Utahraptor: A History

The reconstructed skull of Utahraptor, on display in Brigham Young University’s Museum of Paleontology. Photo by Jaren Wilkey of Brigham Young University (January 26, 2018). Creative Commons Attribution-Share Alike 4.0 International license.
https://commons.wikimedia.org/wiki/File:BYU_Utahraptor_skull.jpg.

Introduction

Within the American West, you don’t need to travel far until you hit “dinosaur country”, where weathering and erosion have exposed layers of rock dated to the Mesozoic Era, and where dinosaur bones can be found sticking out of the ground. However the Mesozoic Era, the Age of Dinosaurs, spanned a very long time – about 185 million years’ worth of time! Depending on where you’re fossil hunting, different sections of that time scale are visible, and some have been more heavily studied than others.

Within North America, the three geological times which have been the focus of the majority of paleontologists’ attention have been the late Triassic, late Jurassic, and late Cretaceous Periods. It is during the late Triassic that we find creatures like the meat-eating dinosaur Coelophysis (my personal favorite), the giant rauisuchian Postosuchus, the armored aetosaur Desmatosuchus, the cow-sized dicynodont Placerias, and the crocodile-like phytosaur Rutiodon. It is within the rocks of the late Jurassic Period that we find the Morrison Formation, home to iconic Jurassic dinosaurs that every kindergartner knows by heart: Allosaurus, Brachiosaurus, Ceratosaurus, Stegosaurus, Diplodocus, and so many others. Within the rocks of the late Cretaceous Period are also found some of the most famous dinosaurs in the world, such as Albertosaurus, Centrosaurus, Styracosaurus, Parasaurolophus, Triceratops, and Tyrannosaurus.

However, these are just three thin slices of a very large cake, and there are unfortunately other time spans which haven’t received as much academic attention and where our understanding of Mesozoic life is comparatively sparser. Among these lesser-known areas is the early Cretaceous Period, which spans from 144 to about 120 million years ago. For a while, early Cretaceous rocks within North America received very little attention from either professional scholars or paleo-enthusiasts, partly due to the fact that it was overshadowed by the earlier and more famous late Jurassic Period, and partly due to the fact that exposed rock layers dated to the early Cretaceous within North America are rather hard to find.

However, one place where the rocks from this time can tell their story is eastern Utah. It is here that we find the Cedar Mountain Formation, a geological formation which spans the early and middle Cretaceous Period. It is within these rocks that some incredible discoveries have been made within the past thirty years. Among these was a predator that surely was the stuff of nightmares: Utahraptor. Measuring 7 feet tall, 20 feet long, weighing a thousand pounds, and sporting a pair of huge claws on its feet the size of your hand, it was surely the top predator of its time. Since its discovery in the early 1990s, it has taken the world by storm, but just exactly how much do we really know about it?

Raptors

The story of Utahraptor arguably begins in 1914. That year, Barnum Brown, a paleontologist working for the American Museum of Natural History in New York City, was prospecting for fossils in Alberta, Canada in rocks dated to the Campanian Stage of the late Cretaceous Period, about 80-75 MYA. There, he discovered the remains of a small meat-eating dinosaur. Eight years later in 1922, these fossils were officially named Dromaeosaurus, “the running lizard”. The creature was estimated to have measured only 6 feet long, very small as far as meat-eating dinosaurs go, but its discovery was momentous. This was the first “raptor” dinosaur that had been found (1).

Thanks to the book and the movie Jurassic Park, everybody knows what a raptor is. They were small, swift, and possibly intelligent predators with a massive hook-shaped claw on each of their feet. Moreover, thanks to discoveries made in the late 1990s and throughout the 2000s, we now know that all of these very bird-like meat-eating dinosaurs were covered in feathers. In fact, analysis shows that these creatures are as close as possible to birds without actually being birds.

Velociraptor, from the movie Jurassic Park (1993)…except that the real Velociraptor was only one-third the size, it had a long narrow skull, and it was covered in feathers.

Dromaeosaurus was the first raptor to make its presence known to the scientific community. Throughout the remainder of the 20th Century, other names would be added onto the “dromaeosaurid” family tree, names including Velociraptor (1924) and Deinonychus (1969). These were all impressive and noteworthy, but these creatures had one thing in common – they were all small. Deinonychus was the largest raptor which had been found to date, but it only measured 3 feet tall and 10 feet long. So far, nobody had found a big raptor.

That was about to change.

Discovery: The Dalton Wells Quarry

The first hint that some hitherto unknown beast had roamed Utah during the early Cretaceous Period 135 million years ago was uncovered during the mid 1970s at a site in eastern Utah called “Dalton Wells”. The place was named after the Dalton family who formerly owned the property, and which was located approximately 12.5 miles (20 km) northwest of the town of Moab, Utah. For many years, Dalton Wells had been known to the local residents as a place where fossils could be found. In fact, during the early 1960s, one J. L. Kay showed the site to Jim Jensen, a paleontologist from Brigham Young University. However, there seemed to be little interest in examining the site further, possibly because it was originally believed that the rocks were dated to the Morrison Formation of the late Jurassic Period, which was already well-studied, and not the Cedar Mountain Formation which occurs later (2).

The “Cedar Mountain Formation” was first identified in 1949 and dates to the early to middle Cretaceous Period, spanning about 144 to 95 million years ago. It unconformably overlies the Morrison Formation of the late Jurassic Period and it unconformably underlies the Naturita Formation of the middle Cretaceous. It’s the Cedar Mountain Formation which provides our clearest understanding of what prehistoric life was like in North America following the end of the Jurassic Period. This formation is divided into several geological units called “members”. Unfortunately, the same members are not present throughout the entirety of the Cedar Mountain Formation’s geographic range; different members are visible in different areas of the formation. The complete list of geological members are, listed from lowest/oldest to highest/newest with approximate dates: the Buckhorn Conglomerate (ca. 144-140 MYA), the Yellow Cat Member (139-132 MYA), the Poison Strip Member (131-119 MYA), the Ruby Ranch Member (118-105 MYA), the Short Canyon Member (104-98 MYA), and the Mussentuchit Member (97-95 MYA). The Yellow Cat Member is further sub-divided into “lower” and “upper” layers due to the presence of a “cap rock” of carbonate-rich calcrete dated to 136 MYA which divides the member in half. It is uncertain at the time of this article if these two sub-layers of the Yellow Cat Member are going to be re-classified as two separate members at some point in the future (3).

Geochronology of the members of the Cedar Mountain Formation, based on dates given in Kirkland et al (2016), Joeckel et al (2019), and Phillips et al (2021).

