''Denversaurus'' (meaning "Denver lizard") is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous (late Maastrichtian) of western North America. Although at one point treated as a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

of '' Edmontonia'' by some

taxonomists In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...

, current research indicates that it is a distinct nodosaurid genus.

Discovery and naming

In 1922, Philip Reinheimer, a collector and technician employed by the Colorado Museum of Natural History, the predecessor of the present Denver Museum of Nature and Science, near the Twito Ranch in

Corson County, South Dakota Corson County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 3,902. Its county seat is McIntosh. The county was named for Dighton Corson, a native of Maine, who came to the Black Hills in 1876, and in ...

discovered the fossil of an ankylosaurian in a Maastrichtian age terrestrial horizon of the Lance Formation. In 1943, American paleontologist

Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. Named after the circus showman P. T. Barnum, he discovered the first documented remains of ''Tyrannosaurus'' during a career ...

referred the find to ''

Edmontonia longiceps ''Edmontonia'' is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation (now the Horseshoe Canyon Formation in Canada) ...

''. In 1988, Robert Thomas Bakker decided to split the genus ''Edmontonia''. The species ''Edmontonia rugosidens'' he made into a separate genus ''Chassternbergia'' and the Denver fossil was named and described as a new genus and species. The type species of this genus was ''Denversaurus schlessmani''. The generic name referred to the Denver Museum of Natural History at Denver, Colorado. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honoured Lee E. Schlessman, a major benefactor of the museum and the founder of the Schlessman Family Foundation.Bakker, R.T. (1988). "Review of the Late Cretaceous nodosauroid Dinosauria: ''Denversaurus schlessmani'', a new armor-plated dinosaur from the Latest Cretaceous of South Dakota, the last survivor of the nodosaurians, with comments on Stegosaur-Nodosaur relationships". ''Hunteria'' 1(3): 1-23.(1988). The fossil the species is based on, the holotype DMNH 468, was discovered in a layer of the late Maastrichtian-age Lance Formation of South Dakota. It consists of a skull, lacking the lower jaws, and a number of osteoderms of the body armour. It is part of the collection of the Denver Museum of Nature and Science after which the genus was named. Bakker referred a second fossil to the species, specimen AMNH 3076, a skull found by Brown and

American Museum of Natural History The American Museum of Natural History (abbreviated as AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. In Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 26 inter ...

paleontologist

Roland T. Bird Roland Thaxter Bird (December 29, 1899 – January 24, 1978) was an American palaeontologist. He is best known for his discovery of fossil trackways of the Paluxy River in Texas, and work with the American Museum of Natural History. Early life ...

at the Tornillo Creek in Brewster County, Texas, in a layer of the poorly dated Upper Cretaceous

Aguja Formation The Aguja Formation is a geological formation in North America, exposed in Texas, United States and Chihuahua and Coahuila in Mexico, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered f ...

, possibly from the Maastrichtian also. Fossil hunters found a nodosaurid skeleton in Niobrara County, Wyoming, nicknamed "Tank", which has been identified as ''Denversaurus''. The specimen contains the lower jaws, parts of the torso and about a hundred osteoderms. It is part of the collection of the

Rocky Mountain Dinosaur Resource Center The Rocky Mountain Dinosaur Resource Center is a fossil museum primarily exhibiting fossil organisms of North America's Late Cretaceous including dinosaurs, pterosaurs, marine reptiles, and fish. The museum includes a fossil preparation lab and a ...

