''Kayentavenator'' (meaning "

Kayenta Kayenta ( nv, ) is a U.S. town which is part of the Navajo Nation and is in Navajo County, Arizona, United States. Established November 13, 1986, the Kayenta Township is the only "township" existing under the laws of the Navajo Nation, making it u ...

hunter") is a genus of small

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

tetanuran Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans (including birds). Tetanurans ar ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

that lived during the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

Period; fossils were recovered from the

Kayenta Formation 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 ...

of northeastern Arizona and were described in 2010.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.

Description

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

specimen of ''K. elysiae'' is a juvenile, as shown by unfused

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

and would have stood about high at the hip. The adult size of ''Kayentavenator'' is unknown. The inclusion of a pubic fenestra is one of the characteristics that

Gay ''Gay'' is a term that primarily refers to a homosexual person or the trait of being homosexual. The term originally meant 'carefree', 'cheerful', or 'bright and showy'. While scant usage referring to male homosexuality dates to the late 1 ...

uses to set ''Kayentavenator'' apart from the contemporaneous, and better known ''

Dilophosaurus ''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 ...

''. As ''Dilophosaurus'' lacks a pubic fenestra as a subadult or an adult,Welles, S. P. (1984). "Dilophosaurus wetherilli (Dinosauria, Theropoda), osteology and comparisons". Palaeontogr. Abt. A 185: 85–180. it is unlikely that it had one during any stage of

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...

Apomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

include an ellipsoid

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that c ...

, the greater

trochanter A trochanter is a tubercle of the femur near its joint with the hip bone. In humans and most mammals, the trochanters serve as important muscle attachment sites. Humans are known to have three trochanters, though the anatomic "normal" includes ...

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 A condyle (;Entry "condyle"
in

Discovery

The only known fossils of ''Kayentavenator'' were excavated by the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham and ...

from the

Navajo Reservation The Navajo Nation ( nv, Naabeehó Bináhásdzo), also known as Navajoland, is a Native Americans in the United States, Native American Indian reservation, reservation in the United States. It occupies portions of northeastern Arizona, northwe ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

. It was briefly described in 2003 and was fully described in 2010 based on a partial

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

, consisting of part of the pelvis, partial hindlimbs, and vertebrae.

Relationships

Timothy Rowe originally assigned the holotype specimen of ''Kayentavenator'' to the

coelophysoid Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the ...

Syntarsus kayentakatae ''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 a ...

'' (now ''Megapnosaurus kayentakatae'' or ''Coelophysis kayentakatae'').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. 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 The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

. A

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis of the remains showed ''Kayentavenator'' to lie outside of

Coelophysidae Coelophysidae is a family of primitive carnivorous theropod dinosaurs. Most species were relatively small in size. The family flourished in the Late Triassic and Early Jurassic periods, and has been found on numerous continents. Many members of C ...

, and was closer to ''

Allosaurus ''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch (Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alluding to ...

''. This would make ''Kayentavenator'' the oldest known

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

, 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.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 It has been surmised that the Kayenta Formation was deposited during the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...

and

Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The Plien ...

stages of the Early Jurassic Period or approximately 199 to 182 million years ago.Padian, K (1997) Glen Canyon Group In: Encyclopedia of Dinosaurs, edited by Currie, P. J., and Padian, K., Academic Press. 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 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.Anonymou ...

. The animals were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes.

Paleofauna

''Kayentavenator'' shared its

paleoenvironment Paleoecology (also spelled palaeoecology) is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescales. As a discipline, paleoecology interacts with, depends on and informs ...

with other dinosaurs, such as several theropods including ''

'', ''

Coelophysis kayentakatae ''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 as ...

'', and the "Shake N Bake" theropod, the basal

sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lon ...

Sarahsaurus ''Sarahsaurus'' is a genus of basal sauropodomorph dinosaur which lived during the Early Jurassic period in what is now northeastern Arizona, United States. Discovery and naming All specimens of ''Sarahsaurus'' were collected from the Lower Ju ...

'', heterodontosaurids, and the armored dinosaurs ''

Scelidosaurus ''Scelidosaurus'' (; with the intended meaning of "limb lizard", from Greek / meaning 'rib of beef' and ''sauros''/ meaning 'lizard')Liddell & Scott (1980). Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. is a gen ...

'' and ''

Scutellosaurus ''Scutellosaurus'' ( ) is a genus of thyreophoran ornithischian dinosaur that lived approximately 196 million years ago during the early part of the Jurassic Period in what is now Arizona, USA. It is classified in Thyreophora, the armoured dino ...

