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Aquilops

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Aquilops
Temporal range: Early Cretaceous, 107 Ma
Holotype skull (below) with reconstruction and replica (above) as exhibited in Sam Noble Oklahoma Museum of Natural History
Scientific classification Edit this 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 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 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.

A small neoceratopsian, the only known skull of Aquilops is 84.2 mm (3.31 in) long as preserved, from which a total length of about 60 cm (24 in) and a weight of about 1.6 kg (3.5 lb) has been extrapolated. A fully grown Aquilops would probably have been 1 m (39 in) 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 tip of the rostral bone at the front of the snout is directed downwards and has a strongly arched keel with a boss at the front edge. The rostral forms a unique, concave profile in front of the upper teeth. The antorbital fenestra is unique in being twice as long as tall and in tapering to a sharp point below the orbit.

At the time it was described, Aquilops was 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 the one of the most basal 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 Cretaceous. The Himes Member of the formation which Aquilops is known from represents a braided river system.

Discovery and naming

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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.[1][2][3]

Holotype skull held by lead-describer Andrew Farke to show scale

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.[1][2] 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.[4] Wedel described his role in the project as "social glue" and drawing the skull reconstruction.[5][6][7]

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.[4] 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.[2] 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.[4][5][8]

Aquilops exhibit next to Pentaceratops skeleton at the Sam Noble Museum

The holotype 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 front end of the rostral nasal bones, the braincase, and most of the palatal bones are missing. The specimen was probably a subadult individual.[2] 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.[3][9]

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. 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 better known relatives such as Archaeoceratops and the more distantly related Psittacosaurus, since the body-plans of early ceratopsians were fairly similar.[8]

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

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.[10][11][12] Wedel noted that whatever attention Aquilops would get was probably going to be due to Engh's artwork.[5]

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."[13][14][7][15]

Description

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Skull

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Size comparison with Farke for human scale

A small neoceratopsian, the only known and presumably subadult skull of Aquilops is 84.2 mm (3.31 in) long as preserved, from the tip of the rostral bone at the front to the tip of the jugal 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 22.6 mm (0.89 in) while the preserved part of the dentary, the tooth-bearing bone of the lower jaw, is 30.3 mm (1.19 in).[2] Extrapolating from Archaeoceratops, Wedel estimated the total body length of Aquilops to have been about 60 cm (24 in) and its weight about 1.6 kg (3.5 lb) 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 1 m (39 in) or less in total length.[16] As an early ceratopsian, Aquilops would have had a large head, long hindlimbs, shorter forelimbs, a long tail, and probably been bipedal.[8]

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 lacrimal bones 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.[2]

Interpretative diagram of the skull (left) and reconstruction (right) from the side and above

The rostral bone (the frontmost bone of the snout in ceratopsians which formed the upper beak) 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 5.3 mm (0.21 in) long by 1.2 mm (0.047 in) tall. Farke noted that he did not think this feature was a displaced piece of bone or pathological 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 behind it, the rostral tip forms a nearly 90 degree angle with the line of the upper teeth of the maxilla, 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.[2][8]

Skull shown from the right and left sides (left), above, and below

The premaxilla of Aquilops is roughly triangular in side view, and its lower border is straight and contains three teeth at the back. Together, the maxilla, premaxilla and rostral form a unique, concave profile in front of the upper teeth. There is a swelling on the side of the premaxilla right above its lower margin. The external naris (bony nostril) is 9 mm (0.35 in) long as preserved, small in proportion to the orbit and the antorbital fossa, typical for neoceratopsians. The naris is angled 60 degrees to horizontal, and the preserved part of its margin indicates it was elliptical. Seen from below, the premaxilla is broadest at its midpoint, and is pinched at the front and back, where it connects with the rostral and maxilla, respectively. Taking distortion into account, the row of alveoli (tooth sockets) of the premaxilla would have been in line with those of the maxilla, and not outside the line, as is the case in other ceratopsians that have such teeth. The upper surface of the nasal bones is relatively flat and untextured, as in many other ceratopsians outside Coronosauria.[2]