under inventory number BHI 127327. The validity of ''Denversaurus'' was disputed in a 1990 paper on ankylosaurian systematics by Kenneth Carpenter, who noted that Bakker's diagnosis of ''Denversaurus'' was based primarily on Bakker's artistic restoration of the holotype in an uncrushed state. Since DMNH 468 was found crushed, Carpenter assigned ''Denversaurus'' to an ''Edmontonia'' sp., even though he noted its similarity to ''Edmontonia rugosidens''.Carpenter, K. 1990. "Ankylosaur systematics: example using Panoplosaurus and Edmontonia (Ankylosauria: Nodosauridae)", In: Carpenter, K. & Currie, P.J. (eds) Dinosaur Systematics: Approaches and Perspectives, Cambridge University Press, Cambridge, pp. 281-298 A number of workers treated ''Denversaurus'' as synonymous with either ''E. rugosidens'' or ''E. longiceps'', or alternatively a valid species of ''Edmontonia'', an ''Edmontonia schlessmani''.Hunt, A.P. and Lucas, S.G., 1992, "Stratigraphy, Paleontology and age of the Fruitland and Kirkland Formations (Upper Cretaceous), San Juan Basin, New Mexico", ''New Mexico Geological Society Guidebook'', 43rd Field Conference, San Juan Basin, volume 4, p. 217-240Paul, G.S. (2010). The Princeton Field Guide to Dinosaurs, Princeton University Press. In an SVP 2015 abstract, Michael Burns revisited the systematics of latest Cretaceous nodosaurids from the Western Interior. According to Burns, ''Denversaurus'' is a valid taxon based on its phylogenetic position.Burns, ME. Intraspecific Variation in Late Cretaceous Nodosaurids (Ankylosauria: Dinosauria). Journal of Vertebrate Paleontology, Program and Abstracts, 2015, 99–100.

Description

In 2010, American paleontologist Gregory S. Paul estimated the length of ''Denversaurus'' at and its body mass at . American paleontologist

Robert T. Bakker Robert Thomas Bakker (born March 24, 1945) is an American paleontologist who helped reshape modern theories about dinosaurs, particularly by adding support to the theory that some dinosaurs were endothermic (warm-blooded). Along with his mentor J ...

considered ''Denversaurus'' distinct from ''Edmontonia'' and ''Chassternbergia'' in having a skull that was wide at the rear and a more rearward position of the eye sockets. The holotype skull has a length of 496 millimetres and a rear width of 346 millimetres. In the referred specimen AMNH 3076 these proportions are less extreme, measuring 395 millimetres long with a rear width of 220 millimetre. According to American paleontologist Kenneth Carpenter, the greater width of both the holotype and the referred specimen was due to crushing. Vertebrate anatomist and paleontologist Michael Burns in 2015 published an abstract that concluded that ''Denversaurus'' was different from ''Edmontonia'' but similar to '' Panoplosaurus'' in having inflated, convex, cranial sculpturing with visible sulci, or troughs, between individual top skull armour elements, but is distinct from ''Panoplosaurus'' in having a relatively wider snout.

Classification

Bakker in 1988 placed ''Denversaurus'' within an

Edmontoniidae Panoplosaurini (derived from '' Panoplosaurus'', "all shield reptile") is a clade of nodosaurid ankylosaurs from the Cretaceous of North America and South America. The group is defined as the largest clade containing ''Panoplosaurus mirus'', but n ...

, the presumed

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

of the

Nodosauridae Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, wer ...

within a

Nodosauroidea Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, w ...

that would not have been Ankylosauria but the last surviving

Stegosauria Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe, ...

. These hypotheses have not been confirmed by modern cladistic analysis. Today the ''Denversaurus'' material, whether it presents a separate species or is identical to ''E. rugosidens'' or ''E. longiceps'', is considered nodosaurid and ankylosaurian. Paul suggested that it was the direct descendant of ''E. longiceps''. Burns recovered ''Denversaurus'' as the sister species of ''Panoplosaurus''. ''Denversaurus'' is the latest known member of the Thyreophora.

References

{{Taxonbar, from=Q21012043 Nodosaurids Late Cretaceous dinosaurs of North America Lance fauna Maastrichtian life Fossil taxa described in 1988 Taxa named by Robert T. Bakker Hell Creek fauna Paleontology in South Dakota Maastrichtian genus first appearances Maastrichtian genus extinctions Ornithischian genera