Aquilops is a genus of ceratopsian dinosaur that lived in North America during the Early Cretaceous, about 109-98 million years ago. In 1997, the only known skull was found in the Cloverly Formation of Carbon County, southern Montana, and was made the holotype specimen of the new genus and species Aquilops americanus in 2014. The generic name is derived from the Latin and Greek words for "eagle" and "face", in reference to the dinosaur's hooked beak, and the specific name refers to it being the first early neoceratopsian (ceratopsians with a neck-frill) found in North America. The holotype consists of a partial skull and lower jaws of a probably subadult individual. Aquilops was prominently featured in the 2025 film Jurassic World: Rebirth, an occasion used for scientific outreach.
Aquilops was a small neoceratopsian, and the only known skull is long as preserved, from which a total length of about and a weight of about has been extrapolated. A fully grown Aquilops would probably have been or less. As an early ceratopsian, it would probably have been bipedal. The upper margin of the skull in front of the eyes is steeply inclined, and the skull is triangular when seen from the top. Aquilops is unique in that the rostral bone at the front of the snout is strongly hooked and has a boss at the front edge. The rostral forms a unique, concave profile in front of the upper teeth. The antorbital fenestra (an opening in front of the socket) is unique in being twice as long as tall and in tapering to a sharp point below the orbit.
Aquilops is one of the oldest known ceratopsian from North America, and was more closely related to Asian ceratopsians than to North American ones. This suggests there was an interchange of neoceratopsians between North America and Asia during the Aptian. Aquilops has been found to be one of the most basal (early diverging) neoceratopsians, with one study finding it to be the sister taxon of Sasayamagnomus from Japan. Aquilops would have been a plant-eater, using its hooked beak to nip at vegetation. The Cloverly Formation is dated to either the Albian or Cenomanian stages of the Early Cretaceous. The Himes Member of the formation which Aquilops is known from represents a braided river system.
Discovery and naming
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 where he lived, to prepare it under a microscope, and discovered it did not match the other animal, but, based on its beak, belonged to a little ceratopsian (horned) dinosaur. Until then, the Early Cretaceous fossil record of this group from North America consisted of isolated teeth and bones which could not be further identified and provided little information about the early evolution of this group there.
After finishing the preparation of the skull, Madsen 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 Mathew 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.
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 (ceratopsians with a neck-frill, unlike the small shelf of more basal or earlier diverging members like Psittacosaurus and Chaoyangsauridae) 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 consists of a partial skull with associated predentary (frontmost bone of the lower jaw which formed the lower beak) and partial left (tooth-bearing bone) 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 front end of the , the braincase, and most of the palatal bones are missing. The specimen was probably a subadult individual. 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 American ceratopsians.
Farke stated in a blog post associated with the publication 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. Since 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 better known relatives such as Archaeoceratops and the more distantly related Psittacosaurus, since the body-plans of early ceratopsians were fairly similar.
Farke explained to science reporters that Aquilops was significant for being about 20 million years older than the next oldest ceratopsian dinosaur from North America known at the time, 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 its 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. This occasion was subsequently used for scientific outreach. 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" 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 Skull
Aquilops was a small neoceratopsian, and the only known and presumably subadult skull is long as preserved, from the tip of the rostral bone (the frontmost bone of the snout which formed the upper beak in ceratopsians) at the front to the tip of the ("cheek" bone) at the back. It is 60% the size of the presumed adult Liaoceratops and Archaeoceratops holotype specimens, but the same size as a juvenile Liaoceratops. The predentary bone (which formed the beak of the lower jaw) is while the preserved part of the dentary (the tooth-bearing bone of the lower jaw) is . Extrapolating from Archaeoceratops, Wedel estimated the total body length of Aquilops to have been about and its weight about in a blog post. He noted its size had variously been compared to that of a raven, rabbit, or a cat. He added that a fully grown Aquilops would have been larger, though not much more than Archaeoceratops, probably or less in total length. As an early ceratopsian, Aquilops would have had a large head, long hindlimbs, shorter forelimbs, a long tail, and probably been bipedal.
The orbit (eye socket) of Aquilops is comparatively large in relation to the skull and the bones are not very textured, and based on reconstructed growth series of other ceratopsians, it was not a fully grown. Other of its features (such as the accessory ridges of the maxillary teeth being well-defined and the contact between the jugal and in front of the eye being elongated) are found in many adults but not necessarily in juveniles, and this combination of features along with its intermediate size indicates it was a subadult. The upper margin of the skull in front of the eyes was steeply inclined compared to the portion behind. The width of the frontal bones in relation to the surrounding part indicate that the skull was triangular when seen from the top, though maybe not as strongly as in larger species. The lesser triangularity may be due to the specimen being juvenile, similar to what is seen in Protoceratops.
The rostral bone of Aquilops is not as elaborate as those of later ceratopsids such as Triceratops, with short upper and side processes. The front surface is sharply keeled, more so than in Yamaceratops, but less than in Protoceratops and Leptoceratops. There is a boss or rugosity at the midline front edge of the rostral, which is unique among ceratopsians. The boss is long by tall. Farke noted that he did not think this feature was a displaced piece of bone or pathological (caused by damage) due to its texture not matching that, and would have been present in the live animal. The side profile of the front edge of the rostral is strongly arched, in contrast to the more gently arched edge in other ceratopsians. The lower margin of the rostral is strongly hooked, and as articulated with the premaxilla (the frontmost tooth-bearing bone of the upper jaw) behind it, the rostral tip forms a nearly 90 degree angle with the line of the upper teeth of the maxilla (the hindmost tooth-bearing bone), a distinct feature of Aquilops. This angle is much broader in other neoceratopsians, for example about 150 degrees in Liaoceratops, and makes the rostral tip point downwards.