Nodocephalosaurus
Encyclopedia
Nodocephalosaurus is a genus
of herbivorous ankylosaurine ankylosaurid
dinosaur
from Upper Cretaceous
(late Campanian
stage) deposits of San Juan Basin
, New Mexico
. The holotype
was recovered from the Late Campanian
De-na-zin Member of the Kirtland Formation
and consists of an incomplete skull
. Nodocephalosaurus (Greek
nodus = knob, kephale = head and sauros = lizard) is a monotypic
genus
, including only the type species
, Nodocephalosaurus kirtlandensis. Dinosaurs like Nodocephalosaurus resembled Asian forms, and may be evidence for Asian dinosaurs migrating to North America in the Late Cretaceous.
s that are bilaterally and symmetrically arranged on the frontonasal region of the skull", and includes deltoid quadratojugal
flange
s and pyramid-shaped squamosal
bosses.
The type description noted the taxon's similarity to the Monogolian ankylosaurids Saichania
chulsanensis and Tarchia
gigantea, and suggested that these three taxa form a clade
within the subfamily Ankylosaurinae. However, Vickaryous and others consider this assignment provisional and list the genus as Ankylosaurinae incertae sedis
.
There is also evidence of a paranasal sinus
cavity in the maxilla
. Sullivan also noted that material previously collected from the Kirtland Formation and assigned to the taxa Euoplocephalus
or Panoplosaurus
might actually represent additional remains of Nodocephalosaurus.
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 herbivorous ankylosaurine ankylosaurid
Ankylosauridae
An ankylosaurid is a member of the Ankylosauridae family of armored dinosaurs that evolved 125 million years ago and became extinct 65 million years ago during the Cretaceous-Tertiary extinction event...
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...
from Upper Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
(late Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
stage) deposits of San Juan Basin
San Juan Basin
The San Juan Basin is a geologic structural basin in the Four Corners region of the Southwestern United States; its main portion covers around , encompassing much of northwestern New Mexico, southwest Colorado, and parts of Arizona and Utah....
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. The holotype
Holotype
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...
was recovered from the Late Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
De-na-zin Member of the Kirtland Formation
Kirtland Formation
The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation...
and consists of an incomplete skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
. Nodocephalosaurus (Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
nodus = knob, kephale = head and sauros = lizard) is a monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
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...
, including only 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...
, Nodocephalosaurus kirtlandensis. Dinosaurs like Nodocephalosaurus resembled Asian forms, and may be evidence for Asian dinosaurs migrating to North America in the Late Cretaceous.
Description and classification
The pattern of cranial ornamentation present in this ankylosaurid "is distinguished by semi-inflated to bulbous, polygonal, cranial osteodermOsteoderm
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...
s that are bilaterally and symmetrically arranged on the frontonasal region of the skull", and includes deltoid quadratojugal
Quadratojugal
The quadratojugal is a small jaw bone that is present in most amphibians, reptiles, and birds, but has been lost in mammals. It is connected to the jugal as well as other bones, though these may vary with species....
flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
s and pyramid-shaped squamosal
Squamosal
The squamosal is a bone of the head of higher vertebrates. It is the principal component of the cheek region in the skull, lying below the temporal series and otic notch and bounded anteriorly by postorbital. Posteriorly, the squamosal articulates with the posterior elements of the palatal complex,...
bosses.
The type description noted the taxon's similarity to the Monogolian ankylosaurids Saichania
Saichania
Saichania is a genus of ankylosaurid dinosaur from the Late Cretaceous period. It was found in the Barun Goyot Formation at Khulsan in the Nemegt Basin, southern Mongolia. It lived during the Campanian. The type species is Saichania chulsanensis.Saichania was described by Teresa Maryańska in 1977,...
chulsanensis and Tarchia
Tarchia
Tarchia is a genus of ankylosaurid dinosaur from the late Cretaceous of Mongolia. It is currently the geologically youngest known of all the Asian ankylosaurid dinosaurs and is represented by five or more specimens, including two complete skulls and one nearly complete postcranial skeleton...
gigantea, and suggested that these three taxa form a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
within the subfamily Ankylosaurinae. However, Vickaryous and others consider this assignment provisional and list the genus as Ankylosaurinae incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
.
There is also evidence of a paranasal sinus
Paranasal sinus
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity , above and between the eyes , and behind the ethmoids...
cavity in 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...
. Sullivan also noted that material previously collected from the Kirtland Formation and assigned to the taxa Euoplocephalus
Euoplocephalus
Euoplocephalus was one of the largest genera of ankylosaurian dinosaurs, at about the size of a small elephant. It is also the ankylosaurian with the best fossil record, so its extensive spiked armor, low-slung body and great club-like tail are well documented.-Description:Among the...
or Panoplosaurus
Panoplosaurus
Panoplosaurus is a genus of nodosaurid dinosaur. It was one of the last known nodosaurids, living during the Late Cretaceous in what is now North America; fossils have been located in Alberta, Canada....
might actually represent additional remains of Nodocephalosaurus.