Gaining infamy in the wake of the film Jurassic Park because it justified the exaggerated size of its Velociraptor characters, this Utah original remains the largest dromaeosaur known to science even after more than thirty years of unprecedented numbers of new discoveries of dinosaur species. Three other ‘raptors in its general size range have been named—all of which have sculptures representing them at the Park—and at least four other fragmentary, unnamed species appear to approach its size as well. Though its record of gigantism remains unimpeached, our image of this animal has changed significantly since its initial discovery thanks to continuous recovery of new Utahraptor specimens and helpful evidence provided by discoveries of its closest relatives among the ‘raptor clan.

• Some Utahraptor aficionados may question my claim that its status as largest known dromaeosaur has not yet been surpassed, and rightfully so. I’ll stick to my guns here with a little more explanation. Five years after its description, the discovery of Megaraptor in Argentina apparently deposed Utahraptor from its BIGGEST EVAR status. However, subsequent studies found that Megaraptor turned out to belong to a different theropod group altogether. Scientists placed it among the ‘raptors in part because its purported toe claw sported an asymmetrical set of blood grooves similar to those which characterize dromaeosaurs; later discoveries clarified that this apparent toe claw belonged on Megaraptor’s hand instead. Currently, an isolated toe bone from Uzbekistan could indicate a dromaeosaur larger than Utahraptor roamed those lands at roughly the same time as the infamous Ulughbegsaurus erroneously reported to have outweighed Tyrannosaurus rex by orders of magnitude (more on that story here). I don’t currently have access to its description, but even without it, two factors complicate that claim. First, any size estimate based on a single bone is fraught with potential complications that limit its reliability, such as individual proportions or proportional differences between species, misidentification of the bone (which I am not claiming or denying happened in this case—I simply have no data and find myself forced to apply general rules for the time being), and the usual factors which complicate size estimates even for complete dinosaur skeletons such as soft tissue reconstruction or the misapplication of estimation methods. Second, BYU has uncovered fragmentary Utahraptor material which suggests an unusual size for one individual: estimates based on this material overlap with Allosaurus in size, with length estimated at nearly 30 feet. Does the claim of the Uzbekistani dromaeosaur take this giant Utahraptor into account? If so, can estimates as loose as these necessarily are be trusted enough to state with confidence, especially in light of the record’s previous false breaking? For these reasons, I emphasize that Utahraptor remains the largest dromaeosaurid KNOWN to science because it has enough material to justify at least a conservative range of sizes—that is to say, it’s the largest knowable or named dromaeosaur at this point. If I can get my hands on Sues et al 2023 and look at their reasoning in detail, I may update this section to reflect their findings.
• One more technical note: some readers may be wondering why the title of this post refers to Utahraptor ostrommaysi and not ostrommaysorum. Well, papers referring to this taxon seem equally confused as to which is correct, siding with one or the other usually without explanation, even in subsequent papers by the authors of the original species description. Ostrommaysorum is a later name which one checklist of dinosaur names, Olshevsky 2000, explains as an attempt to correct an issue with grammar: the species name honors John Ostrom and Chris Mays, and so it should use the plural suffix -orum instead of the singular suffix -i. However, in 2019 Costa and Normand, writing on behalf of the ICZN organization which manages such cases of taxonomic confusion, point out that since these two names were combined into a neologism representing what the ICZN code calls “an arbitrary combination of letters,” and not a proper name, ostrommaysi does not require grammatical correction and has precedent as the first name published.
• It’s not just that Utahraptor grew large in length or weight—it also sported a heavy build. In some ways, its skull resembled that of a small tyrannosaurid like Albertosaurus, suggesting a brute force approach to dispatching prey broadly similar to that of tyrannosaurids. It may even have played an apex predator role in its ecology. However, the tip of its jaw exhibits a slight downturn similar to that seen in its relative Microraptor and to a greater extreme in the ceratosaur Masiakasaurus. This particular jaw design sets the front teeth at odd angles to each other, making them more capable of catching and holding small, slippery prey. Stomach contents for Microraptor show it preferred fish but also took small lizards, birds, and mammals as significant parts of its diet. In Utahraptor, this jaw shape correlates with unusually large vascular foramina on its chin which may indicate the area had more nerve endings and was therefore unusually sensitive. Taking these points together with a little speculation, Utahraptor may have taken large prey as a rule, but perhaps it also subsisted on small prey like lizards or salamanders for significant lengths of time, not unlike how modern wolves in the arctic include both moose and beaver in their diets depending on prey availability. If so, perhaps a sensitive chin helped Utahraptordetect prey in burrows, but take that as pure speculation. Considering the general trend toward increasingly xeric (desert) conditions throughout the Early Cretaceous of Utah, a large predator like Utahraptor may have needed to diversify its diet in order to survive.