In 1968, Lynn Ottinger, the owner of the Moab Rock Shop, was prospecting for fossils at Dalton Wells. There, within mudstone dated to the Valanginian Stage of the early Cretaceous Period (about 135 MYA), he uncovered something interesting – a piece of a jawbone with two teeth sticking out of it. The teeth themselves looked like they belonged to a plant-eating dinosaur. Peter Galton and Jim Jensen of Brigham Young University examined this curious bone and determined that it was a piece of the right maxilla (a bone which forms part of the upper jaw) of an iguanodontid dinosaur – the first time that such a creature had been found in North America. Since iguanodonts were not known to have lived during the Jurassic Period, the rocks where the jawbone had been discovered were tentatively identified as being dated to the early Cretaceous. In 1973, Jim Jensen took some rock samples from the Dalton Wells site and confirmed that they were indeed early Cretaceous strata. In 1975, a scientific paper was published which identified the partial maxilla as belonging to an iguanodontid dinosaur. That same year, Jim Jensen and Kenneth Stadtman excavated the site for five days in the Summer to see if they could find any more fossil remains, and a second excavation was carried out in 1978. In total, about 800 specimens were gathered during these two excavations, but only a small number of them have been prepared and studied. They are currently housed in the collections of Brigham Young University (4).

The fossils which were collected from Dalton Wells in 1975 and 1978 were indeed fascinating, for they hinted at an entire dinosaurian ecosystem that no scholar had ever knew existed. They included a sauropod, an iguanodont, a nodosaur, and a large theropod. However, of the hundreds of specimens which were excavated at Dalton Wells during the 1970s, a few stood out. These include two hand claws, both of which only preserved the proximal halves which attached to the knuckles (collection ID codes: BYU 13068 and 9438) and three tail vertebrae (BYU 9429, 9435, and 9436) The two claws in particular were intriguing, but no further attention was given to them…until the early 1990s (5).

The Big Find: The Gaston Quarry

In 1989, Jim Kirkland, a paleontologist who worked for an educational company called Dinamation International, was on a fossil prospecting trip in eastern Utah. One day, he paid a visit to the Moab Rock Shop – the same place where Lynn Ottinger worked and who had discovered that fragmentary iguanodont jaw in 1968 – and saw something which took his breath away. On display in a glass case was a massive 250-pound block of stone which contained the armored back plates of an ankylosaurian dinosaur. Jim Kirkland had a particular love for ankylosaurs, so he became extremely excited when he saw this. The rock shop owner showed Kirkland where he had found the fossils – a hillside located north of Arches National Park – and Kirkland decided that he needed to launch an expedition there as soon as possible (6).

The following year in the Summer of 1990, a joint venture carried out by the College of Eastern Utah (CEU) and Dinamation International was prospecting for fossils in the area where the remains of the armored dinosaur had been discovered earlier. The goal of the expedition was to see if they could find any more remains of this tantalizing creature. One of the team members named Robert Gaston, a volunteer rock-hound from Albuquerque, arrived at the dig site where the ankylosaur osteoderms had been discovered, and he found even more bones. The dig-site was named “Gaston Quarry” in his honor. The rock layers of the quarry were dated to the upper part of the Yellow Cat Member of the Cedar Mountain Formation, 135-132 MYA, and consisted of inter-bedded limestone and siltstone, which was explained as being probably caused by sequences of floods on the edge of a lake. In total, hundreds of bones from at least six skeletons of the armored dinosaur Gastonia were discovered, but the most impressive discovery was yet to come (7).

The dig team returned to Gaston Quarry in 1991 and 1992. In October of 1991, a remarkable find was made when Carl Limoni, a laboratory staff member from the College of Eastern Utah unearthed a gigantic hooked claw. It was identified as being the large sickle claw from the foot of a raptor dinosaur…except that this one was twice the size of any other raptor claw which was known. Jim Kirkland knew right away that this was a very important find (8).

The sickle claw of Utahraptor found at Gaston Quarry in October 1991, here seen in-situ within the rock before it was excavated. Photo courtesy of Dr. James I. Kirkland, image used with permission.

At a meeting of the Society of Vertebrate Paleontology in San Diego, California from October 24-26, 1991, Jim Kirkland showed the claw which had been found to Prof. John Ostrom, who had discovered and named Deinonychus in the 1960s. Ostrom was immediately enthralled with the discovery, and with the excitement of a child began exclaiming what an amazing find this was (9).

It seemed clear that this creature simply wasn’t an unusually large Deinonychus. Not only was the claw that had been found at Gaston Quarry twice the size of any Deinonychus claw, but it had a less-pronounced curvature. Other bones which were being pulled out of the ground seemed to confirm that this was a different animal – the bones were bigger, bulkier, and more massive than the thin gracile bones of other raptors (10). So, this was a new creature, and it needed a new name. During an afternoon in January 1992, the paleontologist Robert Bakker was talking on the phone with Jim Kirkland concerning this discovery when Bakker offered a suggestion: “Why don’t you call her Utahraptor?” (11).

Later that year, it was publicly announced that a large raptor dinosaur had been discovered in eastern Utah. The news garnered a lot of media attention in the subsequent months. It even made the front page of the July 21, 1992 issue of the “Science Times” section of The New York Times. It was in this article that the name “Utahraptor” appeared in print for the first time, and also showed the first-ever image of what this animal might have looked like (12). Other newspapers across the country quickly picked up the story. The January 1993 issue of Discover magazine referred to the creature as “Utah’s Sickle-Clawed Killer” and acclaimed it as one of the top 50 scientific discoveries of the previous year. Discover magazine boldly proclaimed 1992 as the “Year of the Dinosaur” (13).

The front page of the “Science Times” section of The New York Times, dated to July 21, 1992. This article is the first time that the name “Utahraptor” appears, and the illustration accompanying it is the first published image of this animal.

The front cover of the January 1993 issue of Discover magazine, detailing the top 50 scientific discoveries made during the previous year. Evidently, the discovery of Utahraptor was deemed the most important.

In the Summer of 1993, the same time that Jurassic Park was released in movie theaters, a scientific paper written by Jim Kirkland, Donald Burge, and Robert Gaston was published in which the creature was officially named Utahraptor ostrommaysi, “John Ostrom and Chris Mays’ robber from Utah”, named in honor of Prof. John Ostrom and Chris Mays, the head of Dinamation International. In 1996, the spelling of the species name was altered to ostrommaysorum, which was the correct use of Latin grammar (14).

For Jim Kirkland, Utahraptor’s discovery had immense personal significance. He acknowledged that the discovery and naming of Utahraptor essentially made his career and solidified his reputation within scientific circles. For this discovery, he was appointed by the Utah state government as the official state paleontologist (15).

Description

The Utahraptor specimen which had been excavated at Gaston Quarry in 1991 was known from only fragmentary remains, consisting of the premaxilla (the front end of the upper jaw), the lacrimal bone (which forms the front of the eye socket), a tibia, and one sickle claw from the foot (16).

In addition to the fossils which had been found at Gaston Quarry during the early 90s, it was decided by Jim Kirkland and his colleagues that the two partial hand claws and the three tail vertebrae which had been found at Dalton Wells in the 1970s also belonged to Utahraptor and were officially listed as “referred specimens” (17).

Although it wasn’t much to go on, it was sufficient enough to warrant its classification as a new genus, and not simply an unusually large Deinonychus as some people had suggested at the time. In the 1993 article, Jim Kirkland and his colleagues summed up what made Utahraptor distinct from its more well-known relative as follows: “Utahraptor differs from Deinonychus in having a larger size, extremely blade-like manual claws, and [a] distinctive lachrymal (sic) that is subrectangular in dorsal view…Claws on the hand [are] more specialized as cutting blades than in other dromaeosaurs. Lachrymal (sic) has distinctly parallel mesial and outer sides giving it an elongate subrectangular appearance in top view” (18). The large foot claw which had been found by lab technician Carl Limoni in October 1991 was designated as the “holotype” specimen and is housed within the collections of Utah State University Eastern, formerly known as the College of Eastern Utah (CEU) (collection ID code: CEU 184v.86) (19).

