Sarahsaurus

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Sarahsaurus
Temporal range: Early Jurassic,
199.3–182.7  Ma
Sarahsaurus.jpg
Illustration of the skull in multiple views
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade:† Sauropodomorpha
Clade:† Massopoda
Genus:† Sarahsaurus
Rowe, Sues & Reisz, 2011
Species:
†S. aurifontanalis
Binomial name
†Sarahsaurus aurifontanalis
Rowe, Sues & Reisz, 2011

Sarahsaurus is a genus of basal sauropodomorph dinosaur which lived during the Early Jurassic period in what is now northeastern Arizona, United States. [2]

Contents

Discovery and naming

Illustration of the bones in the holotype Sarahsaurus holotype.jpg
Illustration of the bones in the holotype

All specimens of Sarahsaurus were collected from the Lower Jurassic Kayenta Formation near Gold Spring, Arizona. [2] The genus is based on a nearly complete and articulated (with bones still connected to each other) skeleton with a fragmentary and disarticulated skull (holotype, specimen number TMM 43646-2). In addition, a partial skeleton (specimen number TMM 43646-3) as well as a nearly complete skull (specimen number MCZ 8893) was assigned to the genus. [2] The latter specimen was originally referred to as Massospondylus sp. [3] The complete skull is crushed and split horizontally, separating the skull roof from the palate; this split was caused by periodic swelling and shrinkage of the surrounding clay after burial. While the holotype individual was mature, the second skull indicates a less mature individual as indicated by open suture lines that separate skull bones of the braincase (the bones enclosing the brain). [2] [1]

Sarahsaurus was first described by Timothy B. Rowe, Hans-Dieter Sues and Robert R. Reisz in 2011; the type species is Sarahsaurus aurifontanalis. The generic name honours Sarah (Mrs. Ernest) Butler, an Austin philanthropist. She helped fund the "Dino Pit" exhibit at the Austin Nature and Science Center, which Rowe helped create; he was quoted as saying "I told [Sarah] if she really raised a million dollars to build the Dino Pit, I'd name a dinosaur after her.". [4] The specific name is derived from aurum (Latin), "gold", and fontanalis (Latin), "of the spring" in reference to Gold Spring, Arizona, where the holotype was found. Sarahsaurus is the fourth basal sauropodomorph dinosaur to have been officially identified in North America; the other three are Anchisaurus and Ammosaurus from the Early Jurassic of the Connecticut River Valley, and Seitaad of the later Navajo Sandstone of Early Jurassic Utah; a genus of basal sauropodmorph from Early Jurasssic deposits around Nova Scotia called Fendusaurus remains undescribed. [5] It is thought to have appeared through a dispersal event that originated in South America and was separate from those of the other two sauropodomorphs. [2] The animal is notable for possessing very large, powerful hands, possibly suggesting that it was an omnivore. [6]

Description

Sarahsaurus was a basal (or "primitive") member of the sauropodomorph lineage, which also included the more derived (or "advanced") sauropods – giant four-legged herbivores (plant-eaters) with long necks and tails. Basal sauropodomorphs such as Sarahsaurus already resemble sauropods in a number of aspects, including the elongated neck and robust build, but are reminiscent of the ancestral dinosaurs in others: Sarahsaurus was bipedal (two-legged), with forelimbs that were much shorter than the hind limbs and equipped with powerful grasping hands. [7] [1] Sarahsaurus was mid-sized for a basal sauropodomorph, with its vertebral column measuring more than 3.1 metres (10 ft) in length. [1] Paleontologist Gregory Paul, in a 2016 popular book, estimated its length at 4 metres (13 ft) and its body weight at 200 kilograms (440 lb). [8]

Skull

The external naris (skull opening for the nostril) was less than half the size of the orbit (eye socket). It was bordered by the nasal, premaxilla, and, to a small extent, the maxilla, the latter two forming the upper jaw. Between the premaxilla and maxilla there was a large opening, the subnarial foramen. The antorbital fossa, an additional skull opening seen in most dinosaurs that was situated between the external naris and orbit, was less than half the length of the orbit. Much of the upper margin of the orbit was formed by the frontal bone of the skull roof ; this bone, however, did not contribute to the front margin of the upper temporal fenestra at the rear end of the skull roof. Instead, this front margin was formed by the postorbital and parietal bones , with the front part of the parietal being forked to connect with the latter. Between the parietal and the supraoccipital, which follows behind the parietal at the back of the skull, was another opening, the postparietal fenestra, which was large in Sarahsaurus. A unique feature of the genus can be found on the underside of the braincase, where a shallow ridge spanned between the basipterygoid processes , bony downwards projections of the braincase that brace the latter against the palate . The lower jaw curved downwards towards its tip, and the jaw joint was located well below the level of the tooth row. There is no evidence for a beak. [2] [1]