Hypothetical life restoration of the head

The palpebral bone above the eye of Aquilops is broadest where it attaches with the prefontal and lacrimal bones, and tapers to a rounded profile at its outer end. Its upper surface is flattened, and overall the palpebral is similar to those of other basal neoceratopsians. The antorbital fossa (an opening in front of the eye socket) is elongated from front to back, triangular, is tallest at the front end, deepest at its hind end, and its lower border is almost horizontal. The upper edge of the fossa is sharply defined at the portion below the orbit, with a distinct bony bar, this distinction becoming less defined towards the front. The fossa is elongated compared to in other ceratopsians, its height:length ratio being 0.43, whereas it is more equal in relatives, even circular in leptoceratopsids and protoceratopsids. It is unique in being twice as long as tall and in tapering to a sharp point below the orbit.[2]

The lacrimal bone of Aquilops inserts into the jugal bone below the orbit along a V-shaped contact area, as is widespread among neoceratopsians, whereas it is fairly linear in most Psittacosaurus specimens. The prefrontal bone is roughly hatchet-shaped and narrowest at the back, where it forms the upper margin of the orbit. The frontal bones are roughly diamond-shaped in side view, with slight ridges running along the interfrontal suture, and is otherwise typical of basal ceratopsians. The postorbital bone is longer than it is tall and wide, and does not form part of the margin of the infratemporal fenestra as in other ceratopsians outside Coronosauria. The jugal bone is level along most of its side surface, apart from a prominent ridge and concavity right in front of the infratemporal fenestra. There is no visible scar from the epijugal, indicating the animal did not have such an ossification, as is also the case for non-neoceratopsians and juvenile coronosaurs such as Triceratops. The hind margin of the jugal has light neurovascular impressions rather than the more heavily sculptured surface of most other ceratopsians, and may be a juvenile feature, as it is in ceratopsids. Though its shape is obscured by crushing, the orbit appears to have been longer than tall, and was proportionally large, a juvenile feature in many vertebrates.[2]

Lower jaw from the sides, above and below (upper left), occlusal surface of the seventh maxillary tooth (upper right), and close-ups of dentition (below)

The predentary bone of Aquilops tapers to a sharp point when seen from both above and the side, in contrast to the blunt U-shape in psittacosaurids and Liaoceratops, but like other neoceratopsians. The cutting surface grades smoothly into the upper midline of the bone, where it is shallowly scooped, like in basal neoceratopsians but in contrast to the deep cavity on the midline of coronosaurs. The upper margin of the predentary is blunt in Aquilops like in other neoceratopsians, whereas it is sharp and ridge-like in more basal ceratopsians. The left and right surfaces of the predentary contact each other below along a rounded keel, unlike the broadly oval shape of more basal ceratopsians. The inner side of the dentary bone is convex at the back and concave at the front, and the Meckelian groove there is rather broad, as in other neoceratopsians. When seen from above, the tooth row of the dentary is concave to the outer side, and is greatly inset. The tooth row extends forward to the suture with the predentary, so that there was a minimal diastema (gap) at this end, typical of basal ceratopsians but unlike ceratopsids.[2]

Dentition

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The premaxilla contains three teeth that are directed vertically, and the frontmost tooth is much smaller than the two behind it. Seen from the outward side, these teeth are roughly teardrop-shaped, broadest at the base of the tooth crown, and gently taper towards the tip. The base of each premaxillary tooth crown is elongated from front to back, and the front and back edges of the crowns are marked by carinae (cutting edges). The crowns lack denticles (serrations), unlike Archaeoceratops, Liaoceratops, and Yamaceratops, and both their outward and indward surfaces bear tooth enamel. The frontmost right premaxillary tooth is slightly rounded at its tip, suggesting a wear facet, but this is not present on the second tooth, though this may be because it had recently erupted. The right maxilla contains nine densely packed teeth, separated from those of the premaxilla by a 6 mm wide diastema. The teeth positioned at the middle of the maxillary row are largest, and seen from the outer side, each tooth crown tapers towards its tip and is ovate in shape. The outwards surface of each crown is divided by a broad ridge running towards the tip, with further, less pronounced ridges next to it, as seen in Archaeoceratops and Auroraceratops, and the main ridge merges with the pronounced cingulum at the base of each tooth.[2]

