Kayentavenator

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Kayentavenator
Temporal range: Early Jurassic, 189  Ma
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Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Tetanurae
Genus:† Kayentavenator
Gay, 2010
Species:
†K. elysiae
Binomial name
†Kayentavenator elysiae
Gay, 2010

Kayentavenator (meaning "Kayenta hunter") 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. [1]

Description

The holotype specimen of K. elysiae is a juvenile, as shown by unfused neural spines [1] and would have stood about 0.5 metres (1.6 ft) high at the hip. The adult size of Kayentavenator is unknown. The inclusion of a pubic fenestra is one of the characteristics that Gay uses to set Kayentavenator apart from the contemporaneous, and better known Dilophosaurus . [1] As Dilophosaurus lacks a pubic fenestra as a subadult or an adult, [2] it is unlikely that it had one during any stage of ontogeny. Apomorphies include an ellipsoid acetabulum, the greater trochanter and the head of the femur having been fused, a mediodistal crest that extends 50% of the length of the femur, as well as a prominent accessory condyle on the medial femoral condyle, a groove in dorsal surface of the femoral head that extends out from the centerline of the body, and highly constricted ("waisted") caudal vertebra centra. [1]

Discovery

The only known fossils of Kayentavenator were excavated by the University of California Museum of Paleontology from the Navajo Reservation in Arizona. It was briefly described in 2003 [3] and was fully described in 2010 based on a partial fossil skeleton, consisting of part of the pelvis, partial hindlimbs, and vertebrae. [1]

Cladogram of Theropods (Gay 2010 [1] )

Classification

Timothy Rowe originally assigned the holotype specimen of Kayentavenator to the coelophysoid Syntarsus kayentakatae (now Megapnosaurus kayentakatae or Coelophysis kayentakatae). [4] It is unlikely that Kayentavenator is actually congeneric with Megapnosaurus kayentakatae due to the number of tetanuran characters that Kayentavenator possesses and M. kayentakatae lacks, such as the pubic fenestra and a sharp ridge on the medial side of the tibia. [1] A cladistic analysis of the remains showed Kayentavenator to lie outside of Coelophysidae, and was closer to Allosaurus . [1] This would make Kayentavenator the oldest known tetanuran from North America. The fragmentary remains of Kayentavenator make this open to further interpretation.

Paleoecology

Habitat

The only known specimen of Kayentavenator, UCMP V128659, was recovered from the Silty Facies Member of the Kayenta Formation, in northeastern Arizona. A definitive radiometric dating of this 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. [5] It has been surmised that the Kayenta Formation was deposited during the Sinemurian and Pliensbachian stages of the Early Jurassic Period or approximately 199 to 182 million years ago. [6] 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 period, 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. [7] The animals were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes.

Paleofauna

Kayentavenator shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus , Coelophysis kayentakatae , and the "Shake N Bake" theropod, the basal sauropodomorph Sarahsaurus , [8] heterodontosaurids, and the armored dinosaurs Scelidosaurus and Scutellosaurus . The Kayenta Formation has produced the remains of three coelophysoid taxa of different body size, representing the most diverse ceratosaur fauna yet known. [9] The Kayenta Formation has yielded a small but growing assemblage of organisms. [10] Vertebrates present in the Kayenta Formation at the time of Kayentavenator 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, [11] the possible early true mammal Dinnetherium, and a haramiyid mammal. Several early crocodylomorphs were present including Calsoyasuchus , Eopneumatosuchus , Kayentasuchus and Protosuchus . [10] [11] [12] [13]

Vertebrate trace fossils from this area included coprolites [14] and the tracks of therapsids, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present. [15] Non-vertebrates in this ecosystem included microbial or "algal" limestone, [14] freshwater bivalves, freshwater mussels and snails, [7] and ostracods. [16] The plant life known from this area included trees that became preserved as petrified wood. [12]

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 186 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. Fossil 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.

<i>Coelophysis</i> Genus of theropod dinosaurs from the late Triassic

Coelophysis is a genus of coelophysid theropod dinosaur that lived approximately 215 to 208.5 million years ago during the Late Triassic period from the middle to late Norian age in what is now the southwestern United States. Megapnosaurus was once considered to be a species within this genus, but this interpretation has been challenged since 2017 and the genus Megapnosaurus is now considered valid.

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).

Oligokyphus is an extinct genus of herbivorous tritylodontid cynodont known from the Late Triassic to Early Jurassic of Europe, Asia and North America.

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

Segisaurus is a genus of small coelophysid theropod dinosaur, that measured approximately 1 metre in length. The only known specimen was discovered in early Jurassic strata in Tsegi Canyon, Arizona, for which it was named. Segisaurus is the only dinosaur to have ever been excavated from the area.

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

Liliensternus is an extinct genus of basal neotheropod dinosaur that lived approximately 210 million years ago during the latter part of the Triassic Period in what is now Germany. Liliensternus was a moderate-sized, bipedal, ground-dwelling carnivore, that could grow up to 5.15 m (16.9 ft) long. It is the best represented Triassic theropod from Europe and one of the largest known.

<span class="mw-page-title-main">Navajo Sandstone</span> Geologic formation in the southwestern United States

The Navajo Sandstone is a geological formation in the Glen Canyon Group that is spread across the U.S. states of southern Nevada, northern Arizona, northwest Colorado, and Utah as part of the Colorado Plateau province of the United States.

<i>Sinosaurus</i> Genus of dinosaurs

Sinosaurus is an extinct genus of theropod dinosaur which lived during the Early Jurassic Period. It was a bipedal carnivore approximately 5.5 metres (18 ft) in length and 300 kilograms (660 lb) in body mass. Fossils of the animal were found at the Lufeng Formation, in the Yunnan Province of China.