Each side of the upper jaw was lined with 20 teeth – four in the premaxilla, the front bone of the upper jaw, and 16 in the maxilla which followed behind. The dentary bone of the lower jaw likewise had 20 teeth. The teeth were moderately heterodont, i.e., tooth shape varied within the jaw, and sat slightly obliquely in the jaw, slightly overlapping each other. Their cutting edges were serrated with up to 20 denticles per tooth. [2]

Postcranium

The spine comprised 10 cervical (neck) vertebrae; 14 dorsal (trunk) vertebrae; three sacral (hip) vertebrae; and ca. 50 caudal (tail) vertebrae. In contrast to the later sauropods, the sides of the dorsal vertebrae did not show deep cavities caused by air sacs invading the bone ( postcranial skeletal pneumaticity ). The scapula (shoulder blade) was hourglass-shaped. In the holotype specimen, the scapula and coracoid were unfused, probably connected only via cartilage; this might indicate that the individual was not yet fully mature. The holotype specimen includes the sternum (breastbone) and the clavicle (collarbone), which are rarely found with dinosaur skeletons. The clavicula is a rod-like bone that articulates with the lower end of the scapula in an immobile joint. It has been controversial if the left and right clavicles of sauropodomorphs were attached to each other at their ends, thus connecting the left and right shoulder girdles, or if they were pressed against their scapulae along their lengths. The orientation of the clavicle in Sarahsaurus confirms that the former was the case; the ends of both clavicles would probably have been connected to each other by a ligament, though they were not fused. In side view, the scapula was tilted between 45° and 65° relative to the horizontal. This would have allowed the left and right coracoids to almost touch each other at the body midline, while the left and right sterna, which were attached to each other at the midline, would have been located directly behind the coracoids. [2] [1]

The humerus (upper arm bone) was more than half the length of the femur (upper thigh bone), and had a large crest on its front side for muscle attachment, the deltopectoral crest , which extended for half the length of the bone and had an S-shaped edge. In the hand, the ungual (claw bone) of the first finger was the largest. [2]

In the hip, the ilium had two downwards-facing bony projections, the ischial and pubic peduncle, which connected to the two lower hip bones, the ischium and the pubis, respectively, as in other dinosaurs. In Sarahsaurus, the ischial peduncle was only half the length of the pubic peduncle. The acetabulum (hip joint) was formed by all three hip bones, as in other dinosaurs, though in Sarahsaurus the ischium contributed less than half as much as the pubis. The pubis was unique in having two separate openings, the obturator foramen and the pubic foramen; the latter was lacking in most other archosaurs. The femur was straight and elliptical in cross-section. The tibia (shin bone) reached 84% of the length of the femur. [2]

Classification

Holotype braincase in multiple views Sarahsaurus braincase.jpg
Holotype braincase in multiple views

In a cladistic analysis, presented by Apaldetti and colleagues in November 2011, Sarahsaurus was found to be most closely related to Ignavusaurus within Massopoda. Their group was found to be intermediate between plateosaurids and massospondylids, being more derived than the former and more primitive than the latter. [9] A 2018 cladistic analysis by Chapelle and Choiniere recovered Sarahsaurus and Ignavusaurus as massospondylids, mirroring the original assignment of Sarahsaurus to Massospondylus. [10]

