Dinosaur National Monument (Part 2)

Camarasaurus lentus is a sauropod species that lived 151.88-149.1 million years ago during the Late Jurassic. It is the most common dinosaur found at Carnegie Quarry and the most abundant sauropod in North America. C. lentus had shorter forelimbs than hindlimbs and grew up to 49 feet long but only weighed about 16.5 tons thanks to its hollow bones. It was shorter in length but taller in height than Diplodocus and Apatosaurus. C. lentus had a blunt snout and a squarish arched skull with chisel-shaped teeth for eating coarse plants that were replaced every 62 days on average. The genus was first described in 1877 by Edward Drinker Cope, who named it Camarasaurus, Greek for "chambered lizard," due to the holes in its vertebrae, called pleurocoels, which probably supported an air-sac system. In 1889, Othniel Charles March first described the species Morosaurus lentus, which was later reassigned as Camarasaurus lentus. The specific epithet lentusis Latin for “tough.” The only two skulls that can be seen on the “Wall of Bones” belong to C. lentus.

This skeleton cast represents a juvenile Camarasaurus lentus discovered by Earl Douglass at Carnegie Quarry in 1909. It is the most complete sauropod skeleton ever found. The fossil was found articulated in a death pose, a distinctive posture with the head thrown back, mouth open, and tail extended. The most complete adult C. lentus fossils also came from the Carnegie Quarry. Two of the 14 known sauropod specimens to preserve complete necks belong to C. lentus.

Abydosaurus mcintoshi is a sauropod species that lived 105.41-103.51 million years ago during the Early Cretaceous. It grew over 30 feet long and had narrow teeth unlike other early brachiosaurids. A. mcintoshi is known from four skulls and various bones discovered in the late 1990s in the Mussentuchit Member of the Cedar Mountain Formation near the old visitor center of Dinosaur National Monument. The species holotype, a skull found articulated with the lower jaws and first four cervical vertebrae, is the first complete sauropod skull from the Cretaceous of the Americas. The species was first described in 2010 by Daniel J. Chure, Brooks B. Britt, John A Whitlock, and Jeffrey A. Wilson. Since the holotype is a head and neck excavated by the Green River, they named the genus, Abydosaurus, Greek for "Abydos lizard," in reference to Abydos, the Greek name for a city on the Nile River where the head and neck of Osiris were buried in Egyptian mythology. The specific epithet, mcintoshi, was assigned in honor of sauropod expert John S. McIntosh, known for determining the correct skull of Apatosaurusat the Carnegie Museum. 

Allosaurus jimmadseni is another Allosaurus species that lived about 157.93-152.47 million years ago during the Late Jurassic. It differs from A. fragilis in skeletal details but is much rarer. A. jimmadseni was first discovered by George F. Engelmann in the Salt Wash Member of the Morrison Formation within Dinosaur National Monument in 1990. The fossil is one of the most complete skeletons of a carnivorous dinosaur from the Late Jurassic. Although only the left half of the skull was found, it provided a great deal of valuable information to differentiate the species, which was first described by Daniel J. Chure​ and Mark A. Loewen in 2020. They assigned it the specific epithet, jimmadseni, in honor of James H. Madsen, Jr, who led excavations at Cleveland-Lloyd Dinosaur Quarry in the 1960s and worked extensively on Allosaurus fossils. 

Deinonychus is another carnivore whose fossils were recently discovered at Dinosaur National Monument. Deinonychus antirrhopus is a dromaeosaurid species that lived 115–108 million years ago during the Early Cretaceous. Dromaeosauridae is a family of small to medium sized feathered theropods. Although no direct evidence has confirmed D. antirrhopus had feathers, they were probably present. It grew up to about 11 feet long and weighed between 132-220 pounds. It had powerful jaws with about 70 curved, blade-like teeth and unusually large sickle-shaped claws on the second digits of the hindlimbs, likely used during predation. Its forelimbs ended in large three-clawed hands where the first digit was shortest and the second was longest. Two quarries have yielded D. antirrhopus teeth in association with Tenontosaurusfossils, suggesting that D. antirrhopus may have hunted in packs to take down prey much larger than itself. The species was first described in 1969 by John Ostrom, who named it Deinonychus antirrhopus, Greek for “terrible claw counterbalance,” referring to its sickle-shaped talons and the presumed function of its stiffened tail. The clear active and agile nature of D. antirrhopus directly contributed to the Dinosaur Renaissance that started in the late 1960s. This was a period of renewed academic and popular interest in dinosaurs during which perceptions changed as Robert Bakker and John Ostrom strongly argued in support of the idea that some dinosaurs may have been warm-blooded. In 1974, Ostrom highlighted the similarity of the forelimbs of Deinonychus, Archaeopteryx, and birds, leading him to revive the hypothesis that birds descended from dinosaurs, an idea that is almost universally accepted today. Cranial and postcranial parts of an undescribed Deinonychusspecimen were discovered in the Ruby Ranch Member of the Albian at Dinosaur National Monument. The Velociraptors of the book and film, Jurassic Park, were modeled almost entirely after Deinonychus and the names were swapped simply because Velociraptor sounded “more dramatic.”