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

At least three "waves" of newly erupted teeth, or Zahnreihen, are preserved in the maxilla, moving from back to front. There are at least three denticles on each of the occlusal edges of their unworn crowns. Three or four "cusps" are present on worn teeth, which are the occlusal part of the ridges on the outwards sides. Only the inwards side of the maxillary tooth crowns bear enamel, and their wear surfaces are angled to the side from the base to the tip. The left dentary preserves twelve incomplete, closely packed teeth. The major ridge on the inwards surface of each tooth crown here is placed at the middle and is more weakly developed than in the maxillary teeth. The weaker ridges on the sides end in fine denticles, and the cingula here are much less developed than in the maxillary teeth. Only the inward side of the dentary tooth crowns bear enamel. There are visible replacement teeth at two places under the functional teeth. The teeth at the front of the teeth appear to be smaller than those at the back. The dentary teeth greatly exceeding the number of maxillary teeth is a feature shared with Liaoceratops, while it is more equal in other basal neoceratopsians.[2]

Classification

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Life restoration with hypothetical body

Aquilops is a member of the group Neoceratopsia, which includes most ceratopsian dinosaurs but excludes groups like Psittacosauridae and Chaoyangsauridae. Basal neoceratopsians bear large, bony attachments for jaw muscles that later evolved into large frills. It was not until the ceratopsids, the group that includes large ceratopsians like Triceratops and Styracosaurus, that skulls evolved exaggerated horns, spikes,[2] and frills.[17] Although early neoceratopsians from Asia are well known,[2][18][19] North American neoceratopsians from the Early Cretaceous were poorly understood prior to the description of Aquilops.[20] 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. Farke and colleagues (2014) performed a cladistic analysis (a study of the evolutionary relationships of organisms) that found Aquilops as the basalmost (most "primitive") member of Neoceratopsia and outside of the Leptoceratopsidae-Coronosauria group. Other neoceratopsians in a similar grade included the Asian genera Auroraceratops, Yamaceratops. and Helioceratops. They found that a more derived position, such as in Protoceratopsidae or Leptoceratopsidae, was less likely. Although, 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 practically the same.[2]

Co-describer Mathew J. Wedel with reconstructed Aquilops skeleton at DinoCon
Holotype skull of Sasayamagnomus, a probable sister taxon of Aquilops from Japan

Later phylogenetic analyses would get similar results. In a 2018 paper on Auroraceratops, American scientist Eric M. Morschhauser and colleagues recovered Aquilops in a polytomy (unresolved relationship) with Auroraceratops and an unnamed Mongolian neoceratopsian (cataloged under specimen number ZPAL MgD 1156). However, another phylogenetic tree (a diagram illustrating the evolutionary relationships of organisms) and analysis in the same paper found Aquilops at the base of a clade containing it, ZPAL MgD 1156, and Auroraceratops. Both Aquilops and Auroraceratops have a ramus (ridge of bone) on their jugal running at the bottom of the orbit that is wider than deep.[21] Son and colleagues (2022) got a similar result, however Aquilops was more advanced than Auroraceratops and comparable to Yamaceratops and Euceratopsia.[22] A 2024 paper by Japanese paleontologist Tomonori Tanaka and colleagues found Aquilops to be the sister taxon of Sasayamagnomus from Japan, suggesting that they may have formed a group of trans-Pacific basal neoceratopsians. The placement of Aquilops according to their cladogram is shown below.[23]

Ceratopsia

Paleoenvironment

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Map of North America during the mid Albian, around the time Aquilops lived. The Bighorn Basin where its fossils are known is marked in white.

Aquilops was found in rocks assigned to Unit VII, also known as the Himes Member, of the Cloverly Formation in what is now Montana. The Himes Member is a distinct layer of brightly colored red, maroon, and orange sandstones and is the uppermost section of the formation.[2] Deposits of the Cloverly Formation range from central Wyoming into central Montana, largely within the Bighorn Basin. Many of these deposits overlay the Jurassic-aged Morrison Formation.[24] The age of the Himes Member is debated.[25][26][27] Farke and colleagues' description of Aquilops dated it to the Albian, about 109-104 million years ago.[2] However, a 2019 study by American paleontologist Michael D'Emic and colleagues revised the chronostratigraphy of the formation, estimating the actual age to be between 109-98 million years ago. This would put it in the mid–late Albian to early Cenomanian stages of the Cretaceous period.[26]