Plateosauria
Plateosauridae

Unaysaurus

Plateosaurus

P. gracilis

P. engelhardti

P. ingens

Riojasauridae

Riojasaurus

Eucnemesaurus

Sarahsaurus

Ignavusaurus

Massospondylidae

Massospondylus

Leyesaurus

Adeopapposaurus

Coloradisaurus

Glacialisaurus

Lufengosaurus

Jingshanosaurus

Yunnanosaurus

Seitaad

Anchisauria

Paleoecology

Restoration Sarahsaurus restoration.PNG
Restoration

Age and habitat

A definitive radiometric dating of the Kayenta Formation has not yet been made, and the available stratigraphic correlation has been based on a combination of radiometric dates from vertebrate fossils, magnetostratigraphy and pollen evidence. [11] It has been surmised that the Kayenta Formation was deposited during the Sinemurian and Pliensbachian stages of the Early Jurassic period, approximately 199 to 182 million years ago. [12] The Kayenta Formation is part of the Glen Canyon Group that includes formations not only in northern Arizona but also parts of southeastern Utah, western Colorado, and northwestern New Mexico. The formation was primarily deposited by rivers. During the Early Jurassic, the land that is now the Kayenta Formation experienced rainy summers and dry winters. By the Middle Jurassic period it was being encroached upon from the north by a sandy dune field that would become the Navajo Sandstone. [13] The animals here were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes.

Paleofauna

Sarahsaurus shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus , Kayentavenator , [14] Coelophyisiskayentakatae, and the "Shake N Bake" theropod, and the armored dinosaurs Scelidosaurus and Scutellosaurus . The Kayenta Formation has yielded a small but growing assemblage of organisms. [15] Vertebrates present in the Kayenta Formation at the time of Saharasaurus included hybodont sharks, indeterminate bony fish, lungfish, salamanders, the frog Prosalirus , the caecilian Eocaecilia , the turtle Kayentachelys , a sphenodontian reptile, various lizards, and the pterosaur Rhamphinion . Also present were the synapsids Dinnebitodon , Kayentatherium , Oligokyphus , morganucodontids, the possible early true mammal Dinnetherium, and a haramiyid mammal. [16] Several early crocodylomorphs were present including Calsoyasuchus , Eopneumatosuchus , Kayentasuchus , and Protosuchus . [15] [16] [17] [18] Vertebrate trace fossils from this area included coprolites [19] and the tracks of therapsids, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present. [20] Non-vertebrates in this ecosystem included microbial or "algal" limestone, [19] freshwater bivalves, freshwater mussels and snails, [13] and ostracods. [21] The plant life known from this area included trees that became preserved as petrified wood. [17]

Related Research Articles

<i>Dilophosaurus</i> Genus of theropod dinosaur from Early Jurassic

Dilophosaurus is a genus of theropod dinosaurs that lived in what is now North America during the Early Jurassic, about 193 million years ago. Three skeletons were discovered in northern Arizona in 1940, and the two best preserved were collected in 1942. The most complete specimen became the holotype of a new species in the genus Megalosaurus, named M. wetherilli by Samuel P. Welles in 1954. Welles found a larger skeleton belonging to the same species in 1964. Realizing it bore crests on its skull, he assigned the species to the new genus Dilophosaurus in 1970, as Dilophosaurus wetherilli. The genus name means "two-crested lizard", and the species name honors John Wetherill, a Navajo councilor. Further specimens have since been found, including an infant. Footprints have also been attributed to the animal, including resting traces. Another species, Dilophosaurus sinensis from China, was named in 1993, but was later found to belong to the genus Sinosaurus.

Cryolophosaurus is a genus of large theropod dinosaur known from only a single species Cryolophosaurus ellioti, from the early Jurassic of Antarctica. It was one of the largest theropods of the Early Jurassic, with the subadult being estimated to have reached 6–7 metres (20–23 ft) long and weighed 350–465 kilograms (772–1,025 lb).

<i>Melanorosaurus</i> Sauropodomorph dinosaur genus from the Late Triassic period

Melanorosaurus is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. A herbivore from South Africa, it had a large body and sturdy limbs, suggesting it moved about on all fours. Its limb bones were massive and heavy like the limb bones of true sauropods.

<i>Massospondylus</i> Sauropodomorph dinosaur genus from Early Jurassic South Africa and Botswana

Massospondylus is a genus of sauropodomorph dinosaur from the Early Jurassic.. It was described by Sir Richard Owen in 1854 from remains discovered in South Africa, and is thus one of the first dinosaurs to have been named. Fossils have since been found at other locations in South Africa, Lesotho, and Zimbabwe. Material from Arizona's Kayenta Formation, India, and Argentina has been assigned to the genus at various times, but the Arizonan and Argentinian material are now assigned to other genera.

