''Denversaurus'' (meaning "Denver lizard") is a genus of panoplosaurin

nodosaurid 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 ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

(late

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

) of western North America. Although at one point treated as a junior synonym of ''

Edmontonia ''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 Canad ...

'' 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 Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

Discovery and naming

In 1922,

Philip Reinheimer Philip, also Phillip, is a male given name, derived from the Greek (''Philippos'', lit. "horse-loving" or "fond of horses"), from a compound of (''philos'', "dear", "loved", "loving") and (''hippos'', "horse"). Prominent Philips who populariz ...

, a collector and technician employed by the Colorado Museum of Natural History, the predecessor of the present

Denver Museum of Nature and Science The Denver Museum of Nature & Science is a municipal natural history and science museum in Denver, Colorado. It is a resource for informal science education in the Rocky Mountain region. A variety of exhibitions, programs, and activities help mus ...

, 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 ...

discovered the fossil of an ankylosaurian in a

age terrestrial horizon of the

Lance Formation The Lance (Creek) Formation is a division of Late Cretaceous (dating to about 69 - 66 Ma) rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the lat ...

. 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''. 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 In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

of this genus was ''Denversaurus schlessmani''. The generic name referred to the Denver Museum of Natural History at

Denver, Colorado Denver () is a consolidated city and county, the capital, and most populous city of the U.S. state of Colorado. Its population was 715,522 at the 2020 census, a 19.22% increase since 2010. It is the 19th-most populous city in the United ...

. The specific name 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

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...

. It consists of a skull, lacking the lower jaws, and a number of

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct ...

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 paleontologist Roland T. Bird at the Tornillo Creek in

Brewster County, Texas Brewster County is a county located in the U.S. state of Texas. It is in West Texas and its county seat (and only city) is Alpine. It is one of the nine counties that comprise the Trans-Pecos region, and borders Mexico. Brewster County is th ...

, in a layer of the poorly dated

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

Aguja Formation, possibly from the Maastrichtian also. Fossil hunters found a nodosaurid skeleton in

Niobrara County, Wyoming Niobrara County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 2,467, making it the least populous county in Wyoming. Its county seat is Lusk. Its eastern boundary abuts the west lines of the ...

, 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 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 In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

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 Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

Gregory S. Paul estimated the length of ''Denversaurus'' at and its body mass at . American paleontologist Robert T. Bakker 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 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 ...

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 ''Panoplosaurus'' is a genus of armoured dinosaur from the Late Cretaceous of Alberta, Canada. Few specimens of the genus are known, all from the middle Campanian of the Dinosaur Park Formation, roughly 76 to 75 million years ago. It was first d ...

'' 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 ...

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, w ...

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 Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs ...

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, Euro ...

. These hypotheses have not been confirmed by modern

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

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 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 ...

of ''Panoplosaurus''. ''Denversaurus'' is the latest known member of the

Thyreophora Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. Thyreophorans are characterized by the presence of bod ...

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