Aquilops

Aquilops Temporal range: Early Cretaceous,
Holotype skull seen from the sides (left), above, and below (right)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Ceratopsia
Clade:	†Neoceratopsia
Genus:	†Aquilops Farke et al., 2014
Species:	†A. americanus
Binomial name
†Aquilops americanus Farke et al., 2014

Aquilops is an early herbivorous ceratopsian dinosaur dating from the Early Cretaceous of North America, approximately 109 million to 104 million years ago. The type species is A. americanus.

Discovery and naming

Holotype locality (blue arrow) within Cloverly Formation outcrops (orange)

In 1997, an expedition funded by the National Geographic Society and led by the paleontologist Richard L. Cifelli searched for microfossils, mammals and lower cretaceous rocks along the border of Montana and Wyoming. In the Cloverly Formation of Carbon County, southern Montana, the volunteer paleontologist Scott K. Madsen noticed a grapefruit-sized bit of white on a rock, picked it up and noticed it contained teeth, realizing it was a skull of rare size. He brought it to his camp, where it was already clear the teeth belonged to a plant-eating dinosaur, assumed by researchers to belong to Zephyrosaurus, the only dinosaur known from there of that size.

Madsen brought the skull to Vernal, Utah, to prepare it under a microscope, where he discovered it did not match the other animal, but, based on its beak, belonged to a little ceratopsian (horned) dinosaur. After finishing its preparation, he turned it over to researchers he was working with at the Sam Noble Oklahoma Museum of Natural History, where it was catalogued as specimen OMNH 34557. Cifelli and the paleontologist W. Desmond Maxwell began work on a scientific description, but other commitments postponed it. Cifelli's graduate student Matt J. Wedel moved into the same town as the paleontologist Andrew Farke, who had experience with ceratopsians, and suggested he was brought onto the project, which commenced in 2010. By this time, there had been many rumors of an Early Cretaceous ceratopsian skull from Montana, so Farke was pleased to join. Wedel described his role in the project as "social glue" and drawing the skull reconstruction.

Holotype skull (below) with reconstruction and replica (above) as exhibited in Sam Noble Oklahoma Museum of Natural History

While originally meant to be a short article, the authors decided to write a monograph to do the specimen justice, with room for additional information and figures. In 2014, the specimen was made the holotype of the new genus and species Aquilops americanus by Farke, Maxwell, Cifelli, and Wedel. The generic name is derived from the Latin word aquila, meaning "eagle", and the Greek ὤψ, ops, meaning "face", in reference to the dinosaur's hooked beak. The specific name americanus refers to the species being the first unequivocal early neoceratopsian found in North America. The online article contained downloadable 3D models based on surface scans of the skull (which Wedel pointed out can be 3D printed by anyone) as well as paleoart life restorations by the artist Brian Engh, with additional artwork made to publicize the specimen.

The holotype specimen consists of a partial skull with associated predentary and partial left dentary of the lower jaws, along with unidentified fragments. The skull is somewhat skewed to the right, along with some compression from side to side and top to bottom, which mainly affects the upper part. The right side of the skull is more complete and better preserved than the left. The specimen was probably a subadult individual. The front end of the rostral nasal bones, the braincase, and most of the palatal bones are missing. The lemon-sized skull is exhibited in Sam Noble Museum's Hall of Ancient Life alongside a Pentaceratops, which holds the Guinness World Record for having the largest skull known among dinosaurs, and was one of the largest and latest North Americam ceratopsians.

Publicity artwork showing Aquilops being held by a human, by Brian Engh

Farke stated that the age of the specimen could not be determined through sectioning due to the lack of limb bones which are the most reliable way of determining growth stages. While dinosaur features can change as they age, naming new species based on young specimens can be problematic, but Farke noted that even if the skull belonged to a young individual, it was distinct enough in features that would be stable throughout life, so that they would be recognizable in an adult. While only the skull was known, the authors wanted to include the body in the artwork used to publicize the find by Engh, which they based on relatives with better known body-plans, such as Archaeoceratops and the more distantly related Psittacosaurus.

Farke explained to science reporters that Aquilops was significant for being about 20 million years older than the next oldest horned dinosaur from North America, and about 40 million years older than the iconic Triceratops. He added that the authors were surprised that Aquilops was more closely related to Asian ceratopsians than to North American ones, and that this left him wondering when the ancestors of the other horned dinosaurs of North America immigrated there. Wedel noted that whatever attention Aquilops would get was probably going to be due to Engh's artwork.