<i>Yunnanosaurus</i> Extinct genus of dinosaurs

Yunnanosaurus is an extinct genus of sauropodomorph dinosaur that lived approximately 199 to 183 million years ago in what is now the Yunnan Province, in China, for which it was named. Yunnanosaurus was a large sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could also walk bipedally, and ranged in size from 7 meters (23 feet) long and 2 m (6.5 ft) high to 4 m (13 ft) high in the largest species.

<span class="mw-page-title-main">Massospondylidae</span> Extinct family of dinosaurs

Massospondylidae is a family of early massopod dinosaurs that existed in Asia, Africa, North America, South America and Antarctica during the Late Triassic to the Early Jurassic periods. Several dinosaurs have been classified as massospondylids over the years. The largest cladistic analysis of early sauropodomorphs, which was presented by Apaldetti and colleagues in November 2011, found Adeopapposaurus, Coloradisaurus, Glacialisaurus, Massospondylus, Leyesaurus and Lufengosaurus to be massospondylids. This result supports many previous analyses that tested fewer taxa. However, this analysis found the two recently described North American massopods, Sarahsaurus and Seitaad, and the South African Ignavusaurus to nest outside Massospondylidae, as opposed to some provisional proposals. Earlier in 2011, Pradhania, a sauropodomorph from India, was tested for the first time in a large cladistic analysis and was found to be a relatively basal massospondylid. Mussaurus and Xixiposaurus may also be included within Massospondylidae. In 2019, a specimen previously assigned to Massospondylus from South Africa was re-examined and found to belong to a separate genus that was named Ngwevu.

<i>Glacialisaurus</i> Extinct genus of dinosaurs

Glacialisaurus is a genus of sauropodomorph dinosaur. It lived during the Pliensbachian stage of the Early Jurassic period around 186 to 182 million years ago in what is now the central region of the Transantarctic Mountains of Antarctica. It is known from two specimens; the holotype, a partial tarsus (ankle) and metatarsus, and a partial left femur. The fossils were collected by a team led by paleontologist William R. Hammer during a 1990–91 field expedition to the Hanson Formation of Antarctica. They were described in 2007, and made the basis of the new genus and species Glacialisaurus hammeri. The genus name translates as “icy” or "frozen lizard”, and the species name honors Hammer.

<i>Adeopapposaurus</i> Extinct genus of dinosaurs

Adeopapposaurus is a genus of prosauropod dinosaur from the Early Jurassic Cañón del Colorado Formation of San Juan, Argentina. It was similar to Massospondylus. Four partial skeletons with two partial skulls are known.

<i>Spinophorosaurus</i> Middle Jurassic genus of sauropod dinosaur

Spinophorosaurus is a genus of sauropod dinosaur that lived in what is now Niger during the Middle Jurassic period. The first two specimens were excavated in the 2000s by German and Spanish teams under difficult conditions. The skeletons were brought to Europe and digitally replicated, making Spinophorosaurus the first sauropod to have its skeleton 3D printed, and were to be returned to Niger in the future. Together, the two specimens represented most of the skeleton of the genus, and one of the most completely known basal sauropods of its time and place. The first skeleton was made the holotype specimen of the new genus and species Spinophorosaurus nigerensis in 2009; the generic name refers to what was initially thought to be spiked osteoderms, and the specific name refers to where it was found. A juvenile sauropod from the same area was later assigned to the genus.

Ignavusaurus is a genus of basal sauropodomorph dinosaur that lived during the Early Jurassic in what is now Lesotho. Its fossils were found in the Upper Elliot Formation which is probably Hettangian in age. It was described on the basis of a partial, well preserved articulated skeleton. The type species, I. rachelis, was described in 2010 by Spanish palaeontologist F. Knoll.

Kayentavenator is a genus of small carnivorous tetanuran dinosaur that lived during the Early Jurassic Period; fossils were recovered from the Kayenta Formation of northeastern Arizona and were described in 2010.

<i>Kayentachelys</i> Extinct genus of turtles

Kayentachelys is an extinct genus of turtle known only from the "silty facies" of the Lower Jurassic Kayenta Formation in northeastern Arizona on the lands of the Navajo Nation.

<i>Eodromaeus</i> Extinct genus of dinosaurs

Eodromaeus is an extinct genus of probable basal theropod dinosaurs from the Late Triassic of Argentina. Like many other of the earliest-known dinosaurs, it hails from the Carnian-age Ischigualasto Formation, within the Ischigualasto-Villa Unión Basin of northwestern Argentina. Upon its discovery, it was argued to be one of the oldest true theropods, supplanting its contemporary Eoraptor, which was reinterpreted as a basal sauropodomorph.

