Adelolophus (/”uh-DELL-oh-LOAF-us”/; “unknown crest”) is a genus of lambeosaurine hadrosaurid dinosaur that lived during the Late Cretaceous period, approximately 80 to 77 million years ago. The name refers to the fact that while it is classified as a hollow-crested hadrosaur, the exact shape of its crest is unknown because only a part of its upper jaw bone has been discovered. Fossils of Adelolophus were found in the Wahweap Formation in Utah, U.S.A. It was first scientifically described in 2014 by paleontologists Terry A. Gates and his colleagues.
Description and Classification
Adelolophus is known only from a single incomplete right maxilla (the main bone of the upper jaw). Because of these limited remains, its full size and appearance are not precisely known. Scientists estimate its features based on its more complete relatives within the Lambeosaurinae subfamily. As a hadrosaurid, or “duck-billed dinosaur,” Adelolophus would have been a plant-eating dinosaur that could walk on two legs or four.
Lambeosaurines, the group Adelolophus belongs to, are known for having hollow, bony crests on their heads. These crests were connected to their nasal passages and might have been used for making sounds, for display to attract mates or recognize members of their own species, or to help regulate temperature. The exact shape of the crest on Adelolophus remains a mystery.
It is considered one of the earliest known lambeosaurines from North America. Its discovery provides important clues about the early evolution of this group of dinosaurs on the continent. It lived alongside other hadrosaurs, such as some species of Gryposaurus.
Distinguishing Features
Due to the fragmentary nature of its fossils, the distinguishing features of Adelolophus are primarily based on the unique characteristics of its maxilla:
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The maxilla shows a combination of features that identify it as a lambeosaurine, such as the shape and position of certain bone surfaces where it connects with other skull bones.
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Specifically, the upward-angling dorsal process of the maxilla is characteristic of lambeosaurines.
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Its age and location in the Wahweap Formation make it distinct, as it represents one of the oldest occurrences of a lambeosaurine dinosaur in North America. This suggests that lambeosaurines may have arrived or evolved in this region earlier than previously thought.
Paleoenvironment and Diet
Adelolophus lived in what is now Utah during the Campanian stage of the Late Cretaceous period. The Wahweap Formation, where its fossil was found, represents an ancient environment that was a broad coastal plain with rivers, floodplains, and swamps. The climate was likely warm and humid.
This environment supported a diverse ecosystem. Adelolophus shared its habitat with other dinosaurs, including horned dinosaurs like Diabloceratops and Machairoceratops, armored ankylosaurs, and carnivorous theropods like Lythronax.
As a hadrosaurid, Adelolophus was a herbivore. It had complex arrangements of teeth known as dental batteries. These batteries contained hundreds of closely packed teeth that formed a broad surface for grinding tough plant material. Its diet likely consisted of conifers, ferns, cycads, and flowering plants that grew in the region.
Significance and Ongoing Research
The discovery of Adelolophus is significant because it pushes back the known fossil record of lambeosaurine hadrosaurs in North America. It provides evidence that these crested dinosaurs were present on the continent earlier than previously understood and contributes to our knowledge of dinosaur diversity in the ancient landmass of Laramidia (western North America). Even though it is known from a single bone, it offers valuable information about the early evolution and spread of lambeosaurines.
Ongoing research related to Adelolophus includes:
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Further paleontological expeditions in the Wahweap Formation with the specific aim of finding more complete fossil material of Adelolophus. Discovering more bones, particularly parts of the skull, would help determine the full shape of its crest and its overall anatomy.
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Detailed comparative studies of the Adelolophus maxilla with those of other early lambeosaurines from North America and Asia to better understand its evolutionary relationships and the migration patterns of these dinosaurs.
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Refining the precise age of the strata within the Wahweap Formation where Adelolophus was found to more accurately pinpoint its place in the timeline of hadrosaur evolution.
The study of Adelolophus highlights how even incomplete fossils can provide important insights into the prehistoric world and the evolutionary history of dinosaurs like Parasaurolophus and Lambeosaurus, which are its more well-known crested relatives.