An interesting point that the paleontologists studying the bones took note of were the size and proportion of the tibia. It had been expected that the bones would simply be proportionally-enlarged versions of the leg bones of other raptors, being long and thin overall, with a short femur and a longer tibia and fibula. However, the paleontologists were surprised to see that the limb bones of Utahraptor did not line up with their expectations. The tibia was very thick and robustly-built, which indicated that Utahraptor was not as swift as its smaller relatives. However, what it lacked in speed, it made up for in muscle power (20).

Utahraptor size comparison, shown as measuring 23 feet (7 meters) long compared to a 6 foot (1.8 meter) tall man. Based on the specimen BYU VP 15465. Illustration by PaleoNeolitic (November 4, 2019). Public domain image, Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Utahraptor_size.png.

There is some dispute as to exactly how big Utahraptor could get. The most common size that you will see reported in a variety of media is that it reached around 20 feet long. However, other people are not so sure. They claim that the size estimates are far too large, and that the creature actually reached around 15 feet long. Estimating size and physical proportions was difficult because we only had very fragmentary remains belonging to two individuals.

But then a few years later, paleontologists returned to Dalton Wells, and it was here that a massive cache of dinosaur fossils was uncovered, including bones from Utahraptor.

Further Fossil Finds: The Return to Dalton Wells

It had been at Dalton Wells that the first evidence of Utahraptor’s existence had been uncovered during the 1970s, but since then, the site had remained unexplored. Then in 1994, a team of paleontologists and geologists from Brigham Young University (BYU) and the Museum of Western Colorado (MWC) undertook a systematic collection of specimens from the Dalton Wells Quarry. The initial intention was to look for sauropod and iguanodont fossils, but they quickly got more than what they had bargained for. In total, the site covered about 4,000 square meters in area, far too large to excavate within a single dig season. Only 180 square meters were excavated, but even so, the payoff was stupendous. The earlier digs which had been conducted in 1975 and 1978 produced about 800 fossil specimens, but in 1994 the excavators hit a fossil bonanza. Within the 180-meter area that they dug, over 5,000 bones (either whole or in fragments) were unearthed belonging to at least nine different species of dinosaurs and four species of other animals, making it one of the richest concentrations of fossil bones anywhere in the American West (21).

The Dalton Wells dinosaur quarry, located upon a prominent spur of high ground approximately 12.5 miles northwest of the town of Moab, Utah, within land owned by the Utah state government. A: Location map for quarry and measured stratigraphic section. Topographic map from United States Geological Survey Merrimac Butte 7.5 minute quadrangle, 1985 with UTM coordinates. B: Photograph of quarry’s west excavation circa 1995, looking east. From Britt, Brooks B.; Eberth, David A.; Scheetz, Rod D.; Greenhalgh, Brent W.; Stadtman, Kenneth L. (2009). “Taphonomy of debris-flow hosted dinosaur bonebeds at Dalton Wells, Utah (Lower Cretaceous, Cedar Mountain Formation, USA)”. Palaeogeography, Palaeoclimatology, Palaeoecology, volume 280 (June 2009). Page 2.

The Dalton Wells Quarry consisted of a stacked succession of four debris flows, likely caused by flash floods, measuring two meters thick. During the early Cretaceous Period, eastern Utah lay to the east of a range of mountains known as the Cordilleran Highlands. The debris flows which were uncovered at the Dalton Wells Quarry originated somewhere west of the quarry’s location, at an undetermined distance up-slope, and the flows travelled downstream in a west-to-east direction, carrying the fossil bones from their original location and depositing them a short distance further downstream in an area of lakes and marshy wetlands (22).

For several years, dig teams returned to Dalton Wells to carry on the daunting work of cataloging and collecting bone fragments, many of which measured no larger than the size of a marble. With each subsequent excavation, the number of bone fragments increased and the number of potential individuals increased. Most of the fossils belonged to sauropods, but other fossils which were unearthed belonged to iguanodonts, the nodosaur Gastonia, the primitive ornithomimosaur Nedcolbertia, and to Utahraptor. In a report dated to 2009, it was stated that 62 teeth and 146 bones from Utahraptor had been uncovered so far belonging to at least nine individuals, which were provisionally identified as two adults, three sub-adults, and four juveniles. The fossils are currently housed within the collections of Brigham Young University (23). Considering the immense number of fossils which have been unearthed at Dalton Wells, which are still undergoing preparation and analysis after almost thirty years, there are likely many more still encased within the matrix that haven’t been seen yet.

Finding the partial remains of nine skeletons of various ages from the same species in the same location would be a landmark discovery in itself and would make any paleontologist’s career. But even the remarkable finds at Dalton Wells which were made in the middle 1990s have been dwarfed by yet another astounding discovery which was made in the early 2000s.

The Utahraptor Motherlode: The Stikes Quarry

In 2001, Matthew Stikes, a geology graduate student from Northwest Arizona University, was doing field research on the sedimentology of the Cedar Mountain Formation. He had been sent there by his teacher, Dr. Jim Kirkland, to examine the rock layers of the Poison Strip Member, and told him to be on the lookout for any bones that he might find there. As he arrived at a steep ridge overlooking Arches National Park, he spotted a small thin bone sticking out of the ground. At first, he thought that it looked like a human arm bone. Could it possibly be Stone Age remains? Well, not quite. When Matthew Stikes at last turned in his Master’s thesis, his thesis advisor Dr. Kirkland inquired if he had seen any bones while he was out there, and it was then that Stikes informed Jim Kirkland and Scott Madsen about what he had found. The two of them knew right away what it was – the limb bone of a theropod dinosaur (24).

However, the site wasn’t surveyed until four years later in 2005 when Scott Madsen, Don DeBlieux, and Jim Kirkland arrived and examined the site with their own eyes. The spot where Matthew Stikes had found this curious limb bone proved somewhat difficult to find – it took Madsen, DeBlieux, and Kirkland four hours to locate it. This was partly because the color of the bone was almost indistinguishable from the color of the surrounding rock. It was then that they found the bone that Matthew Stikes had seen, which was identified as part of a foot of a theropod dinosaur. The rock layer that the bone was found in was not dated to the Poison Strip Member, but to the earlier Yellow Cat Member. One of the first rocks that Kirkland split open contained a claw and the front end of the lower jaw of a juvenile Utahraptor. This find in itself was sufficient to warrant further examination of this site, and further digging uncovered even more bones nearby, also probably belonging to Utahraptor. This was a major discovery, and it needed to be looked at in more detail. The locality was christened “Stikes Quarry” in honor of its discoverer (25).

Jim Kirkland holding the front of the lower jaw of a juvenile Utahraptor, which he found in 2005. Utah Geological Survey. “Utahraptor Megablock Fossil Project”.
https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/megablock/.