<i>Arcusaurus</i> Extinct genus of dinosaur from early Jurassic South Africa

Arcusaurus is an extinct genus of sauropodomorph dinosaur from the Early Jurassic of South Africa.

<i>Megapnosaurus</i> Extinct genus of dinosaur

Megapnosaurus is an extinct genus of coelophysid theropod dinosaur that lived approximately 188 million years ago during the early part of the Jurassic Period in what is now Africa. The species was a small to medium-sized, lightly built, ground-dwelling, bipedal carnivore, that could grow up to 2.2 m (7.2 ft) long and weigh up to 13 kg (29 lb). It was originally given the genus name Syntarsus, but that name was later determined to be preoccupied by a beetle. The species was subsequently given a new genus name, Megapnosaurus, by Ivie, Ślipiński & Węgrzynowicz in 2001. Some studies have classified it as a species within the genus Coelophysis, but this interpretation has been challenged by more subsequent studies and the genus is now considered valid.

This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.

<i>Coelophysis</i>? <i>kayentakatae</i> Extinct species of dinosaur

Coelophysis? kayentakatae is an extinct species of neotheropod dinosaur that lived approximately 200 - 196 million years ago during the early part of the Jurassic Period in what is now the southwestern United States. While originally assigned to the genus Syntarsus as Syntarsus kayentakatae, that genus name was found to be preoccupied by a Colydiine beetle, so it was moved to the genus Megapnosaurus as Megapnosaurus kayentakatae. Later it was moved again to Coelophysis, however the species still possesses no definite genus assignment.

<i>Buriolestes</i> Extinct genus of dinosaurs

Buriolestes is a genus of early sauropodomorph dinosaurs from the Late Triassic Santa Maria Formation of the Paraná Basin in southern Brazil. It contains a single species, B. schultzi, named in 2016. The type specimen was found alongside a specimen of the lagerpetid dinosauromorph Ixalerpeton.

<i>Xingxiulong</i> Extinct genus of reptiles

Xingxiulong is a genus of bipedal sauropodiform from the Early Jurassic of China. It contains a single species, X. chengi, described by Wang et al. in 2017 from three specimens, two adults and an immature individual, that collectively constitute a mostly complete skeleton. Adults of the genus measured 4–5 metres (13–16 ft) long and 1–1.5 metres tall. Phylogenetic analysis suggests that Xingxiulong is most closely related to its contemporary Jingshanosaurus, although an alternative position outside of both the Sauropodiformes and Massospondylidae is also plausible.

<i>Thalassodraco</i> Extinct genus of ophthalmosaurid ichthyosaur

Thalassodraco is an extinct genus of ophthalmosaurid ichthyosaur from the Late Jurassic (Tithonian) Kimmeridge Clay Formation of England. The type species, T. etchesi, was named in 2020, with the epithet in honour of the discoverer of the holotype, Steve Etches.