• Early descriptions of Utahraptor, including the fictional depiction in Raptor Red, implied that it may have owed its gigantism to the extinction of the area’s allosaurs and megalosaurs at the end of the Jurassic. However, a study published last month found large allosauroid teeth across the Yellow Cat Member of the Cedar Mountain Formation, including Utahraptor territory. This confirms that allosauroids remained a presence in Utah during Utahraptor’s life and times, further complicating questions of its ecological role and evolutionary development.
• An unusually large 9-ton megablock preserving over a dozen Utahraptor skeletons currently resides at the Utah Geological Survey. It provides a wealth of scientific evidence, and has therefore received unusual scrutiny in preserving its every detail, including slow preparation, photogrammetry, detailed mapping, and thousands of photographs. Scientists hypothesize that the block preserves a void collapse in a river delta which sucked the animals down to their doom, sort of like insta-quicksand. As a result, the block preserves both juveniles and at least one adult, providing what may be a first glimpse at how ‘raptors grew up.
• The importance of Utahraptor to modern paleontology in the state has led the state government to take steps to publicize and help preserve the potential for further discoveries. In 2018, the state legislature named Utahraptor as state dinosaur, joining the state fossil, Allosaurus, as another dinosaurian symbol of the state. In 2021, the state created Utahraptor State Park just west of Arches National Park, preserving an area from which about 5,500 of an estimated potential 100,000 bones have been collected over 45 years of exploring the area.
• As stated before, Utahraptor holds an interesting relationship with the film Jurassic Park. Contrary to popular belief, though, it did not inspire the Velociraptor characters as portrayed in that movie. Its discovery postdates pre-production of the film which visualized its Velociraptors as oversized Deinonychus. Fans of the film series often debate the “true identity” of those characters, and the veracity of their theories depend largely on how they define what should be meant by their true identity. Suffice it to say that the film ‘raptors are entirely fictional. Naturally, they take the novel’s Velociraptors as a basis, which it states directly conform to the Velociraptorantirrhopus of Greg Paul’s book Predatory Dinosaurs of the World. Neither the ICZN nor paleontologists at large accepted this combination, and Paul himself eventually abandoned it, seeing as how it took as its basis a misinterpretation of Deinonychus antirrhopus’ skull. Readers of the novel can’t chalk the novel’s identification as a mistake on the part of Jurassic Park’s geneticists because the Alan Grant character refers to it as a valid taxon and an identification of skeletons he had previously excavated. Even considering the question within the novel’s milieu, since the results of Jurassic Park’s cloning are recreations of dinosaurs made without a complete understanding of how to get them right, which the novel describes in painstaking detail, they count as living paleoart and not as valid dinosaur taxa—even in the novel, they are all fictional dinosaurs. At any rate, none of them could be Utahraptor, considering how this taxon didn’t formally exist until more than a week after the movie’s release.
• If you want to count the toyline accompanying the original movie as a source for resolving this fan debate, it does include Utahraptor as a separate mold from the Velociraptors. It looks appreciably bigger than the Velociraptor toys. Yes, the toy makers would have needed to know about Utahraptor well in advance of its publication in order to produce the toy, but that just makes it the nomen nudum version, no closer to the official taxon than its physical appearance to the holotype fossils. Okay, so I’m a fanboy—sue me!
• Incidentally, Jim Kirkland considered naming the species Utahraptor spielbergi after Stephen Spielberg, the director of the first film, if they would help fund the study. He never heard back from them, and so named it after John Ostrom, the describer of Deinonychus and a prominent force in the Dinosaur Renaissance, and Chris Mays, President of Dinamation International Corporation and a backer of the research.
• At one time, the Park featured no fewer than four representations of Utahraptor, all sculpted differently yet marked with the same color scheme. In 2018, three of those sculptures received modifications reflecting the discovery of several dromaeosaur species which preserved their feathery pelage. While only one of these species, Dakotaraptor, preserved direct evidence of feathers in the form of quill knobs on its ulnae, the breadth of fossil evidence across the family including both large and small, airborne and ground bound, makes a covering of feather the “null hypothesis” or default position for any dromaeosaur at this time. With that, bear in mind that the details of their plumage and potential variations among taxa remain poorly known for the group as a whole, including Utahraptor: we may have better reason to say that it had feathers than otherwise, but we still don’t know what its feathers would have looked like. Hopefully the excellent preservation of the fossils found in the aforementioned megablock will yield some clues. The plumage added to the Austroraptor, Achillobator, and Dakotaraptor statues are therefore largely but not unreasonably speculative. The original Utahraptor statue did not receive such an upgrade in anticipation of a companion sculpture meant to show the 2020 version of Utahraptor as an illustration of how much scientists have learned in the quarter century (at the time) since its discovery. Sadly, the COVID pandemic put that project on indefinite hold due to a lack of funding, but we hope to revisit it at some point. Meanwhile, the current color scheme of the old scaly model is meant to reference both the Velociraptors of the original movie and the Blue character from Jurassic World; given how she’s not exactly blue, we’ve nicknamed our sculpture Aqua instead.

