Kayentasuchus
Encyclopedia
Kayentasuchus is a genus
of sphenosuchia
n, a type of basal
crocodylomorph
, the clade
that comprises the crocodilia
ns and their closest kin. It is known from a single skeleton found in rocks of the Sinemurian
-Pliensbachian
-age Lower Jurassic Kayenta Formation
, northeastern Arizona
.
UCMP
131830, a fragmentary skeleton. UCMP 131830 was known for many years before its description as the "Kayenta Form". It was found in 1983 by James M. Clark. The location was at Willow Springs, 50 kilometres (31.1 mi) northeast of Flagstaff
. The specimen was found in a channel
sandstone
about halfway up the formation, in the "silty facies". Specimens of the turtle Kayentachelys
, the dinosaur
Scutellosaurus
, and tritylodonts
were found in the immediate vicinity a few meters below it.
Kayentasuchus was named in 2002 by Clark and Hans-Dieter Sues
. The type species
is K. walkeri in memory of Alick Walker
, a well-known paleontologist
. Most parts of the skeleton are represented, but are fragmentary, and only the skull, lower jaw, pelvis
, thigh bone
, and bony scutes
received detailed description. Kayentasuchus had a tall, narrow snout and a flattened "skull table" at the back of the skull as in more derived crocodyliforms
. The lower jaw was slender at the tip and curved upward. The teeth were nearly conical, but had distinct unserrated anterior and posterior
edges. Each side of the tip of the upper jaw
had four teeth, while the maxilla
e (main tooth-bearing bone of the upper jaw) and dentaries (tooth-bearing bone of the lower jaw) had twelve or thirteen each. The thigh bones were slender, and there were bony scutes on both the back and belly. The scutes on the upper surface were arranged in two rows running the length of the animal. Clark and Sues performed a phylogenetic analysis
and found Kayentasuchus to have an unresolved position along with several other sphenosuchians, neither closer to true crocodiles or to Sphenosuchus
.
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...
of sphenosuchia
Sphenosuchia
Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Late Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms, which include all living crocodilians.-Stratigraphic...
n, a type of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
crocodylomorph
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
, the clade
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
that comprises the crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns and their closest kin. It is known from a single skeleton found in rocks of the Sinemurian
Sinemurian
In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
-Pliensbachian
Pliensbachian
The Pliensbachian is an age of the geologic timescale or stage in the stratigraphic column. It is part of the Early or Lower Jurassic epoch or series and spans the time between 189.6 ± 1.5 Ma and 183 ± 1.5 Ma . The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.The...
-age Lower Jurassic Kayenta Formation
Kayenta Formation
The Kayenta Formation is a geologic layer 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. This rock formation is particularly prominent in southeastern Utah, where it is seen in the...
, northeastern 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...
.
History and description
Kayentasuchus is based onHolotype
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...
UCMP
University 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....
131830, a fragmentary skeleton. UCMP 131830 was known for many years before its description as the "Kayenta Form". It was found in 1983 by James M. Clark. The location was at Willow Springs, 50 kilometres (31.1 mi) northeast of Flagstaff
Flagstaff, Arizona
Flagstaff is a city located in northern Arizona, in the southwestern United States. In 2010, the city's population was 65,870. The population of the Metropolitan Statistical Area was at 134,421 in 2010. It is the county seat of Coconino County...
. The specimen was found in a channel
Channel (geography)
In physical geography, a channel is the physical confine of a river, slough or ocean strait consisting of a bed and banks.A channel is also the natural or human-made deeper course through a reef, sand bar, bay, or any shallow body of water...
sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
about halfway up the formation, in the "silty facies". Specimens of the turtle Kayentachelys
Kayentachelys
Kayentachelys is an extinct genus of cryptodire turtle from the Early Jurassic Kayenta Formation of northern Arizona. Kayentachelys was approximately wide and in length. It lived in an environment dominated by streams and dunes....
, the 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...
Scutellosaurus
Scutellosaurus
Scutellosaurus is a genus of herbivorous dinosaur that lived in North America around 200 to 196 million years ago, in the Early Jurassic times....
, and tritylodonts
Tritylodontidae
Tritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont...
were found in the immediate vicinity a few meters below it.
Kayentasuchus was named in 2002 by Clark and Hans-Dieter Sues
Hans-Dieter Sues
Hans-Dieter Sues is a German-born paleontologist who is Senior Scientist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. He received his education at Johannes Gutenberg-Universität Mainz , University of Alberta, and...
. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is K. walkeri in memory of Alick Walker
Alick Walker
Alick Donald Walker was a British palaeontologist, after whom the Alwalkeria genus of dinosaur is named....
, a well-known paleontologist
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
. Most parts of the skeleton are represented, but are fragmentary, and only the skull, lower jaw, pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
, thigh bone
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, and bony scutes
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
received detailed description. Kayentasuchus had a tall, narrow snout and a flattened "skull table" at the back of the skull as in more derived crocodyliforms
Crocodyliformes
Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians."In 1988, Michael J. Benton and James M. Clark argued that all traditional names for well-known groups of animals should be restricted to their crown clades, that is, used only for...
. The lower jaw was slender at the tip and curved upward. The teeth were nearly conical, but had distinct unserrated anterior and posterior
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
edges. Each side of the tip of the upper jaw
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
had four teeth, while the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e (main tooth-bearing bone of the upper jaw) and dentaries (tooth-bearing bone of the lower jaw) had twelve or thirteen each. The thigh bones were slender, and there were bony scutes on both the back and belly. The scutes on the upper surface were arranged in two rows running the length of the animal. Clark and Sues performed a phylogenetic analysis
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
and found Kayentasuchus to have an unresolved position along with several other sphenosuchians, neither closer to true crocodiles or to Sphenosuchus
Sphenosuchus
Sphenosuchus is an extinct genus of sphenosuchian from the Elliot Formation of South Africa, discovered and described early in the 20th century. The skull is excellently preserved but other than elements of the forelimb and isolated parts of the hind limb, the Sphenosuchus material is incomplete...
.