In 2025, Aquilops was prominently featured in the film Jurassic World: Rebirth and widely appeared in the film's promotion and merchandise. In the film, an Aquilops nicknamed "Dolores" is carried in a backpack, which was realized through animatronics so that the actors could interact with it. The city of Norman, where the Sam Noble Museum is located, recognized June 29 through July 5, 2025, as Natural History Week in honor of its newest "paleo-celebrity" Aquilops and its scientific significance. To celebrate the appearance in the film, the museum hosted Aquilops Day on July 19 with various activities. Madsen, Wedel, and Farke expressed excitement over the film and satisfaction at how accurately the dinosaur was depicted, with Wedel stating “I started out as a dinosaur-obsessed little kid, and I was lucky to pursue a career in paleontology. Now Aquilops is going to be a lot of kids’ favorite dinosaur, and maybe it will help inspire the next generation to explore and discover.”

Description

Hypothetical life restoration of the head by Engh

The skull is 84.2 mm (3.3 in) long. The holotype is possibly not from a full-grown individual. A comparison with related species indicates it might have been at 60% of its adult length. Wedel estimated the total body length of Aquilops at 60 cm (23.6 in) and its weight at 1.5 kg (3.3 lb). Its size has been compared to that of a house cat or a rabbit.

The authors established some unique traits. The rostral, the bone core of the snout beak, curves downwards and has an arched keel on its top with a bump on the front. In front of the tooth row the upper jaw rim is over its total length concave in side view. The skull opening, the antorbital fenestra, is twice as long as it is tall and has a pointed rear, below the eye socket.

Classification

3D scans of the holotype cranium (above) and lower jaws (below); click thumbnails to turn the models around

Lower jaw

Co-describer Matt Wedel with reconstructed Aquilops skeleton at DinoCon

Aquilops was placed in the Neoceratopsia. A cladistic analysis showed that it was positioned rather basal, below Leptoceratops in the evolutionary tree, with only Liaoceratops being more basal. A more derived position, e.g. as a leptoceratopsid or a protoceratopsid, was less likely; it was improbable that it was a ceratopsoid. The fact that the holotype was a subadult might have distorted these results because juvenile individuals often show basal traits. However, after correcting for traits that might change during ontogeny, the resulting tree was basically the same. The ceratopsians more derived than psittacosaurids, called neoceratopsians, evolved in Asia: the presence of a basal neoceratopsian in North America was seen as an indication for a late Early Cretaceous migration event, the ancestors of Aquilops invading from Asia. Two later such events would have occurred in the early Late Cretaceous.

Marginocephalia	Pachycephalosauria Stegoceras Ceratopsia Yinlong Xuanhuaceratops Chaoyangsaurus Psittacosaurus P. sinensis P. mongoliensis Neoceratopsia Liaoceratops Aquilops Auroraceratops Yamaceratops Helioceratops Archaeoceratops Koreaceratops Leptoceratopsidae Coronosauria

Paleoenvironment

Reconstructed skull from the side and above

Aquilops is known from Unit VII also known as the Himes Member of the Cloverly Formation of Montana, which has been dated to about 104–109 million years ago, during the middle to early late Albian of the Early Cretaceous. At the end of Cloverly times, the shallow sea would expand to cover the entire region and would eventually split North America completely in half, forming the Western Interior Seaway. Abundant fossil remains of coniferous trees suggest that these plains were covered in forest. Grasses would not evolve until later in the Cretaceous, so Early Cretaceous dinosaurian herbivores browsed from a variety of conifers and cycads.

Restoration of Cloverly formation environment with the mammal Gobiconodon pursuing juvenile Aquilops while adults attempt to protect them, by Engh

The most abundant herbivorous dinosaur of the time was the large iguanodont Tenontosaurus. The smaller hypsilophodont Zephyrosaurus, the nodosaur Sauropelta, titanosaurs, and a type of ornithomimosaur also lived there. The dromaeosaurid theropod Deinonychus fed upon some of these herbivores, and the sheer number of Deinonychus teeth scattered throughout the formation are a testament to its abundance. Microvenator, a small basal oviraptorosaur, hunted smaller prey, while the apex predators of the Cloverly was the large carcharodontosaurid theropod Acrocanthosaurus. Lungfish, triconodont mammals, and several species of turtles lived in the Cloverly, while crocodilians prowled the rivers, lakes, and swamps, providing evidence of a year-round warm climate.

See also

• 2014 in paleontology
• Neoceratopsia
• Timeline of ceratopsian research

External links

• Aquilops americanus - video about the display at Sam Noble Oklahoma Museum of Natural History
• The Aquilops has his day at the Sam Noble Museum - news report about Aquilops's popularity following Jurassic World: Rebirth