—Jeff Bond

F. E. Novas. 1998. Megaraptor namunhuaiquii, gen. et sp. nov., a large-clawed, Late Cretaceous theropod from Patagonia. Journal of Vertebrate Paleontology 18(1):4-9

Sues, H. D., Averianov, A., & Britt, B. B. (2023). A giant dromaeosaurid theropod from the Upper Cretaceous (Turonian) Bissekty Formation of Uzbekistan and the status of Ulughbegsaurus uzbekistanensis. Geological Magazine, 160(2), 355-360.

Olshevsky G (2000) An annotated checklist of the dinosaur species by continent. Mesozoic Meanderings 3, 157 pp.

Costa, T. V. V., & Normand, D. (2019). Commentaries on different uses of the specific epithet of the large dromaeosaurid Utahraptor Kirkland et al., 1993 (Dinosauria, Theropoda). The Bulletin of Zoological Nomenclature, 76(1), 90-96.

https://www.iczn.org/httpswww-iczn-orgnomenclatural-notesstagestage/keyword/25

Oswald, T., Boisvert, C., D’amore, D., & Curtice, B. (2025). “Here be Dragons”: Shed Teeth Potentially Indicate the Presence of Multiple Unidentified Allosauroids from the Early Cretaceous Cedar Mountain Formation of Utah. Journal of the Arizona-Nevada Academy of Science, 50(2), 55-129.

https://geology.utah.gov/popular/dinosaurs-fossils/megablock/

https://stateparks.utah.gov/parks/utahraptor/history/

Crichton, M. (1990). Jurassic Park. Knopf.

J. I. Kirkland, D. Burge, and R. Gaston. 1993. A large dromaeosaur (Theropoda) from the Lower Cretaceous of eastern Utah. Hunteria 2(10):1-16