Tatankacephalus
Encyclopedia
Tatankacephalus is a basal genus
of ankylosaurid dinosaur
that lived during the Early Cretaceous
.
Its fossil
has been collected from the Cloverly Formation
(Aptian
-Albian
) of central Montana
during 1996, 1997 and 1998, in the region of the Middle Dome in Wheatland County
. The type species
is T. cooneyorum, described by William L. Parsons and Kirsten Parsons in 2009. The genus name is derived from Oglala
tatanka, "bison
" and Greek kephale, "head", in reference to the rounded head form. The specific name honours the family of John Patrick Cooney. The holotype
is MOR 1073, a partial skull with an estimated total undamaged length of 32 centimetres, lacking the lower jaws. Also some ribs, osteoderm
s and a tooth have been recovered. The front of the snout is missing. The specimen is that of an adult individual.
According to the authors the fossil has not been deformed by compression, allowing to distinguish it from Sauropelta
edwardsorum, another akylosaurian found in the same formation. The head is domed and the eye-sockets are round. A large bone ridge runs transversely across the back of the head. The fossil skull itself no longer had any teeth in it but a single tooth was found, lacking the cingulum
. Two osteoderms were found; one was intact. It has a length of 137 and a width of 115 millimetres. It is hollow and conical.
A cladistic analysis showed that Tatankacephalus was a basal member of the Ankylosauridae and relatively closely related to Gastonia
. Basal traits include the retention of premaxillary teeth in the front of the upper jaws and a skull opening, the lateral temporal fenestra, that was not covered by the skull armour. A new cladistic analysis performed by Thompson et al., 2011 suggests that Tatankacephalus is a basal
nodosaurid.
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 ankylosaurid 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...
that lived during the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
.
Its fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
has been collected from the Cloverly Formation
Cloverly Formation
The Cloverly Formation are Lower Cretaceous strata located in Montana and Wyoming, in the western United States. The term now includes strata that had formerly been called the Dakota Formation in central and southern Wyoming.-Members:...
(Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
-Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
) of central Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
during 1996, 1997 and 1998, in the region of the Middle Dome in Wheatland County
Wheatland County, Montana
-Demographics:As of the census of 2000, there were 2,259 people, 853 households, and 540 families residing in the county. The population density was 2 people per square mile . There were 1,154 housing units at an average density of 1 per square mile...
. 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 T. cooneyorum, described by William L. Parsons and Kirsten Parsons in 2009. The genus name is derived from Oglala
Lakota language
Lakota is a Siouan language spoken by the Lakota people of the Sioux tribes. While generally taught and considered by speakers as a separate language, Lakota is mutually understandable with the other two languages , and is considered by most linguists one of the three major varieties of the Sioux...
tatanka, "bison
Bison
Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
" and Greek kephale, "head", in reference to the rounded head form. The specific name honours the family of John Patrick Cooney. 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...
is MOR 1073, a partial skull with an estimated total undamaged length of 32 centimetres, lacking the lower jaws. Also some ribs, osteoderm
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...
s and a tooth have been recovered. The front of the snout is missing. The specimen is that of an adult individual.
According to the authors the fossil has not been deformed by compression, allowing to distinguish it from Sauropelta
Sauropelta
Sauropelta is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of...
edwardsorum, another akylosaurian found in the same formation. The head is domed and the eye-sockets are round. A large bone ridge runs transversely across the back of the head. The fossil skull itself no longer had any teeth in it but a single tooth was found, lacking the cingulum
Cingulum (tooth)
In dentistry, cingulum refers to an anatomical feature of the anterior teeth . It refers to the portion of the teeth, occurring on the lingual or palatal aspects, that forms a convex protuberance at the cervical third of the anatomic crown. It represents the lingual or palatal developmental lobe...
. Two osteoderms were found; one was intact. It has a length of 137 and a width of 115 millimetres. It is hollow and conical.
A cladistic analysis showed that Tatankacephalus was a basal member of the Ankylosauridae and relatively closely related to Gastonia
Gastonia (dinosaur)
Gastonia is a genus of nodosaurid dinosaur from the Early Cretaceous of North America, around 125 million years ago. Closely related to Polacanthus, it has a sacral shield and large shoulder spikes. It is also the first polacanthine dinosaur to have been mounted for display at the Denver Museum of...
. Basal traits include the retention of premaxillary teeth in the front of the upper jaws and a skull opening, the lateral temporal fenestra, that was not covered by the skull armour. A new cladistic analysis performed by Thompson et al., 2011 suggests that Tatankacephalus is a 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:...
nodosaurid.