duck-billed dinosaurs.

Distinguishing Features

Jeyawati possessed several features that help paleontologists identify it and understand its place in dinosaur evolution. These include:

• A unique “wrinkled eye” feature, which is a rough, grooved texture on the surface of the postorbital bone (a bone located behind and above the eye socket). This is the characteristic that gives the species its name, rugoculus.
• Specific details in its jaw bones (dentary and maxilla) and teeth that show a mix of primitive and advanced hadrosauroid traits. For example, it had more tooth positions than very early iguanodontians but fewer than advanced hadrosaurids.
• The teeth were designed for grinding and shredding plants, indicating its role as an herbivore. While it had replacement teeth, its dental battery was likely not as complex or extensive as those found in later hadrosaurids like Maiasaura.
• Its overall body plan was typical of an early hadrosauroid, built for browsing on vegetation.

Paleoenvironment and Diet

Jeyawati lived in what is now New Mexico during the Turonian stage of the Late Cretaceous. At that time, this region was part of a warm, humid coastal plain near the edge of the Western Interior Seaway, a large inland sea that split North America in two. The environment likely consisted of forests, swamps, and river systems, supporting a diverse range of plant life.

As an herbivore, Jeyawati‘s diet would have consisted of the plants available in this ecosystem. Its “grinding mouth” and specialized teeth were well-suited for processing tough vegetation such as ferns, conifers, cycads, and early flowering plants. Jeyawati shared its habitat with other dinosaurs, including the small tyrannosauroid Suskityrannus, the early ceratopsian Zuniceratops, and the therizinosaur Nothronychus. These animals formed part of a unique coastal ecosystem.

Significance and Ongoing Research

The discovery of Jeyawati is significant because it provides valuable information about the early evolution and diversification of hadrosauroids. These dinosaurs were an incredibly successful group during the Late Cretaceous, and Jeyawati helps paleontologists understand the steps they took to get there. It represents an intermediate form, filling a gap in the fossil record between more primitive iguanodontian relatives and the highly specialized hadrosaurids.

Jeyawati’s fossils also offer a glimpse into the types of dinosaurs that lived in North America during the Turonian stage, a period that is not as well-documented as later parts of the Cretaceous in some areas. Ongoing research may involve further analysis of the known Jeyawati fossils, comparisons with newly discovered hadrosauroids, and the search for more complete specimens. Such studies could help refine its exact position in the hadrosauroid family tree and provide more details about its biology and behavior, including the possible function of its “wrinkled eye” feature, which might have been used for display or species recognition.