Adelolophus
Oldest North American lambeosaur, known only from a broken maxilla.
Adelolophus, meaning "unknown crest," is a genus of lambeosaurine dinosaur, a type of crested duck-billed dinosaur, found in Upper Cretaceous rocks in Utah. The only known species is *Adelolophus hutchisoni*, represented solely by a broken maxilla, or upper jawbone. It is the oldest lambeosaur fossil discovered in North America and the only lambeosaur species known from the Wahweap Formation.
The fossil locality near Death Ridge in Kane County, Utah, was first reported in 1973 by Howard D. Zeller. In 1999, John Howard Hutchison and colleagues returned to collect fossils there, including the maxilla. This bone was first described in a 2013 paper by Terry Gates and colleagues, who noted its unique morphology but did not name it. The species was formally named in a 2014 study led by Gates, published in the book *Hadrosaurs*. The holotype, UCMP 152028, is an incomplete right maxilla with both ends broken. The name comes from Greek roots meaning "not," "to show," and "crest," referencing that the known anatomy does not reveal the presumed crest. The specific name honors Hutchison. The exact locality was initially uncertain, but a 2016 study by Hutchison and Patricia A. Holroyd confirmed it came from the lower end of the Upper Member of the Wahweap Formation. The locality may bridge the time gap between the older Middle Member and younger Upper Member. Other fossils from the same site include fragmentary hadrosaur postcranial bones of various ages, including one very large individual, though these cannot be confirmed as belonging to *Adelolophus*.
Despite its fragmentary nature, the maxilla shows several unique traits that diagnose it as a distinct genus. Its triangular shape identifies it as a lambeosaur. Among relatives, its anatomy is more similar to parasaurolophs (tube-headed lambeosaurs) than to lambeosaurins (casque-headed lambeosaurs). It differs most notably in its very tall medial wall along the upper edge of the bone, both front and back. Lambeosaurins have a short medial wall, while *Parasaurolophus* shows an intermediate condition. The dorsal process is rounded, like that of parasaurolophs, rather than sharply tapered. The articulation area with the jugal bone suggests a parasauroloph-like jugal, though that bone is not preserved. Near the back of the maxilla, the palatine process is large and elevated, unlike the smaller, lower process in other lam
- field
- Paleontology
- known_for
- Oldest known lambeosaur remains in North America; only lambeosaur from the Wahweap Formation
- type_species
- Adelolophus hutchisoni
- holotype
- UCMP 152028
- age
- Early Campanian (Upper Cretaceous)
- location
- Kane County, Utah, USA
Lore & Background
A fossil locality near Death Ridge in Kane County, Utah, was first reported in 1973 by Howard D. Zeller. John Howard Hutchison and colleagues collected fossils there in 1999, including the maxilla of a lambeosaurine hadrosaur. The specimen was first reported in a 2013 paper by Terry Gates and colleagues, who noted it as the only known lambeosaur material from the formation and the oldest in North America, but refrained from naming it. The specimen was described and named in a 2014 study led by Gates, published in the book Hadrosaurs, as Adelolophus hutchisoni. The generic name derives from Greek elements meaning 'not', 'to show', and 'crest', referring to the unknown crest. The specific name honors Hutchison. The exact locality was clarified by a 2016 study by Hutchison and Patricia A. Holroyd, confirming it came from the lower end of the Upper Member.
Reader's Guide
Adelolophus is significant as the oldest known lambeosaurine from North America, providing a key data point for understanding the early evolution and dispersal of crested hadrosaurs on the continent. Despite its fragmentary nature—only a broken maxilla—its unique morphology allowed it to be diagnosed as a distinct genus. Phylogenetic analyses place it within Parasaurolophini, closely related to Parasaurolophus and Charonosaurus, and sister to Tlatolophus. Its environment in the Upper Member of the Wahweap Formation was tidal and estuarine, with a wet climate but a dry season, shared with fish, turtles, and other dinosaurs including tyrannosaurids and ceratopsids. The specimen's uncertain locality was later resolved, and associated fragmentary hadrosaur postcranial remains may belong to Adelolophus but cannot be confirmed.
Did You Know?
- Adelolophus means 'unknown crest' because the crest is not preserved in the only known specimen.
- The holotype is an incomplete right maxilla with both ends broken off.
- Adelolophus is the only known lambeosaur species from the Wahweap Formation.
- The exact locality of the holotype was unknown at the time of naming and was clarified in a 2016 study.
More in Dinosaur genera 1-24
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