While Jim Kirkland and other members of the Utah Geological Survey did a quick site inspection, that was really all that they could do at that juncture. The Utah Geological Survey was busy working on many other projects during that time, including a massive quarry chock-full of Falcarius skeletons, and couldn’t add another dig-job onto their already daunting work list, so it could not conduct an excavation of Stikes Quarry. Therefore, they contacted Washington University in Saint Louis, Missouri, which had recently established a paleontology program, and asked if they would like to take a crack at excavating the site. SURE! So in the Summer of 2006, a team from Wash.U. arrived on the scene and conducted the first dig season at Stikes Quarry. The first of several large blocks was collected, hauled out of the site using an old car hood as a sled, and was afterwards transported to Saint Louis for study (26).

Karen Poole, a graduate student from Washington University (left), and Utah state paleontologist Dr. Jim Kirkland (right) examine the underside of the first bone jacket after it was turned upside-down. Utah Geological Survey. “Utahraptor Megablock Fossil Project: A Timeline of Excavation and Preparation”.
https://storymaps.arcgis.com/stories/8d63f2a68feb4a64a0ea5eebebdd9eaa.

One year, an extremely alarming event occurred at the dig site. As stated earlier, the fossils were found on the slope of a very steep ridge. The actual process of digging was rather precarious for the people involved, who needed to be conscious at all times of the potential for accidentally falling and hurting themselves, and also with the possibility of landslides. Unfortunately, that’s exactly what happened. Sometime between the conclusion of the 2006 dig season and the beginning of the 2007 season, a rockfall occurred at the site and smashed into the area which was excavated, including one section which was identified as containing fossils and which had been jacketed to protect it from the elements. The temporary plaster jacket which had been laid on the bones might have served well enough to guard against erosion, snow, and ice, but it could withstand a large rock weighing several hundred pounds dropping directly onto it. Regrettably, numerous fossils were damaged and several were destroyed. This incident was a shocking wake-up call for all of the Utah Geological Survey dig team members. The longer they took, the more likely incidents like this were going to happen in the future. They needed to come back to the site as frequently as possible and continue excavating before any more fossils were lost. Their first job was to salvage as much as possible from the material that had been damaged, and then they could start once more on fresh digging (27).

The horror…the horror… Gary Hunt, an intern working for the Utah Geological Survey, gazes upon the damage caused by several large rocks falling and smashing themselves into the excavation area. Regrettably, numerous fossils were damaged and several were destroyed. Utah Geological Survey. “Utahraptor Megablock Fossil Project: A Timeline of Excavation and Preparation”.
https://storymaps.arcgis.com/stories/8d63f2a68feb4a64a0ea5eebebdd9eaa.

Another problem that the paleontologists needed to contend with were other people visiting the site when they weren’t around. Perched high up on a steep slope, the dig site was plainly visible from miles away. Unfortunately, when the diggers came back for another excavation season, they could plainly see that somebody else had been digging there before them – fossil poachers. It’s impossible to know how much material was stolen (28).

In total, paleontologists spent nine dig seasons working on the site. Only the first of these was carried out by Washington University; the remainder were conducted by the Utah Geological Survey. Like the Gaston Quarry and the Dalton Wells Quarry, the rock layer at Stikes Quarry also dated to the upper part of the Yellow Cat Member of the Cedar Mountain Formation. The culmination of their efforts was a massive block crammed full of Utahraptor fossils weighing nine tons! Yet the Utahraptors were not the only animals found here. Several bones belonging to at least two individuals of an as-yet-unknown iguanodontian dinosaur (but it is possibly Hippodraco, based upon the description of the bones given by Karen Poole) were also found mixed into the matrix (29).

A preliminary analysis of the site suggested that these were the remains of numerous individuals who were trapped in quicksand. Usually, paleontologists excavating sites will try to make the bone jackets as small as possible in order for them to be carried manageably from the dig locality to the labs. However, in this case, that wasn’t possible. The bones were small, fragile, tightly packed together, and seemingly interwoven with each other. Breaking this massive block into several smaller blocks would assuredly damage many of the specimens preserved within it. So, this massive 9-ton block of rock needed to be excavated and carried out IN ONE PIECE (30).

The Stikes Quarry fossil block in the process of being jacketed and excavated. Utah Geological Survey. “Utahraptor Megablock Fossil Project: A Timeline of Excavation and Preparation”.
https://storymaps.arcgis.com/stories/8d63f2a68feb4a64a0ea5eebebdd9eaa.

Now that the block was fully jacketed, there came the dreadful dilemma of how to actually get it out. One proposal was that a helicopter could air-lift the block out of the site, but that was easier said than done. The Utah National Guard wanted to help, but they didn’t have any helicopters that were powerful enough to lift such a massive heavy object. There was nothing else to do but transport it the old-fashioned way – by physically lugging it out over-land (31).

A road needed to be made specifically for the purpose of pulling this block out. Normally, this would not be allowed on state-owned land, but Jim Kirkland was a state employee, so he authorized its construction. Don Brummel of Amex Construction was contracted to make the road, which was completed in 2012. In 2014, Phil Policelli, a dig volunteer and a member of Utah Friends of Paleontology, used his expertise in mechanical engineering to design a sled made of timbers and mounted on a pair of metal skids. Meanwhile, Dan Harrison and his son Bo who worked for High Desert Excavating offered the use of a bulldozer in order to fine-tune the road which had been graded earlier, and also offered to employ a track hoe excavator to drag the 9-ton block on its wooden sled down the road for a length of half a mile to a waiting flat-bed truck, which had been provided by Jim Cross of “Cross Marine Projects, Inc.”, who has been a longtime supporter of the UGS Paleontology Program (32).

Finally in November 2014, the big day came – time to pull out the fossil block. A video team from National Geographic had arrived on the site in order to document the event. It was a slow nail-biting nerve-wracking ordeal, but the job was done. The massive fossil block was put on Jim Cross’ truck and hauled to the Utah Geological Survey lab in Salt Lake City (33).

An excavator drags the 9-ton fossil block on a wooden sled down the steep slope – a very precarious business. Utah Geological Survey. “Utahraptor Megablock Fossil Project”.
https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/megablock/.

After the massive ordeal of digging out and transporting the 9-ton fossil block, it had arrived at its destination…or so everyone thought. It was intended that the block would be housed inside the UGS’s lab, but unfortunately, the block was so huge that it wouldn’t fit through the door. For a while, the UGS lab’s parking lot became the fossil block’s temporary home. Everyone began a frantic search for a place to store it long term so that it wouldn’t be left out in the elements. The initial plan was for it to be housed at the University of Utah, but the university’s floors weren’t strong enough to hold up such a massive weight. Finally, the Museum of Ancient Life in Lehi, Utah offered to house the block within their lab. The fossil block was transported there in 2015. The museum’s lab had a wide garage door, but not quite wide enough – the door was just a few inches too narrow. Ugh. So, Scott Madsen, who had been made the chief fossil preparator for this venture, had to do some fossil excavation right then and there. The block was temporary moved inside one of the museum’s maintenance buildings, a section of the plaster jacket on the side of the block was taken off, and he was able to carefully extract some Utahraptor foot bones that were lying close to the surface. Once the block was trimmed down a bit, they tried once more to move the massive block into the museum’s lab. This time, the garage door was literally just wide enough for the fossil block to be squeezed through (34).