Camptosaurus aphanoecetesis an herbivorous ornithischian dinosaur species that lived about 156.3–146.8 million years ago during the Late Jurassic. Adults are estimated to have grown about 16-26 feet long and weighed between 1,102-1,987 pounds. C. aphanoecetes had short forelimbs but was most likely quadrupedal and it may have lived in small groups. It had a triangular skull ending in a beak and a jaw tightly packed with teeth used for consuming tough vegetation. C. aphanoecetes also had thumb spikes which were probably too small to have been used for defense. Camptosaurus is the ancestor of iguanodonts and hadrosaurids. The genus was first described in 1885 by Othniel Charles Marsh, who named it Camptosaurus, Greek for “flexible lizard,” referring to the presumed flexibility of the sacral vertebrae. Despite being found without a skull, the most complete Camptosaurus came from Dinosaur National Monument. It was on display in situ as Camptosaurus medius at Carnegie Museum for many years until the dinosaur exhibits were remodeled. When the fossil was removed from the rock to mount as a skeleton, it was discovered to be a new species. It was first described in 2008 by Kenneth Carpenter and Yvonne Wilson, who assigned it the specific epithet aphanoecetes, Greek for “to dwell hidden,” because it was “hidden” at the Carnegie Museum for over 75 years. A nine-inch fossilized C. aphanoecetes embryo was also discovered in the monument.

Dryosaurus elderae is an ornithopod species that lived 156.3-146.8 million years ago during the Late Jurassic. Ornithopoda is a clade of ornithischian dinosaurs that began as small, bipedal running herbivores that became larger and more numerous over evolutionary time. D. elderae grew as long as 9.8 feet and weighed up to 220 pounds. It had a long neck, long, slender legs, a long, stiff tail, short arms with five-fingered hands, a horny beak, and cheek teeth. Dryosaurus was first described as Laosaurus altusin 1878 by Othniel Charles Marsh. In 1894, he transferred it to the genus Dryosaurus, Greek for “tree lizard,” in reference to its forested habitat. In 2018, Dryosaurusfossils from Dinosaur National Monument were confirmed as a separate species by Kenneth Carpenter and Peter Malcolm Galton. They assigned the specific epithet elderaein honor of Ann Elder, who worked at the monument in the 1980s and 1990s. D. elderae is the smallest dinosaur found at Carnegie Quarry. An adult skull and juvenile skull excavated from the quarry are each the most complete of their kind ever found.

Ceratosaurusis a theropod genus that lived 153-148 million years ago during the Late Jurassic. It grew about 17-23 feet long and weight estimates for individuals vary greatly between 606-2,160 pounds. Ceratosaurus had very short four-clawed forelimbs, deep jaws with long, blade-like teeth, horns over the eyes, and a nasal horn that was likely used for display. It also had a series of small osteoderms, or skin bones, that ran down the neck, back, and tail unlike other theropods. Since Ceratosaurus coexisted with other large theropods such as Allosaurus and Torvosaurus, they may have occupied different ecological niches to reduce competition, with Ceratosaurushunting primarily near and within bodies of water. The genus was first described in 1884 by Othniel Charles Marsh, who named it Ceratosaurus, Greek for “horn lizard," because of the nasal bone crest. The only Ceratosaurusfossil known from Dinosaur National Monument is a premaxilla bone found at Carnegie Quarry.

Torvosaurus tanneri is a theropod species that lived 165–148 million years ago during the Late Jurassic. It was likely the largest theropod of its time in North America, growing about 30 feet long and weighing around 2.2 tons. T. tanneri had a lower, sinuous body that would have increased its hunting success in forest and underbrush environments and around active waterways. The species was first described in 1979 by Peter Galton and James Alvin Jensen, who derived the name Torvosaurus from the Latin word for "savage" and the Greek word for "lizard." The species epithet tanneri was named after Nathan Eldon Tanner, the first counselor in the First Presidency of the Church of Jesus Christ of Latter-day Saints. T. tanneri is one of the rarest theropods in the Morrison Formation and is known in Dinosaur National Monument from a single humerus bone recovered at Carnegie Quarry.

Barosaurus lentus is a sauropod species that lived around 152-150 million years ago during the Late Jurassic. Adults could weigh between 13–22 tons and grow 82–89 feet long, similar to Diplodocus but with a longer neck and shorter tail. B. lentus forelimbs were also longer and slenderer than those of Diplodocus. The species was first described in 1890 by Othniel Charles Marsh, who named it Barosaurus, Greek for “heavy lizard," and lentus, Latin for “tough.” B. lentus is the least common sauropod at Carnegie Quarry but one specimen removed from the quarry is among the most complete in the world. No Barosaurus skull has ever been found.