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

Zupaysaurus is an extinct genus of early theropod dinosaur living during the Norian stage of the Late Triassic in what is now Argentina. Fossils of the dinosaur were found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. Although a full skeleton has not yet been discovered, Zupaysaurus can be considered a bipedal predator, up to 4 metres (13 ft) long. It may have had two parallel crests running the length of its snout.

<span class="mw-page-title-main">Glen Canyon Group</span> Group of geologic formations in the Colorado Plateau, USA

The Glen Canyon Group is a geologic group of formations that is spread across the U.S. states of Nevada, Utah, northern Arizona, north west New Mexico and western Colorado. It is called the Glen Canyon Sandstone in the Green River Basin of Colorado and Utah.

<span class="mw-page-title-main">Wingate Sandstone</span> Geologic formation across the Colorado Plateau, USA

The Wingate Sandstone is a geologic formation in the Glen Canyon Group of the Colorado Plateau province of the United States which crops out in northern Arizona, northwest Colorado, Nevada, and Utah.

<span class="mw-page-title-main">Kayenta Formation</span> Jurassic sandstone formation of the southwestern United States

The Kayenta Formation is a geological formation in the Glen Canyon Group that is spread across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah. Traditionally has been suggested as Sinemurian-Pliensbachian, but more recent dating of detrital zircons has yielded a depositional age of 183.7 ± 2.7 Ma, thus a Pliensbachian-Toarcian age is more likely. A previous depth work recovered a solid "Carixian" age from measurements done in the Tenney Canyon. More recent works have provided varied datations for the layers, with samples from Colorado and Arizona suggesting 197.0±1.5-195.2±5.5 Ma, while the topmost section is likely Toarcian or close in age, maybe even recovering terrestrial deposits coeval with the Toarcian Oceanic Anoxic Event. This last age asignation also correlated the Toarcian Vulcanism on the west Cordilleran Magmatic Arc, as the number of grains from this event correlate with the silt content in the sandstones of the upper layers.

Eopneumatosuchus is an extinct genus of basal crocodyliform. Fossils have been found from two localities within the Kayenta Formation of Arizona. Both localities are around 20 miles southeast of the Grand Canyon and in close proximity to one another. The localities probably date back to the Early Jurassic, most likely during the Sinemurian stage.

<span class="mw-page-title-main">Neotheropoda</span> Clade of theropods

Neotheropoda is a clade that includes coelophysoids and more advanced theropod dinosaurs, and is the only group of theropods that survived the Triassic–Jurassic extinction event. All neotheropods became extinct by the end of the Early Jurassic except for Averostra.

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>Sarahsaurus</i> Extinct genus of dinosaurs

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

<span class="mw-page-title-main">Averostra</span> Clade of dinosaurs

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs, namely Ceratosauria and Tetanurae, and represent the only group of post-Early Jurassic theropods. Both survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians, megaraptorans an incertae sedis group within Tetanurae, and two groups of tetanurans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of Maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

<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 Megapnosaurus is now considered valid.

<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. It was originally named Syntarsus kayentakatae, but the genus Syntarsus was found to be preoccupied by a Colydiine beetle, so it was moved to the genus Megapnosaurus, and then to Coelophysis. A recent reassessment suggests that this species may require a new genus name.

Shuangbaisaurus is genus of theropod dinosaur, possibly a junior synonym of Sinosaurus. It lived in the Early Jurassic of Yunnan Province, China, and is represented by a single species, S. anlongbaoensis, known from a partial skull. Like the theropods Dilophosaurus and Sinosaurus,Shuangbaisaurus bore a pair of thin, midline crests on its skull. Unusually, these crests extended backwards over the level of the eyes, which, along with the unusual orientation of the jugal bone, led the describers to name it as a new genus. However, Shuangbaisaurus also possesses a groove between its premaxilla and maxilla, a characteristic which has been used to characterize Sinosaurus as a genus. Among the two morphotypes present within the genus Sinosaurus, Shuangbaisaurus more closely resembles the morphotype that is variably treated as a distinct species, S. sinensis, in its relatively tall skull.

References

  1. 1 2 3 4 5 6 7 8 Gay, Robert. 2010. "Kayentavenator elysiae", a new tetanuran from the Early Jurassic of Arizona" In: Notes on Early Mesozoic Theropods. Lulu Press. p. 27-43. ISBN   978-0-557-46616-0
  2. ↑ Welles, S. P. (1984). "Dilophosaurus wetherilli (Dinosauria, Theropoda), osteology and comparisons". Palaeontogr. Abt. A 185: 85–180.
  3. ↑ Gay, Robert. 2003. A new theropod from the Lower Jurassic Kayenta Formation of Arizona. Unpublished undergraduate thesis, Northern Arizona University, Flagstaff, Arizona.
  4. ↑ Rowe, T. 1989. A new species of the theropod dinosaur Syntarsus from the Early Jurassic Kayenta Formation of Arizona. Journal of Vertebrate Paleontology. vol. 9 no. 2. p. 125-136.
  5. ↑ 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
  6. ↑ Padian, K (1997) Glen Canyon Group In: Encyclopedia of Dinosaurs, edited by Currie, P. J., and Padian, K., Academic Press.
  7. 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.
  8. ↑ Rowe, T. B., Sues, H.-D., and Reisz, R. R. 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.
  9. ↑ Tykoski, R. S., 1998, The Osteology of Syntarsus kayentakatae and its Implications for Ceratosaurid Phylogeny: Theses, The University of Texas, December 1998.
  10. 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.
  11. 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.
  12. 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.
  13. ↑ 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.
  14. 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.
  15. ↑ 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.
  16. ↑ 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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