References

  1. 1 2 3 4 5 6 Adam D. Marsh, Timothy B. Rowe (2018):Anatomy and systematics of the sauropodomorph Sarahsaurus aurifontanalis from the Early Jurassic Kayenta Formation:https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0204007
  2. 1 2 3 4 5 6 7 8 9 10 Timothy B. Rowe, Hans-Dieter Sues and Robert R. Reisz (2011). "Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon". Proceedings of the Royal Society B: Biological Sciences. 278 (1708): 1044–1053. doi:10.1098/rspb.2010.1867. PMC   3049036 . PMID   20926438.
  3. ↑ Attridge, J.; A.W. Crompton; Farish A. Jenkins Jr (1985). "The southern Liassic prosauropod Massospondylus discovered in North America". Journal of Vertebrate Paleontology. 5 (2): 128–132. doi:10.1080/02724634.1985.10011850.
  4. ↑ "New Fossil Suggests Dinosaurs Not So Fierce After All".
  5. ↑ Fedak TJ. Description and evolutionary significance of the sauropodomorph dinosaurs from the Early Jurassic (Hettangian) McCoy Brook Formation. Ph.D. Dissertation, Dalhousie University. 2006.
  6. ↑ http://news.nationalgeographic.com/news/2010/10/101006-new-dinosaur-north-america-science/ [ dead link ]
  7. ↑ Yates, Adam M. (2012). "Basal Sauropodomorpha: The "Prosauropods"". In M. K. Brett-Surman; James O. Farlow; Thomas R. Holtz (eds.). The Complete Dinosaur (2 ed.). Indiana University Press. pp. 424–443. ISBN   978-0-253-35701-4.
  8. ↑ Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs (2nd ed.). Princeton, New Jersey: Princeton University Press. p. 189. ISBN   9780691167664.
  9. ↑ Cecilia Apaldetti, Ricardo N. Martinez, Oscar A. Alcober and Diego Pol (2011). Claessens, Leon (ed.). "A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina". PLOS ONE. 6 (11): e26964. Bibcode:2011PLoSO...626964A. doi: 10.1371/journal.pone.0026964 . PMC   3212523 . PMID   22096511.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ↑ Chapelle KEJ, Choiniere JN. (2018) A revised cranial description of Massospondylus carinatus Owen (Dinosauria: Sauropodomorpha) based on computed tomographic scans and a review of cranial characters for basal Sauropodomorpha. PeerJ 6:e4224 https://doi.org/10.7717/peerj.4224
  11. ↑ J. M. Clark and D. E. Fastovsky. 1986. Vertebrate biostratigraphy of the Glen Canyon Group in northern Arizona. The Beginning of the Age of the Dinosaurs: Faunal change across the Triassic-Jurassic boundary, N. C. Fraser and H.-D. Sues (eds.), Cambridge University Press 285–301
  12. ↑ Padian, K (1997) Glen Canyon Group In: Encyclopedia of Dinosaurs, edited by Currie, P. J., and Padian, K., Academic Press.
  13. 1 2 Harshbarger, J. W.; Repenning, C. A.; Irwin, J. H. (1957). "Stratigraphy of the uppermost Triassic and the Jurassic rocks of the Navajo country". Professional Paper. Vol. 291. Washington, D.C.: U.S. Geological Survey. doi:10.3133/pp291. S2CID   32010827.{{cite book}}: Missing or empty |title= (help)
  14. ↑ Gay, R. 2010. Kayentavenator elysiae, a new tetanuran from the early Jurassic of Arizona. Pages 27–43 in Gay, R. Notes on early Mesozoic theropods. Lulu Press (on-demand online press).
  15. 1 2 Lucas, S. G.; Heckert, A. B.; Tanner, L. H. (2005). "Arizona's Jurassic fossil vertebrates and the age of the Glen Canyon Group". In Heckert, A. B.; Lucas, S. G. (eds.). Vertebrate paleontology in Arizona. Bulletin. Vol. 29. Albuquerque, NM: New Mexico Museum of Natural History and Science. pp. 95–104.
  16. 1 2 Jenkins, F. A., Jr., Crompton, A. W., and Downs, W. R. 1983. Mesozoic mammals from Arizona: new evidence in mammalian evolution. Science 222(4629):1233–1235.
  17. 1 2 Jenkins, F. A., Jr. and Shubin, N. H. 1998. Prosalirus bitis and the anuran caudopelvic mechanism. Journal of Vertebrate Paleontology 18(3):495–510.
  18. ↑ Curtis, K., and Padian, K. 1999. An Early Jurassic microvertebrate fauna from the Kayenta Formation of northeastern Arizona: microfaunal change across the Triassic-Jurassic boundary. PaleoBios 19(2):19–37.
  19. 1 2 Luttrell, P. R., and Morales, M. 1993. Bridging the gap across Moenkopi Wash: a lithostratigraphic correlation. Aspects of Mesozoic geology and paleontology of the Colorado Plateau. Pages 111–127 in Morales, M., editor. Museum of Northern Arizona, Flagstaff, AZ. Bulletin 59.
  20. ↑ Hamblin, A. H., and Foster, J. R. 2000. Ancient animal footprints and traces in the Grand Staircase-Escalante National Monument, south-central Utah. Pages 557–568 in Sprinkel, D. A., Chidsey, T. C., Jr., and Anderson, P. B. editors. Geology of Utah's parks and monuments. Utah Geological Association, Salt Lake City, UT. Publication 28.
  21. ↑ Lucas, S. G., and Tanner L. H. 2007. Tetrapod biostratigraphy and biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 244(1–4):242–256.
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