''. The Kayenta Formation has produced the remains of three coelophysoid taxa of different body size, representing the most diverse ceratosaur fauna yet known.Tykoski, R. S., 1998, The Osteology of ''Syntarsus kayentakatae'' and its Implications for Ceratosaurid Phylogeny: Theses, The University of Texas, December 1998. The Kayenta Formation has yielded a small but growing assemblage of organisms. Vertebrates present in the Kayenta Formation at the time of ''Kayentavenator'' included

hybodont Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like chondrichthyans, which existed from the late Devonian to the Late Cretaceous. They form the group of Elasmobranchii closest to neoselachians, the clade of modern shark ...

sharks, indeterminate

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...

, salamanders, the frog ''

Prosalirus ''Prosalirus'' is the name given to a fossilised prehistoric frog found in the Kayenta Formation of Arizona in 1981 by Farish Jenkins.''Geographica''; "Jurassic Frog hops into the record book", National Geographic; August 1996, pg.5. The type, an ...

'', the

caecilia ''Caecilia'' is a genus of amphibians in the family Caeciliidae Caeciliidae is the family of common caecilians. They are found in Central and South America. Like other caecilians, they superficially resemble worms or snakes. Although they ...

n ''

Eocaecilia ''Eocaecilia'' is an extinct genus of gymnophionan amphibian from the early Jurassic Kayenta Formation of Arizona, United States. One species is described, ''Eocaecilia micropodia''. ''Eocaecilia'' shared some characteristics with salamanders a ...

'', the turtle ''

Kayentachelys ''Kayentachelys'' ("Kayenta turtle") 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. History of discovery and significance The e ...

'', a sphenodontian reptile, various lizards, and the

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...

Rhamphinion ''Rhamphinion'' (meaning "beak nape"; Greek ''rhamphos'', "beak" is a common part of "rhamphorhynchoid" names, and the remains of this animal came from the rear of the skull, i.e. "nape" or ''inion'') is a genus of pterosaurs from the Sinemurian ...

''. Also present were the

synapsids Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the Sauropsida, sauropsids, the group that inc ...

Dinnebitodon ''Dinnebitodon'' is an extinct genus of advanced herbivorous cynodonts of the early Jurassic period. It has only been found in the Kayenta Formation in northeastern Arizona. It closely resembles the related genus ''Kayentatherium'' from the sa ...

'', ''

Kayentatherium ''Kayentatherium'' is an extinct genus of tritylodontid cynodonts that lived during the Early Jurassic. It is one of two tritylodonts from the Kayenta Formation of northern Arizona, United States. ''Kayentatherium'' means "Kayenta Beast", and is ...

'', ''

Oligokyphus ''Oligokyphus'' ("few cusps") is an extinct genus of advanced herbivorous cynodonts of the late Triassic to early Jurassic periods. Originally considered to be an early mammal, it is now classified as a Mammaliamorph (nearly a mammal) because ''O ...

'', morganucodontids, the possible early true mammal ''Dinnetherium'', and a haramiyid mammal. Several early

crocodylomorphs Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cr ...

were present including ''

Calsoyasuchus ''Calsoyasuchus'' (meaning " r. KyrilCalsoyas' crocodile") is a genus of crocodylomorph that lived in the Early Jurassic. Its fossilized remains were found in the Sinemurian-Pliensbachian-age Kayenta Formation on Navajo Nation land in Coconino C ...

'', ''

Eopneumatosuchus ''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 on ...

'', ''

Kayentasuchus ''Kayentasuchus'' (meaning "Kayenta Formation crocodile") is a genus of sphenosuchian, a type of basal crocodylomorph, the clade that comprises the crocodilians and their closest kin. It is known from a single skeleton found in rocks of the Si ...

'' and '' Protosuchus''.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.Jenkins, F. A., Jr. and Shubin, N. H. 1998. ''Prosalirus bitis'' and the anuran caudopelvic mechanism. Journal of Vertebrate Paleontology 18(3):495–510. Vertebrate trace fossils from this area included

coprolite A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is de ...

s and the tracks of

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

s, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present.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. Non-vertebrates in this ecosystem included microbial or "algal" limestone,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. freshwater bivalves, freshwater mussels and snails, and

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s.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. The plant life known from this area included trees that became preserved as petrified wood.

References

{{Taxonbar, from=Q1938297 Prehistoric tetanurans Early Jurassic dinosaurs of North America Fossil taxa described in 2010 Paleontology in Arizona Kayenta Formation