Beginning in the Late Cretaceous, North America was bisected into two major landmasses, Laramidia in the West, and Appalachia in the East, by the Western Interior Seaway.[28] though during the Albian this Seaway had not fully divided North America.[26] The environment of the Cloverly Formation is poorly understood, largely on account of its faunal composition. Potentially marine fish, such as pycnodonts, existed alongside freshwater animals, like amphibians.[29] The water was warm, with a hot season surface temperature of about 26 degrees Celsius (79 degrees Fahrenheit), while the air was about 24 degrees Celsius (75 degrees Fahrenheit).[30] During the Albian, much of North America was blanketed by vast forests composed of diverse plant life. The canopy was dominated by trees such as pines,[31] redwoods, araucarians, cheirolepidiaceans, ginkgo's,[32] yews, taxodioids, athrotaxidoids, podocarps, plane trees (sycamores),[31] magnoliales, laurales, fabids, malvids, Tempskyaceae ferns, and Cyatheales ferns.[31][33][34] The forest floor supported a rich understory of palms,[35] cycads, cycadeoids, horsetails, forked ferns, spleenworts, and Osmundaceae ferns.[33][31] More open areas would have been home to the fern Ruffordia.[31][36] Farke stated Aquilops would have been a plant-eater, using its hooked beak to nip at vegetation.[12]

Fauna

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An outcrop of the Cloverly Formation, with the Himes Member at the top in red sandstone.

Mudstones make up the lower members of the Cloverly, likely deposited by lakes or an alluvial plane. In contrast, the Himes Member is a conglomerate and sandstone formation, which was a braided river system during the Cretaceous.[24][27] These rivers were energetic[37] and flowed alongside low-energy, seasonal lakes.[27] In these water bodies lived an array of fish, such as the lungfish Ceratodus, semionotid Lepidotes, and the shark Hybodus, amphibians, including the salamander-like Albanerpeton, turtles, like Naomichelys and Glyptops, and crocodyliforms are represented by indeterminate bernissartids, atoposaurids, and goniopholidids. Microvertebrate fossils are found in the seasonal lacustrine sections, while macrovertebrate remains are often discovered in the river flow deposits.[29] The presence of turtles, lungfish, and crocodilians suggest that the Cloverly had a warm climate year-round.[25][28] Mammals and squamates (snakes and lizards) are the rarest animals known from the formation, the former represented by genera like the gobiconodontid Gobiconodon, the multituberculate Paracimexomys, and the marsupial Atokatheridium, while squamates like the paramacellodid Paramacellodus and teiid Ptilotodon have been found.[29] The faunal makeup of the Cloverly, Antlers, and Cedar Mountain Formations are very similar, with several genera represented in all three.[29]

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

Dinosaurs are the most diverse group in the Cloverly Formation, constituting about a quarter of its total vertebrate diversity.[29] Aquilops is relatively rare compared to other ornithischian dinosaurs known from the formation, as it is only known from a single specimen.[2] In contrast, the large iguanodont Tenontosaurus,[38] is represented by about 80 specimens[39] and is the most commonly known dinosaur in the formation.[20] Other ornithischians known from the formation include the thescelosaurid Zephyrosaurus[40] and the armored nodosaurid anklyosaurs Sauropelta[41][25]: 104  and Tatankacephalus.[42] The largest dinosaur known from the area is the sauropod Sauroposeidon,[43][44][45] and the sauropod Rugocaudia is also known from there.[46] Theropods of various sizes and groups are represented, such as the carcharodontosaurid Acrocanthosaurus, an apex predator,[47] the deinonychosaur Deinonychus, which predated on Tenontosaurus,[39][48][49] the oviraptorosaur Microvenator,[50] which hunted smaller prey,[28] and an indeterminate ornithomimid.[51]

Teeth of a neoceratopsian similar to and older than Aquilops from the Arundel Formation of Maryland

In 2018, the paleontologist Chase Brownstein reported neoceratopsian teeth older than Aquilops from the Arundel Formation of Maryland. This suggests there was an interchange of neoceratopsians between North America and Asia during the Aptian, and supported the idea that the group had dispersed into North America by the Aptian. The owner of the Arundel teeth would have been part of this dispersal, and probably belonged to an animal similar to Aquilops.[52] Other dinosaurs from the Cloverly Formation have been reported from the Arundel Formation as well, such as Acrocanthosaurus,[53] Deinonychus,[20][54] and Tenontosaurus, implying that there was a cross-continental distribution of these genera.[52] However, sauropod and ankylosaur fossils are much more common in Appalachian fossil formations than Laramidian ones, suggesting that they had different faunal compositions.[52][20]