The 9-ton Utahraptor fossil block sitting out in the parking lot of the Utah Geological Service lab in Salt Lake City, Utah. Photograph from “The Utahraptor Project” Facebook page, image used with permission.

Scott Madsen does some fossil prep work on the Stikes Quarry fossil block at the Museum of Ancient Life in 2016. Utah Geological Survey. “Utahraptor Megablock Fossil Project”.
https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/megablock/.

For the next five years, the Museum of Ancient Life’s lab was this block’s home, and a great deal of work was done on it during that time. It’s estimated that dozens of Utahraptor skeletons lie crammed together within this block, ranging from fully-grown adults, to juveniles, to babies. But then in early 2020, there was bad news. The block was taking up far too much room in the museum’s lab, the work was going very slowly, and the museum needed the lab space to work on other projects. So, the block was going to be evicted. It would be transported back to Salt Lake City, this time housed within a storage building at the Utah Core Research Center (UCRC) which had been reconfigured into a fossil preparation lab specifically to house this one massive block, which had been named “Raptor Bay”. In the long-run, this was best, because it allowed paleontologists and students operating from the UGS and from the Utah Museum of Natural History to have better access to it. On February 26, 2020, the fossil block was relocated back to Salt Lake City (35).

Then, the virus came.

In March 2020, the world went into quarantine as the coronavirus pandemic swept across the globe. The Museum of Ancient Life in Lehi, Utah had to temporarily close down. However, the Utahraptor fossil block was no longer in Lehi, but in its own special lab, and as such, preparation work could continue on it throughout the year (36).

The work which has been done so far has already contributed greatly to furthering our knowledge about Utahraptor’s anatomy. Just as Jim Kirkland and his colleagues had supposed back in 1993, it appears that Utahraptor was much bulkier and stockier than others in the dromaeosaurid family. For instance, it had thicker robust legs and a large boxy rectangular head compared to other raptors. Overall, it was similar in some respects to the larger carnosaurs that roamed the Jurassic rather than the lithe wolf-like predators that we associate raptors as being. Utahraptor was no wolf – it was more like a full-size Kodiak grizzly bear. One of the specimens which had been uncovered from Stikes Quarry was the front of an adult’s lower jaw, fitted with six teeth (collection ID code: UMNH VP 20501). The front teeth of the lower jaw are angled forwards (the scientific term for this is “procumbent”) instead of pointing straight up-and-down. But is this a diagnostic feature of Utahraptor’s appearance, or is this just a physical defect in one individual? Until more specimens are uncovered and examined, we cannot know for sure.

An updated depiction of the skeleton of Utahraptor, based upon the new fossils which were uncovered from Dalton Wells and from the 9-ton fossil block from Stikes Quarry. © Scott Hartman (2017), image used with permission. It is possible that such depictions will be updated yet again in the future as more and more fossils are uncovered and studied.

By the beginning of 2021, over 3,500 hours of fossil prep work had been carried out on the 9-ton Stikes Quarry fossil block (37). Excavation and preparation of this massive block is a slow methodical pains-taking process, and it’s still ongoing. This is largely due to the block’s sheer massive size, the fact that there are so many small specimens crammed together that need to be very carefully separated, and, at the time that I’m writing this article in late June 2022, only ONE fossil preparator is working on this huge stone block, and funding to carry out the work is very limited. The museum has therefore been reaching out to the public to ask for donations to carry out the work. Please check out “The Utahraptor Project” for updates, and to donate to this important scientific project. Please follow them on Facebook at https://www.facebook.com/The-Utahraptor-Project-1740182959575280. If you want to donate, please check out the Utah Geological Survey’s “Utahraptor Megablock Fossil Project” at https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/megablock/. You can get more specific info about donations by going here: https://geology.utah.gov/docs/pdf/STEM-utahraptor-megablock-letter.pdf.

Utahraptor’s World: North America during the Early Cretaceous Period, 135 Million Years Ago

From the early 1990s up to the late 2010s, it was believed that the rock layers where the Utahraptor bones had been found dated to around 125 MYA, the same time that creatures such as Iguanodon and Baryonyx existed (38). However, due to advancements in dating techniques, it is now believed that the upper Yellow Cat Member is somewhat older than this and actually dates from 135 to 132 MYA (39). So, what did Utahraptor’s world look like during this time?

During the 1970s, thanks to fossil finds in North America which are traditionally associated with the early Cretaceous of Europe, it was proposed that western Europe was connected to the northern part of North America during the late Jurassic and early Cretaceous Periods via a trans-Atlantic land bridge. Numerous scientific studies carried out during the 1990s, 2000s, and 2010s re-affirmed this. In particular, Leonidas Brikiatis’ 2016 report was the most thorough. In it, he states that it wasn’t until 129 MYA that the ever-growing Atlantic Ocean expanded to such an extent that North America was at last permanently severed from Europe. For a period afterwards measuring approximately twenty-five or so million years, North America was completely isolated from the rest of the Mesozoic world. It wouldn’t be until the late Albian Stage about 105-100 MYA that a second land bridge appeared, this time spanning the northern Pacific, connecting Alaska with Russia (40).

Map of North America, circa 135 MYA. Upper Yellow Cat Member of the Cedar Mountain Formation. Middle Valanginian Stage, early Cretaceous Period. Slattery, Joshua S.; Cobban, William A.; McKinney, Kevin C.; Harries, Peter J.; Sandness, Ashley L. (2013). “Early Cretaceous to Paleocene Paleogeography of the Western Interior Seaway: The Interaction of Eustasy and Tectonism”. Wyoming Geological Association, 68th Annual Field Conference (June 2013). Page 33.

Because the Atlantic Ocean was still in the process of growing during the late Jurassic and early Cretaceous, and had not yet completely split North America from Europe, it was possible for animal species to travel between the two continents via this trans-Atlantic land bridge – the scientific term for this is “faunal interchange”. Evidence for this consists of animals which are traditionally associated with Europe such as megalosaur theropods, turiasaurian sauropods, and iguanodont ornithopods also being found within North America. If faunal interchange could occur one way, then it’s certainly plausible that it could go the other way as well. The possibility that Utahraptor might have migrated to Europe was demonstrated in the 1999 BBC television series Walking With Dinosaurs. However, there is currently no hard evidence that Utahraptor or any large dromaeosaurid lived in Europe during this time.

In general, the environment of central Utah during the time that Utahraptor was alive was not too dissimilar from the Morrison Formation which had existed ten million years earlier. The Morrison Formation of the late Jurassic Period, where creatures such as Allosaurus, Stegosaurus, and Diplodocus lived, has been intensely studied ever since the late 1800s. Thanks to these studies, we know that the Morrison Formation was a flat semi-arid savannah-like landscape, consisting of broad plains separated from each other by rivers lined with forests. The climate was hot and dry, consisting of a short wet season and a prolonged dry season.