Freshwater mussels of the Vetulonaiagenus are the most abundant organisms preserved at Carnegie Quarry. The genus was first described in 1935 by C.C. Branson, who named it Vetulonaia, Latin for “old woman.”

Glyptops ornatus is an extinct freshwater turtle species that lived about 149.9-145 million years ago during the Late Jurassic. Its ornamented shell is the most common part of it preserved as fossils. G. ornatus retracted its head by folding its neck back vertically like modern box turtles, pond turtles, and tortoises. The species was first described in 1890 by Othniel Charles Marsh, who named it Glyptops ornatus, Greek for "decorated grooved face." G. ornatus is the most common turtle found in the Morrison Formation. An adult shell and juvenile shell found at Dinosaur National Monument are each the best preserved of their kind.

Dinochelys whitei is another extinct turtle species that lived during the Late Jurassic. The species was first described in 1979 by Eugene S. Gaffney, who assigned it to the genus Dinochelys, combining Dinosaur National Monument and chelys, Greek for turtle. The D. whiteiholotype is an adult specimen found at Dinosaur National Monument. No skulls have ever been found.

Opisthias rarus is an extinct sphenodont species that lived 155.6-145 million years ago during the Late Jurassic. Sphenodontia is a family of lizard-like reptiles whose fossils are common in Mesozoic Era rock and whose last living member is the tuatara of New Zealand. O. rarus grew up to the length of a foot or more. The species was first described in 1905 by Charles Whitney Gilmore, who reassigned it to the Opisthias genus in 1909. Opisthias is Greek for “rear” and rarus is Latin for “rare.”

Goniopholis is an extinct goniopholidid genus that lived 155–139.8 million years ago during the Late Jurassic and Early Cretaceous. Goniopholididae is an extinct family of medium-sized semiaquatic crocodyliforms and Crocodyliformes is a clade of pseudosuchian archosaurs that includes crocodilians and their closest relatives that possess many "crocodilian” traits. Goniopholis was very similar to modern crocodilians but had two rectangular, interlocking rows of osteoderms down its back as well as ventral osteoderms. The genus was first described in 1841 by Sir Richard Owen, who named it Goniopholis, Greek for “angled scale.”

Hoplosuchus kayiis an extinct crocodylomorph species that lived during the Late Jurassic. Crocodylomorpha is a clade of pseudosuchian archosaurs that includes crocodyliforms and their extinct relatives. H. kayi was a terrestrial running carnivore with conical, pointed teeth likely used for eating insects and small vertebrates. The only confirmed specimen was 7.9 inches long fully grown. It was discovered complete with the skull, limbs, vertebrae, and bony scutes at Dinosaur National Monument by paleontologist J. LeRoy "Pop" Kay. He sent his 10-year-old brother-in-law, Jesse York, to dig a hole for dynamite and the explosion unearthed the two halves of the fossil which were found among the scattered debris. The species was first described in 1926 by Charles Whitney Gilmore, who named its genus Hoplosuchus, or “armored crocodile.”

Iridotriton hechti is an extinct primitive salamander species that lived during the Late Jurassic. The only known fossil was discovered in the Rainbow Park Area of Dinosaur National Monument and it is the most complete salamander skeleton from the Jurassic of North America. The species was first described in 2005 by S.E. Evans, C. Lally, D.C. Chure, A. Elder, and J.A. Maisano, who named it Iridotriton, Latin for "rainbow newt," and hechtiafter Max Hecht, who studied Jurassic salamanders. 

Rhadinosteus parvusis an extinct frog species that lived 155.6-148.5 million years ago during the Late Jurassic and grew to about half an inch long. The only known specimens are over a dozen individuals found in a rock slab in the Rainbow Park Area of Dinosaur National Monument. One of the fossils is the only complete frog discovered in the Morrison Formation and one of few complete frogs from any time during the Jurassic. The species was first described in 1998 by Amy C. Henrici, who named it Rhadinosteus parvus, Latin for "small slender bone."

Glirodon grandisis an extinct multituberculate species that lived during the Late Jurassic. Multituberculata is an order of rodent-like mammals with no living members. Although it was not a true rodent, G. grandis had enlarged upper incisors and filled the niche that rodents fill today. The species was first described in 1999 by George F. Engelmann and G. Callison, who named it Glirodon, Greek for “rodent tooth,” and grandis, Latin for “large.” The Glirodon holotype is the front half of a skull discovered at Dinosaur National Monument and it is the most complete multituberculate skull from the Jurassic of North America.