See also

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References

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  1. 1 2 Crofts, Natalie (2014-12-12). "Utah paleontologist shares tale of discovering cat-sized dinosaur". KSL.com. Salt Lake City: Deseret Digital Media. Retrieved 2014-12-23.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Farke, Andrew A.; Maxwell, W. Desmond; Cifelli, Richard L.; Wedel, Mathew J. (2014-12-10). "A Ceratopsian Dinosaur from the Lower Cretaceous of Western North America, and the Biogeography of Neoceratopsia". PLoS ONE. 9 (12) e112055. Bibcode:2014PLoSO...9k2055F. doi:10.1371/journal.pone.0112055. PMC 4262212. PMID 25494182.
  3. 1 2 "Discovering Aquilops Americanus - Sam Noble Museum". 19 August 2017. Retrieved 27 August 2026.
  4. 1 2 3 Farke, Andrew (11 December 2014). "Assembling the Aquilops Paper". The Official PLOS Blog. Retrieved 27 August 2026.
  5. 1 2 3 Wedel, Matt (10 December 2014). "Please welcome Aquilops americanus". Sauropod Vertebra Picture of the Week. Retrieved 27 August 2026.
  6. ↑ "Reconstructing the skull of Aquilops". Sauropod Vertebra Picture of the Week. 11 December 2014. Retrieved 27 August 2026.
  7. 1 2 Wang, Andrew (12 July 2025). "Paleontologist's discovery appears in new 'Jurassic World' film - Silvercity Daily Press". Retrieved 27 August 2026.
  8. 1 2 3 4 Farke, Andrew (10 December 2014). "Aquilops, the little dinosaur that could". The Official PLOS Blog. Retrieved 26 August 2026.
  9. ↑ "A quick stop at the Oklahoma Museum of Natural History". Sauropod Vertebra Picture of the Week. 21 December 2016. Retrieved 27 August 2026.
  10. ↑ "Aquilops americanus: Small Cat-Sized Dinosaur Discovered in Montana | Paleontology | Sci-News.com". Sci.News: Breaking Science News. 11 December 2014. Retrieved 27 August 2026.
  11. ↑ "Oldest horned dinosaur species in North America found in Montana". Retrieved 27 August 2026.
  12. 1 2 "Newly discovered dinosaur had an eagle face, was the size of a crow". Los Angeles Times. 12 December 2014. Retrieved 27 August 2026.
  13. ↑ "Starring in Jurassic World: Rebirth, Meet the Oklahoma Museum of Natural History's Newest Celebrity: Aquilops Americanus". www.ou.edu. Retrieved 27 August 2026.
  14. ↑ Tanaka, Rodney (25 June 2025). "WesternU professor helped name dinosaur featured in Jurassic World Rebirth | WesternU News". Retrieved 27 August 2026.
  15. ↑ "Who Is Dolores? Everything to Know About Jurassic World Rebirth's Adorable Aquilops". NBC. 2 July 2025. Retrieved 27 August 2026.
  16. ↑ "How bigsmall was Aquilops?". Sauropod Vertebra Picture of the Week. 12 December 2014. Retrieved 27 August 2026.
  17. ↑ Sampson, Scott D.; Loewen, Mark A.; Farke, Andrew A.; Roberts, Eric M.; Forster, Catherine A.; Smith, Joshua A.; Titus, Alan L. (2010-09-22). "New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism". PLOS ONE. 5 (9) e12292. Public Library of Science. doi:10.1371/journal.pone.0012292. ISSN 1932-6203. PMC 2929175. PMID 20877459.
  18. ↑ Xu, Xing; Makovicky, Peter J.; Wang, Xiao-lin; Norell, Mark A.; You, Hai-lu (2002). "A ceratopsian dinosaur from China and the early evolution of Ceratopsia". Nature. 416 (6878): 314–317. doi:10.1038/416314a. ISSN 0028-0836.
  19. ↑ Xu, Xing; Forster, Catherine A; Clark, James M; Mo, Jinyou (2006-09-07). "A basal ceratopsian with transitional features from the Late Jurassic of northwestern China". Proceedings of the Royal Society B: Biological Sciences. 273 (1598): 2135–2140. doi:10.1098/rspb.2006.3566. ISSN 0962-8452. PMC 1635516. PMID 16901832.