Eberth et al (2006) described the prehistoric landscape of the upper Yellow Cat Member as an “internally-drained” landscape (41). This means that streams, creeks, and rivers did not flow outwards towards the coast and eventually merging with the sea, but instead flowed into a depression in the surface of the landscape forming a large lake or possibly a series of lakes. This is borne out by examinations of the taphonomy of the Dalton Wells and Stikes Quarry excavation sites. At Dalton Wells, the four stacked debris flows which were likely caused by seasonal floods are capped by thin layers of sandstone, and over this is a layer of desiccated marl with sauropod and ornithopod footprints indicating the shore of a lake. The lake was apparently shallow but stable, fed by flood waters (42). The presence of marl in the Dalton Wells locality is especially noteworthy. “Marl” is a mixture of clay and calcium carbonate which is often formed in and around freshwater lakes whose water has an elevated pH level, often with a pH of 8.0 or even higher, making the water distinctly alkaline. The water of the lake will often have high levels of dissolved calcium carbonate within it.

Regarding the upper Yellow Cat Member, the presence of such a topographic feature – a large depression in the surface forming an internally-drained landscape – would explain how a semi-arid environment with a prolonged dry season was able to support a large and diverse population of dinosaurs. In fact, we know of at least one very large lake which existed in this landscape during that time which has been christened “Lake Madsen” (named after Scott Madsen, who discovered the site in 2005), and which covered approximately 100 square miles of area (43). That’s almost the same size as modern-day Bear Lake (which measures 109 square miles) which is located on the border between Idaho and Utah. Also, Bear Lake is an alkaline lake which possesses high amounts of dissolved calcium carbonate within the water – Lake Madsen would have visibly looked similar to this. Despite the elevated pH level of the water, many species of animals and plants can survive within. Among them is cyanobacteria, commonly referred to as “blue-green algae”, even though it’s not actually a type of alga at all. Wouldn’t you know, preserved microscopic remains of cyanobacteria have been found within the rocks recovered from Stikes Quarry (44). Fossils recovered from the Lake Madsen shale also include ostracods, conchostracans, and even the remains of freshwater hybodont sharks like Polyacrodus (45).

Bear Lake, which straddles the Idaho-Utah border. Photograph by Ron Reiring (August 14, 2007). Creative Commons Attribution 2.0 Generic license.
https://www.flickr.com/photos/84263554@N00/1143965838/.

Concretion deposits found within the rocks at Dalton Wells show evidence of groundwater seeping upwards through the soil. It therefore appears that in addition to evidence of large lakes within this region during the early Cretaceous Period, there were also numerous springs and watering holes scattered throughout the area as well (46).

In general, the landscape of eastern Utah during the upper Yellow Cat Member 135 MYA bears a strong similarity to the modern-day Etosha Pan of northern Namibia, in which a large depression in the land’s surface fills with water every monsoon season, forming a large shallow lake, located within a broad flat arid savannah landscape, accompanied by groundwater seeps forming watering holes in scattered locations around the lake’s perimeter and on the broad plains beyond (47). Another example would be Lake Makgadikgadi (pronounced as “Ma-KAH-dee-KAH-dee”) in Botswana, a once-massive lake which dried up thousands of years ago, the only remnant of which today is the Okavango Delta. Like the Etosha Pan, this lake was formed by a large depression in the earth’s surface. However, unlike the Etosha Pan, this was not a seasonal lake which was filled with water only during the monsoon season, but was a perennial waterbody fed by multiple rivers flowing into it, keeping this basin filled with fresh water year-round. However, thousands of years ago, an uplift in the earth’s crust diverted the courses of these rivers away from the Makgadikgadi Basin, and eventually this once massive lake dried up, leaving behind expansive salt flats (48).

Similar geologic processes occurred in North America during the early Cretaceous Period. During the earliest part of the Cretaceous Period, a period of mountain-building known as the “Sevier Orogeny” was taking place to the west. As the Pacific plate pushed against North America’s Pacific coastline and subducted itself underneath the North American plate, the crust within the interior of North America buckled upwards. This uplift of the earth’s crust had the effect of altering the overall topography of western North America. This transformed the landscape east of this slowly-rising mountain range (called the “Sevier Fold-Thrust Belt”) from being an “internally-drained basin” to being a “foreland basin” – the land gently sloped downwards towards sea level, eventually making its way towards the coastline of the seaway which was even then beginning to slowly-but-steadily encroach into the North American interior (49).

General flow directions of prehistoric rivers in North America during the early Cretaceous Period, as indicated within the rocks of the Cedar Mountain, Burro Canyon, and Lakota Formations. Map of North America during the Valanginian Stage from Slattery, Joshua S.; Cobban, William A.; McKinney, Kevin C.; Harries, Peter J.; Sandness, Ashley L. (2013). “Early Cretaceous to Paleocene Paleogeography of the Western Interior Seaway: The Interaction of Eustasy and Tectonism”. Wyoming Geological Association, 68th Annual Field Conference (2013) page 33. Fluvial flow indicators are based on information in Kirkland, James I.; Suarez, Marina; Suarez, Celina; Hunt-Foster, ReBecca (2016). “The Lower Cretaceous in East-Central Utah—The Cedar Mountain Formation and its Bounding Strata”. Geology of the Intermountain West, volume 3 (October 2016). Page 104; Miller, Roger D. (2016). “The Lower Cretaceous Cedar Mountain Formation of Eastern Utah: A Comparison with the Coeval Burro Canyon Formation, Including New Measured Sections on the Uncompahgre Uplift”. Master’s degree thesis, Utah State University. Pages 5-8, 13; Waagé, Karl M. (1959). “Stratigraphy of the Inyan Kara Group in the Black Hills”. U.S. Geological Survey Bulletin, 1081-B. Washington, D.C.: United States Government Printing Office, 1959. Page 47; Dahlstrom, David J.; Fox, James E. (1995). “Fluvial architecture of the lower Cretaceous Lakota Formation, Southwestern Flank of the Black Hills Uplift, South Dakota”. U.S. Geological Survey Bulletin, 1917-S. Washington, D.C.: United States Government Printing Office, 1995. Page 2.

During the time of the lower Yellow Cat Member around 139 to 136 million years ago, Utah seems to have become noticeably wetter and greener compared to what it had been earlier during the late Jurassic. However, this wet humid interval didn’t last long, and during the upper Yellow Cat Member from 135-132 MYA, the landscape reverted back to its previous Morrison-type environment. While there is evidence of rivers flowing across the landscape, and while fossils of fish, turtles, crocodiles and even small freshwater sharks have been found here, the general evidence suggests that the terrain of the upper Yellow Cat was significantly drier compared to what it was like a few million years earlier. The landscape of eastern Utah during the upper Yellow Cat Member of the early Cretaceous has been interpreted as a semi-arid floodplain, with forests growing in close proximity to riverbanks separated from each other by vast open prairies. The climate has been interpreted as being warm-to-hot year-round, and having a prolonged dry season and a short-but-intense wet season, due to the paleosols showing alternating periods of saturation and dehydration. There is evidence for wildfires occurring within this landscape, caused by lightning strikes within areas of dried tinder. The sudden massive rainfall during the wet season could cause flash floods (as is evident from the Dalton Wells Quarry), and large amounts of standing water would remain in place for prolonged periods of time, possibly soaking into the ground and forming pockets of quicksand (as seen in the Stikes Quarry) (50).

