Kayentavenator
Encyclopedia
Kayentavenator is a small carnivorous
dinosaur
genus
which lived during the Early Jurassic
Period; fossils were recovered from the Kayenta Formation of northeastern Arizona and were described in 2010.
specimen of K. elysiae is a juvenile, as shown by unfused neural spines
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
. As Dilophosaurus lacks a pubic fenestra as a subadult or an adult, 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.
from the Navajo Reservation in Arizona
. It was described in 2010 based on a partial fossil
skeleton
, consisting of part of the pelvis, partial hindlimbs, and vertebrae.
Gay 2010
kayentakatae (now known as Megapnosaurus). It is unlikely that Kayentavenator is actually cogeneric with Megapnosaurus 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
. A cladistic analysis of the remains showed Kayentavenator to lie outside of Coelophysidae
, and was closer to Allosaurus
. This would make Kayentavenator the oldest known tetanuran from North America. The fragmentary remains of Kayentavenator make this open to further interpretation.
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
which lived during the Early Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
Period; fossils were recovered from the Kayenta Formation of northeastern Arizona and were described in 2010.
Description
The holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen of K. elysiae is a juvenile, as shown by unfused neural spines
Spinous process
The spinous process of a vertebra is directed backward and downward from the junction of the laminae , and serves for the attachment of muscles and ligaments. In animals without an erect stance, the process points upward and may slant forward or backward...
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
Dilophosaurus
Dilophosaurus was a theropod dinosaur from the Sinemurian stage of the Early Jurassic Period, about 193 million years ago. The first specimens were described in 1954, but it was not until over a decade later that the genus received its current name...
. As Dilophosaurus lacks a pubic fenestra as a subadult or an adult, it is unlikely that it had one during any stage of ontogeny
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
. Apomorphies include an ellipsoid acetabulum, the greater trochanter
Trochanter
In human anatomy, the trochanter is a part of the thigh bone. It can refer to:* Greater trochanter* Lesser trochanter* Third trochanter-See also:* Intertrochanteric crest* Intertrochanteric line...
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.
Discovery
The only known fossils of Kayentavenator were excavated by the University of California Museum of PaleontologyUniversity of California Museum of Paleontology
The University of California Museum of Paleontology is a paleontology museum located on the campus of the University of California, Berkeley....
from the Navajo Reservation in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. It was described in 2010 based on a partial fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
, consisting of part of the pelvis, partial hindlimbs, and vertebrae.
Relationships
Timothy Rowe originally assigned the holotype specimen of Kayentavenator to the coelophysoid SyntarsusMegapnosaurus
Megapnosaurus was a dinosaur of the theropod family Coelophysidae, formerly called Syntarsus , living during the Early Jurassic. It was renamed by American entomologist Dr. Michael Ivie , Polish Australian Dr...
kayentakatae (now known as Megapnosaurus). It is unlikely that Kayentavenator is actually cogeneric with Megapnosaurus 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
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
. A cladistic analysis of the remains showed Kayentavenator to lie outside of Coelophysidae
Coelophysidae
The Coelophysidae are 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 was closer to Allosaurus
Allosaurus
Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period . The name Allosaurus means "different lizard". It is derived from the Greek /allos and /sauros...
. This would make Kayentavenator the oldest known tetanuran from North America. The fragmentary remains of Kayentavenator make this open to further interpretation.