  20. 1 2 3 4 Frederickson, Joseph A.; Lipka, Thomas R.; Cifelli, Richard L. (2018-08-28). "Faunal composition and paleoenvironment of the Arundel Clay (Potomac Formation; Early Cretaceous), Maryland, USA". Palaeontologia Electronica. doi:10.26879/847. Retrieved 2026-08-28.
  21. ↑ Morschhauser, Eric M.; You, Hailu; Li, Daqing; Dodson, Peter (2018-12-13). "Phylogenetic history of Auroraceratops rugosus (Ceratopsia: Ornithischia) from the Lower Cretaceous of Gansu Province, China". Journal of Vertebrate Paleontology. 38 (sup1). Taylor & Francis: 117–147. doi:10.1080/02724634.2018.1509866. ISSN 0272-4634.
  22. ↑ Son, M.; Lee, Y.-M.; Zorigt, B.; Kobayashi, Y.; Park, J.-Y.; Lee, S.; Kim, S.-H.; Lee, K. Y. (2022). "A new juvenile Yamaceratops (Dinosauria, Ceratopsia) from the Javkhlant Formation (Upper Cretaceous) of Mongolia". PeerJ. 10 e13176. Bibcode:2022PeerJ..1013176S. doi:10.7717/peerj.13176. PMC 8992648. PMID 35402094.
  23. ↑ Tanaka, Tomonori; Chiba, Kentaro; Ikeda, Tadahiro; Ryan, Michael J. (2024). "A new neoceratopsian (Ornithischia, Ceratopsia) from the Lower Cretaceous Ohyamashimo Formation (Albian), southwestern Japan". Papers in Palaeontology. 10 (5). doi:10.1002/spp2.1587. ISSN 2056-2799.
  24. 1 2 DeCelles, Peter G.; Burden, Elliott T. (1992). "Non-marine sedimentation in the overfilled part of the Jurassic-Cretaceous Cordilleran foreland basin: Morrison and Cloverly Formations, central Wyoming, USA". Basin Research. 4 (3–4): 291–314. Bibcode:1992BasR....4..291D. doi:10.1111/j.1365-2117.1992.tb00050.x. ISSN 1365-2117.
  25. 1 2 3 Ostrom, John Harold (1970). "Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana". Bulletin of the Peabody Museum of Natural History. 35: 1–234.
  26. 1 2 3 D'Emic, Michael D.; Foreman, Brady Z.; Jud, Nathan A.; Britt, Brooks B.; Schmitz, Mark; Crowley, James L. (2019-04-01). "Chronostratigraphic Revision of the Cloverly Formation (Lower Cretaceous, Western Interior, USA)". Bulletin of the Peabody Museum of Natural History. 60 (1): 3. Bibcode:2019BPMNH..60....3D. doi:10.3374/014.060.0101. ISSN 0079-032X.
  27. 1 2 3 Moblery, Ralph, Jr. (1960-08-01). "Morrison, Cloverly, and Sykes Mountain formations, northern Bighorn Basin, Wyoming and Montana". GSA Bulletin. 71 (8): 1137–1176. doi:10.1130/0016-7606(1960)71[1137:MCASMF]2.0.CO;2. ISSN 0016-7606.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  28. 1 2 3 Maxwell, W. Desmond. (1997). "Cloverly Formation". In Currie, Philip J.; Padian, Kevin (eds.). The Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 128–129. ISBN 978-0-12-226810-6.
  29. 1 2 3 4 5 Oreska, Matthew P. J.; Carrano, Matthew T.; Dzikiewicz, Katherine M. (2013). "Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), I: faunal composition, biogeographic relationships, and sampling". Journal of Vertebrate Paleontology. 33 (2): 264–292. Bibcode:2013JVPal..33..264O. doi:10.1080/02724634.2012.717567. ISSN 0272-4634.
  30. ↑ Allen, M. L.; Suarez, M. B.; Adams, T. L.; Suarez, C. A. (2025-05-13). "Ecohydrology and paleoenvironment of the Cretaceous (Albian) Cloverly Formation: insights from multi-taxon oxygen isotope analysis of vertebrate phosphates". Frontiers in Earth Science. 13 1497416. Frontiers. Bibcode:2025FrEaS..1397416A. doi:10.3389/feart.2025.1497416. ISSN 2296-6463.