The Cedar Mountain Formation is most well-known for its dinosaur fossils. However, the landscape was also populated by lungfish, semionotid fish, freshwater hybodont sharks, tuatara-like sphenodonts, turtles, crocodylomorphs, mammals, and pterosaurs. Utahraptor shared its environment with at least three different species of iguanodont ornithopods including one with a prominent ridge running down the middle of its back, a small hypsilophodont, the armored nodosaurid ankylosaurian Gastonia, the brachiosaurid sauropod Cedarosaurus, the turiasaurian sauropod Moabosaurus, the therizinosaurid (or possibly an oviraptorosaur, but this is unlikely) theropod Martharaptor, and the primitive ornithomimosaurian theropod Nedcolbertia. The presence of so many prey items within this environment must have presented ample supplies of game for Utahraptor to hunt (51).

Yet as impressive as Utahraptor is, there is evidence that it may not have been the top predator within its environment. Teeth and a handful of bones which have been identified as belonging to a large theropod dinosaur have been recovered from the Cedar Mountain Formation. Although the remains of this animal have so far proven sparse, they are nevertheless clear enough to determine that they belonged to a large meat-eating dinosaur measuring perhaps 30 to 35 feet long. In the 1993 article which named Utahraptor, Jim Kirkland and his colleagues made the following statement: “The presence of a much larger ‘carnosaur’ with Utahraptor at the Dalton Well site raises the question as to how the role of [the] large predator was divided between these two large theropods. A great deal of research will be needed before this question can be approached” (52).

Fossil plants within the Yellow Cat Member are much rarer compared to animal fossils, and consist largely of preserved pollen and spores. Even so, the amount and variety of plant pollen remains from the Cedar Mountain Formation is much greater than any other contemporaneous early Cretaceous locality. One form of pollen, which has been given the classification Classopollis classoides, has been identified as coming from a conifer tree from the extinct conifer family Cheirolepidiaceae; this particular pollen constitutes over half of all of the preserved pollen specimens found here. Additionally, pollen from Exesipollenites tumulus forms almost one-third of the preserved pollen specimens. Pollen has also been identified which belongs to araucaria trees, although it is a relatively small percentage. Additionally, pollen has been found from the extinct seed fern order Caytoniales (the exact genus can’t be determined), but it’s very rare. Spores from ferns, mosses, and club mosses are found in much smaller numbers compared to seeds, likely due to preservation bias. In total, within the rocks of the Yellow Cat Member, paleo-botanists have identified fossilized seeds and spores from 9 species of conifer trees (1 cheirolepidiacean, 2 araucarians, 1 podocarp, and 5 pines), 1 species of seed fern, 18 species of ferns, 2 species of moss, 2 species of hornworts, 1 species of liverwort, 1 species of club moss, and 3 species of algae. No evidence of flowers has been found within any rocks dated to the Yellow Cat Member, but that’s very understandable, since the oldest-known flower fossils that we have date to around 130 MYA, during the early stages of the Poison Strip Member which came afterwards (53).

Conclusion

For a long time, the Cedar Mountain Formation was neglected in terms of academic scholarship, which meant that our understanding of what life was like in North America during the early Cretaceous Period was very limited. However, from the early 1990s onwards, the Cedar Mountain Formation came under increased attention from geologists and paleontologists. This was largely due to the discovery of Utahraptor, which grabbed not only the attention of professional academics but also the attention of the media and the general public. There was a growing interest as to what else might be hidden within those rocks, and so paleontologists and geologists began to examine the rock layers of the Cedar Mountain Formation much more earnestly. Thanks to Utahraptor’s discovery, numerous dinosaurs and other animals have been discovered and classified from this once-neglected geologic formation.

Riding high on the dinosaur fever that swept the world throughout the 1990s thanks to the fame of the 1993 movie Jurassic Park, Utahraptor was marketed as the ultimate raptor, twice as bad-ass as the raptors from Jurassic Park, and it took the world by storm. It was featured in countless examples of paleo-art and remains a popular topic with artists today. It also spawned the creation of toys, models, children’s books, and even a novel. It appeared in dinosaur documentaries, and it even appeared in Walking With Dinosaurs, albeit in England instead of in Utah.

Utahraptor toy, 1:40 scale (6 inches long), released by Battat Toys in 1994 as part of the “Boston Museum of Science Collection” (in direct competition with Safari Ltd.’s “Carnegie Collection”). The toy’s appearance is clearly based upon the Deinonychus statues made by Stephen Czerkas.

In addition to gaining attention from the media, artists, and dino-loving children all over the world, Utahraptor has also garnered a certain degree of political notoriety. On March 16, 2018, Governor Gary Herbert of Utah signed a bill into law officially designating Utahraptor as Utah’s state dinosaur (54). Three years later on April 13, 2021, Governor Spencer Cox of Utah signed HB 257 into law, and “Utahraptor State Park” was born. The exact dimensions of the park have not yet been finalized, but it is anticipated that it will measure 7,000 to 8,000 acres in area, including the Dalton Wells Quarry (55).

And yet, there is much work that still needs to be done. Out of the 800 or so specimens that were uncovered at Dalton Wells during the mid-to-late 1970s, only a small number have been studied. Yes, some of those which had been studied were shown to belong to Utahraptor, but there might very well be more within that vast collection which haven’t been looked at yet. The nine partial skeletons which were uncovered at Dalton Wells during the mid 90s are still undergoing preparation and analysis nearly thirty years after they were found, and it is unknown at this moment when the research’s findings are going to be published. Furthermore, considering that the Dalton Wells Quarry occupies such a vast swath of territory, and only a small section of it has been excavated so far (only 4.5% of the site’s total area), it is very possible that even more Utahraptor fossils are still lying there buried within the rock waiting to be discovered. The finds which were made at Stikes Quarry from 2005-2014 have gained much more public attention due to social media, but the work is very slow-going, and it will likely be years or even decades before any in-depth information is published.

Even so, the major task concerning all of this has already been accomplished – the fossils have been found, they’ve been excavated, and they are safely housed in various research institutions. Now, it’s up to others to continue the work, and who knows what new revelations will be unearthed? It seems clear to me that the 21st Century is going to be absolutely EPIC for Utahraptor research. With numerous skeletons discovered belonging to individuals ranging from babies to fully-grown adults, we are almost certainly going to have a much fuller view of Utahraptor’s anatomy and growth patterns compared to any other raptor dinosaur. And what about behavior? Are we going to uncover concrete proof that Utahraptor lived and hunted in family packs? Did the youngsters have different diets compared to the adults? Only time and a lot of research will answer these questions and assuredly the hundreds of others that are likely to follow in the years to come.