  31. 1 2 3 4 5 Huang, Qiangsheng C.; Dilcher, David L. (1994), "Evolutionary and paleoecological implications of fossil plants from the Lower Cretaceous Cheyenne Sandstone of the Western Interior", Geological Society of America Special Papers, vol. 287, Geological Society of America, pp. 129–144, doi:10.1130/spe287-p129, ISBN 978-0-8137-2287-0, retrieved May 18, 2026
  32. ↑ LaPasha, Constantine A.; Miller, Charles N. (June 4, 1985). "Flora of the Early Cretaceous Kootenai Formation in Montana, bryophytes and tracheophytes excluding conifers". Palaeontographica Abteilung B: 111–145.
  33. 1 2 G. R. Upchurch; P. R. Crane; A. N. Drinnan (1994). "The Megaflora from the Quantico Locality (Upper Albian), Lower Cretaceous Potomac Group of Virginia". Virginia Museum of Natural History.
  34. ↑ Peppe, Daniel J.; Hickey, Leo J.; Miller, Ian M.; Green, Walton A. (October 1, 2008). "A Morphotype Catalogue, Floristic Analysis and Stratigraphic Description of the Aspen Shale Flora(Cretaceous–Albian) of Southwestern Wyoming". Bulletin of the Peabody Museum of Natural History. 49 (2): 181–208. Bibcode:2008BPMNH..49..181P. doi:10.3374/0079-032X-49.2.181. ISSN 0079-032X. Archived from the original on August 1, 2025. Retrieved September 17, 2025.
  35. ↑ Vega, Francisco J.; García-Barrera, Pedro; Perrilliat, María del Carmen; Coutiño, Marco A.; Marino-Pérez, Ricardo (January 2006). "El Espinal, a new plattenkalk facies locality from the Lower Cretaceous Sierra Madre Formation, Chiapas, southeastern Mexico". Revista Mexicana de Ciencias Geológicas. 23 (3): 323–333. ISSN 1026-8774.
  36. ↑ Mohr, Barbara A. R.; Bernardes-de-Oliveira, Mary E. C.; Loveridge, Robert; Pons, Denise; Sucerquia, Paula Andréa; Castro-Fernandes, Maria C. (May 1, 2015). "Ruffordia goeppertii (Schizaeales, Anemiaceae) – A common fern from the Lower Cretaceous Crato Formation of northeast Brazil". Cretaceous Research. 54: 17–26. Bibcode:2015CrRes..54...17M. doi:10.1016/j.cretres.2014.11.006. ISSN 0195-6671.
  37. ↑ Zaleha, Michael J.; Wiesemann, Shayne A. (2005-01-01). "Hyperconcentrated Flows and Gastroliths: Sedimentology of Diamictites and Wackes of the Upper Cloverly Formation, Lower Cretaceous, Wyoming, U.S.A.". Journal of Sedimentary Research. 75 (1): 43–54. Bibcode:2005JSedR..75...43Z. doi:10.2110/jsr.2005.005. ISSN 1938-3681.
  38. ↑ Forster, C. A. (1984). "The paleoecology of the ornithopod dinosaur Tenontosaurus tilletti from the Cloverly Formation, Big Horn Basin of Wyoming and Montana". The Mosasaur. 2: 151–163.
  39. 1 2 Nudds, John R.; Lomax, Dean R.; Tennant, Jonathan P. (2022-12-01). "Gastroliths and Deinonychus teeth associated with a skeleton of Tenontosaurus from the Cloverly Formation (Lower Cretaceous), Montana, USA". Cretaceous Research. 140 105327. Bibcode:2022CrRes.14005327N. doi:10.1016/j.cretres.2022.105327. ISSN 0195-6671.
  40. ↑ Sues, Hans-Dieter (1980). "Anatomy and relationships of a new hypsilophodontid dinosaur from the Lower Cretaceous of North America". Palaeontographica Abteilung A. 169 (1–3): 51–72.
  41. ↑ Parsons, William L.; Parsons, Kristen M. (2001). "Description of a new skull of Sauropelta cf. S. edwardsi Ostrom, 1970 (Ornithischia: Ankylosauria)". Journal of Vertebrate Paleontology. 21 (Supplement to 3 - Abstracts of Papers, 61st Annual Meeting of the Society of Vertebrate Paleontology): 87A. doi:10.1080/02724634.2001.10010852. S2CID 220414868.
  42. ↑ Parsons, William L.; Parsons, Kristen M. (2009). "A new ankylosaur (Dinosauria: Ankylosauria) from the Lower Cretaceous Cloverly Formation of central Montana". Canadian Journal of Earth Sciences. 46 (10). NRC Research Press: 721–738. Bibcode:2009CaJES..46..721S. doi:10.1139/E09-045. ISSN 0008-4077.
  43. ↑ Wedel, M.J.; Cifelli, R.L. (2005). "Sauroposeidon: Oklahoma's native giant". Oklahoma Geology Notes. 65 (2): 40–57.
  44. ↑ D'Emic, M.D.; Foreman, B.Z. (2012). "The beginning of the sauropod dinosaur hiatus in North America: insights from the Lower Cretaceous Cloverly Formation of Wyoming". Journal of Vertebrate Paleontology. 32 (4): 883–902. Bibcode:2012JVPal..32..883D. doi:10.1080/02724634.2012.671204. S2CID 128486488.
  45. ↑ D'Emic, Michael D.; Melstrom, Keegan M.; Eddy, Drew R. (2012-05-15). "Paleobiology and geographic range of the large-bodied Cretaceous theropod dinosaur Acrocanthosaurus atokensis". Palaeogeography, Palaeoclimatology, Palaeoecology. 333–334: 13–23. Bibcode:2012PPP...333...13D. doi:10.1016/j.palaeo.2012.03.003. ISSN 0031-0182.
  46. ↑ Woodruff, D. Cary (2012-08-01). "A new titanosauriform from the Early Cretaceous Cloverly Formation of Montana". Cretaceous Research. 36: 58–66. Bibcode:2012CrRes..36...58W. doi:10.1016/j.cretres.2012.02.003. ISSN 0195-6671.
  47. ↑ D'Emic, Michael D.; Melstrom, Keegan M.; Eddy, Drew R. (2012). "Paleobiology and geographic range of the large-bodied Cretaceous theropod dinosaur Acrocanthosaurus atokensis". Palaeogeography, Palaeoclimatology, Palaeoecology. 333–334: 13–23. Bibcode:2012PPP...333...13D. doi:10.1016/j.palaeo.2012.03.003.
  48. ↑ Gignac, P.M.; Makovicky, P.J.; Erickson, G.M.; Walsh, R.P. (2010). "A description of Deinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations". Journal of Vertebrate Paleontology. 30 (4): 1169–1177. Bibcode:2010JVPal..30.1169G. doi:10.1080/02724634.2010.483535. S2CID 86182457.
  49. ↑ Frederickson, J. A.; Engel, M. H.; Cifelli, R. L. (August 15, 2020). "Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis". Palaeogeography, Palaeoclimatology, Palaeoecology. 552 109780: 4–7. Bibcode:2020PPP...55209780F. doi:10.1016/j.palaeo.2020.109780. S2CID 219059665.
  50. ↑ Makovicky, Peter J.; Sues, Hans-Dieter (1998). "Anatomy and phylogenetic relationships of the theropod dinosaur Microvenator celer from the Lower Cretaceous of Montana". American Museum Novitates (3240). hdl:2246/3239.
  51. ↑ Hunt, Rebecca K.; Quinn, James H. (2018-01-02). "A new ornithomimosaur from the Lower Cretaceous Trinity Group of Arkansas". Journal of Vertebrate Paleontology. 38 (1) e1421209. Taylor & Francis. Bibcode:2018JVPal..38E1209H. doi:10.1080/02724634.2017.1421209. ISSN 0272-4634.
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  53. ↑ Carrano, Matthew T. (2024-05-01). "First definitive record of Acrocanthosaurus (Theropoda: Carcharodontosauridae) in the Lower Cretaceous of eastern North America". Cretaceous Research. 157 105814. Bibcode:2024CrRes.15705814C. doi:10.1016/j.cretres.2023.105814. ISSN 0195-6671.
  54. ↑ Brownstein, Chase Doran (2017-03-08). "Description of Arundel Clay ornithomimosaur material and a reinterpretation of Nedcolbertia justinhofmanni as an "Ostrich Dinosaur": biogeographic implications". PeerJ. 5 e3110. Bibcode:2017PeerJ...5e3110B. doi:10.7717/peerj.3110. ISSN 2167-8359. PMC 5345386. PMID 28286718.
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