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Kirkland, James I.; Suarez, Marina; Suarez, Celina; Hunt-Foster, ReBecca (2016). “The Lower Cretaceous in East-Central Utah—The Cedar Mountain Formation and its Bounding Strata”. Geology of the Intermountain West, volume 3 (October 2016). Pages 101-228.
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McDonald, Andrew T.; Kirkland, James I.; DeBlieux, Donald D.; Madsen, Scott K.; Cavin, Jennifer; Milner, Andrew R. C.; Panzarin, Lukas (2010). “New basal iguanodonts from the Cedar Mountain Formation of Utah and the evolution of thumb-spiked dinosaurs”. PloS One, volume 5, issue 11: e14075.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014075.

Phillips, Stephen P.; Howell, John A.; Hartley, Adrian J.; Chmielewska, Magda; Hudson, Samuel M. (2021). “Evolution of foreland basin fluvial systems in the mid-Cretaceous of Utah, USA (upper Cedar Mountain and Naturita formations)”. Sedimentology, volume 68 (2021). Pages 2,097-2,124.
https://onlinelibrary.wiley.com/doi/pdf/10.1111/sed.12845.

Poole, Karen Elaine (2008). “A New Specimen of Iguanodontian Dinosaur from the Cedar Mountain Formation, Grand County, Utah”. Master’s thesis, Washington University, Saint Louis, Missouri (August 2008). Pages 1-56.

Royo-Torres, Rafael; Upchurch, Paul; Kirkland, James I.; DeBlieux, Donald D.; Foster, John R.; Cobos, Alberto; Alcalá, Luis (2017). “Descendants of the Jurassic turiasaurs from Iberia found refuge in the Early Cretaceous of western USA”. Scientific Reports, volume 7, issue 1 (October 30, 2017). Pages 1-12.
https://www.researchgate.net/publication/320717437_Descendants_of_the_Jurassic_turiasaurs_from_Iberia_found_refuge_in_the_Early_Cretaceous_of_western_USA.

Santa, Claire; Muller, David; Ilsemann, Lara; Simpson, Edward L.; Wizevich, Michael; Kirkland, James I. (2019). “Implications of cyanobacterial communities preserved in the early Cretaceous Stikes Dinosaur Quarry: Upper Yellow Cat member, Cedar Mountain Formation, Eastern Utah, USA”.  GSA Annual Meeting in Phoenix, Arizona, USA – September 22-25, 2019 (September 23, 2019).
https://gsa.confex.com/gsa/2019AM/webprogram/Paper333318.html.

Scheetz, Rodney; Britt, Brooks; Higgerson, Jeff (2010). “A large, tall-spined iguanodontid dinosaur from the Early Cretaceous (Early Albian) basal Cedar Mountain Formation of Utah”. Journal of Vertebrate Paleontology, volume 30, supplement 2 (October 2010). Page 158A.

Sprinkel, Douglas A.; Madsen, Scott K.; Kirkand, James I.; Waanders, Gerald L.; Hunt, Gary J. (2012). “Cedar Mountain and Dakota Formations around Dinosaur National Monument: Evidence of the First Incursion of the Cretaceous Western Interior Sea into Utah”. Utah Geological Survey Special Study 143 (2012). Pages 1-20.
https://ugspub.nr.utah.gov/publications/special_studies/SS-143/SS-143.pdf.

Stewart, J. D.; Hakel; Marjorie (2006). “Ichthyofauna of the Mowry Shale (Early Cenomanian) of Wyoming”. In New Mexico Museum of Natural History and Science Bulletin 35. Late Cretaceous Vertebrates from the Western Interior. Spencer G. Lucas and Robert M. Sullivan, eds. Albuquerque: New Mexico Museum of Natural History and Science, 2006. Pages 161-163.

Suarez, Celina A.; González, Luis A.; Ludvigson, Gregory A.; Kirkland, James I.; Cifelli, Richard L.; Kohn, Matthew J. (2014). “Multi-Taxa Isotopic Investigation of Paleohydrology in the Lower Cretaceous Cedar Mountain Formation, eastern Utah, U.S.A.: Deciphering Effects of the Nevadaplano Plateau on Regional Climate”. Journal of Sedimentary Research, volume 84 (November 2014). Pages 975-987.
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.724.2968&rep=rep1&type=pdf.

Websites

Paleofile. “Utahraptor”. http://www.paleofile.com/Dinosaurs/Theropods/Utahraptor.asp. Accessed on June 23, 2022.

Utah Department of Natural Resources. “Utahraptor State Park Fact Sheet and Background Information”. https://geology.utah.gov/docs/pdf/Utahraptor-fact-sheet.pdf.

Utah Friends of Paleontology. “Utahraptor Ridge: A Utah Landmark Named for a Landmark Discovery in Paleontology”. https://utahpaleo.org/2021/03/19/utahraptor-ridge/. Accessed on June 6, 2022.

Utah Geological Survey. “UGS Paleontologists Collect Dinosaur Megablock”, by Don DeBlieux. https://geology.utah.gov/map-pub/survey-notes/collect-dinosaur-megablock/. Accessed on June 6, 2022.

Utah Geological Survey. “Utahraptor Megablock Fossil Project”. https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/megablock/.Accessed on June 23, 2022.

Utah Geological Survey. “Utahraptor Megablock Fossil Project: A Timeline of Excavation and Preparation”. https://storymaps.arcgis.com/stories/8d63f2a68feb4a64a0ea5eebebdd9eaa. Accessed on June 23, 2022.

Videos

African Wildlife. National Geographic video, 1986.
https://www.youtube.com/watch?v=iZ1HCExLplU.

Nature, season 6, episode 13 – “Okavango: Jewel of the Kalahari, Part 1”. PBS (February 21, 1988).
https://www.youtube.com/watch?v=muaLL8ESFZk.

The Dinosaurs, episode 3 – “The Nature of the Beast”. PBS, 1992.
https://www.youtube.com/watch?v=0UDeojaTr9g.

Utah’s Dino Graveyard. The Discovery Channel, 2005.
https://www.youtube.com/watch?v=uJ918JXmzts.

YouTube. Natural History Museum of Utah. “Jim Kirkland: Utahraptors” (January 17, 2017). https://www.youtube.com/watch?v=1Rk5gaY23j4. Accessed on June 25, 2022.

YouTube. Utah Friends of Paleontology. “The Utahraptor Project: A Progress Report by Scott Madsen” (May 2, 2017). https://www.youtube.com/watch?v=DZXKTH3gy7M. Accessed on June 23, 2022.

YouTube. Utah Friends of Paleontology. “Preparation of the Utahraptor Megablock” (January 7, 2020). https://www.youtube.com/watch?v=S0rXWLHwK0E. Accessed on June 23, 2022.

YouTube. TheNMSR. “March 10th, 2021 NMSR Meeting – ‘Feathering Utahraptor: History of Dromaeosaur Discoveries’, hosted by Dr. Jim Kirkland” (March 15, 2021). https://www.youtube.com/watch?v=mY5lWGC-ogA. Accessed on March 14, 2022.

YouTube. Tate Geological Museum. “Tate Geological Museum’s Spring Lecture Series 2021: Cretaceous Dinosaurs- part 3 – The Cedar Mountain Formation of Utah: North America’s Most Complete Early Cretaceous Record, hosted by James I. Kirkland” (May 11, 2021). https://www.youtube.com/watch?v=Thhb6Jy-Acw. Accessed on March 14, 2022.



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