Spiclypeus
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''Spiclypeus'' (meaning "spike shield") is an
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
chasmosaurine Chasmosaurinae is a subfamily of ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non- avian dinosaurs, durin ...
ceratopsia Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. ...
n
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 ...
known 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'', the ...
Judith River Formation The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It ...
(late
Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...
stage) of
Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
, United States.


Discovery

In 2000, Bill D. Shipp, a
nuclear physicist Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...
, bought the Paradise Point Ranch near the town of Winifred, in Fergus County. Believing that his land contained fossils, Shipp hired the local veteran fossil collector John C. Gilpatrick to explore the terrain together. On their first trip during an afternoon in September 2005, Shipp found the ''Spiclypeus'' specimen on his land in Montana. He saw a thighbone jutting out of a hillside at the Judith River Breaks. Shipp then hired the amateur paleontologist Joe Small to excavate the fossils. At the cost of several hundred thousand dollars, a road was constructed to allow an excavator to remove the overburden covering the skull of the specimen. In 2007, Small and his team managed to secure all remaining bones. The fossils were prepared in the White River Preparium at Hill City. They were studied by Christopher Ott at the Weis Earth Science Museum in Menasha to provide a scientific description.
Peter Larson Peter Lars Larson (born 1952) is an American fossil expert and president of the Black Hills Institute of Geological Research. He led the team that excavated " Sue", one of the largest and most complete specimen of ''Tyrannosaurus rex'' found to ...
of the
Black Hills Institute The Black Hills Institute of Geological Research, Inc. (BHI) is a private corporation specializing in the excavation and preparation of fossils, as well as the sale of both original fossil material and museum-quality replicas. Founded in 1974 and b ...
made casts of the bones. These were used to make a complete skull reconstruction, missing parts being based on those of ''
Triceratops ''Triceratops'' ( ; ) is a genus of herbivore, herbivorous Chasmosaurinae, chasmosaurine Ceratopsidae, ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous Period (geology), period, about 68 m ...
''. Of this reconstruction again casts were made, sold to several musea. During this time the specimen was informally called "Judith" after the Judith River Formation. In February 2015, paleontologist Jordan Mallon was asked to cooperate in writing a scientific publication naming the
taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
. The specimen was sold to the
Canadian Museum of Nature The Canadian Museum of Nature (french: Musée canadien de la nature; CMN) is a national natural history museum based in Canada's National Capital Region. The museum's exhibitions and public programs are housed in the Victoria Memorial Museum Bui ...
for $350,000, covering Shipp's expenses. ''Spiclypeus'' contains a single species, ''S. shipporum'', first described and named in
2016 File:2016 Events Collage.png, From top left, clockwise: Bombed-out buildings in Ankara following the 2016 Turkish coup d'état attempt; the impeachment trial of Brazilian President Dilma Rousseff; Damaged houses during the 2016 Nagorno-Karabakh ...
by Jordan C. Mallon, Christopher J. Ott, Peter L. Larson, Edward M. Iuliano and David C. Evans. The generic name is derived from
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''spica'', meaning "spike", and ''clypeus'', meaning "shield", in reference to its unique frill ornamented by many large spike-like horn
ossification Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...
s on its margin. The specific name ''shipporum'' honours Dr. Bill and Linda Shipp, the original owners of the type specimen, and their family. ''Spiclypeus'' is known solely from the
holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
CMN 57081 which is housed at the Canadian Museum of Nature in
Ottawa Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the core ...
,
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
. It is represented by a partial disarticulated
skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
(~50% complete), as well as several
postcranial Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...
elements, among them vertebrae, ribs, a left humerus, a left ilium and the left hindlimb. Missing skull elements include the skull roof, the palate, the predentary and the rear of the lower jaws. It was collected from the lower Coal Ridge Member of the
Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...
Judith River Formation several meters above the mid-Judith discontinuity, which dates it to between 76.24±0.18 and 75.21±0.12 million years ago.


Description


Size and distinguishing traits

''Spiclypeus'' has an estimated length of and a weight of about three to four tonnes. ''Spiclypeus'' is unique among
Chasmosaurinae Chasmosaurinae is a subfamily of ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-avian dinosaurs, during ...
in having a wrinkled nose bone contact on the side surface of the rear projection of the
premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
. ''Spiclypeus'' is also unique in having the trait combination of eye-socket horncores that project to above and sideways, all six epiparietals (frill horns) that are fused at their base, first two epiparietals pairs that curl down the frill surface on its front side, and third epiparietal pair that points back and towards the mid-line of the frill. Among other chasmosaurines from the Judith River Formation, ''Spiclypeus'' can be directly distinguished from ''
Judiceratops ''Judiceratops'' ( ; meaning " Judith River horned face") is an extinct horned dinosaur. It lived around 78 million years ago, during the Late Cretaceous Period in what is now Montana, United States. Like other horned dinosaurs, ''Judiceratops ...
'', ''
Medusaceratops ''Medusaceratops'' is an extinct genus of centrosaurine ceratopsian dinosaur known from the Late Cretaceous Judith River Formation (middle Campanian stage) of Montana, northern United States. It contains a single species, ''Medusaceratops lokii'' ...
'' and '' Mercuriceratops''. However, it is morphologically similar to the
dubious Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty ...
ceratopsid species '' Ceratops montanus'' from the Judith River Formation and the dubious chasmosaurine species '' Pentaceratops aquilonius'' from the
Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 76. ...
(located just over the
Canada–United States border The border between Canada and the United States is the longest international border in the world. The terrestrial boundary (including boundaries in the Great Lakes, Atlantic, and Pacific coasts) is long. The land border has two sections: Can ...
and close in age) and in fact all three might represent a single species, which cannot be conclusively tested due to the fragmentary nature of the type specimens of these species.


Skeleton

The skull has a reconstructed length of 167 centimetres. The rostral bone, the core of the upper beak, is strongly hooked. The ascending branch of the praemaxilla has a very rough outer surface, with many deep pits, indicating a strong connection to the nasal bone. The depressions on the outer sides of the praemaxillae are not connected by a perforation, though the separating bone sheath is very thin at one millimetre. The triangular nose horn has a length of 166 millimetres. The
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
has at least twenty-eight positions in the tooth battery, each featuring three to five stacked teeth. The postorbital, or brow, horns are 228 (left) and 246 (right) millimetres long. They strongly project to the side, at an angle of 50° with the midline of the skull. Their points gradually curve to below. The relatively flat skull frill has a triangular profile in top view, with slightly convex sides and diverging rear corners separated by a broad notch on the rear edge. The structure is pierced by large elongated openings, the parietal fenestrae. The frill of ''Spiclypeus'' features a unique pattern of skin ossifications or
osteoderm 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 amp ...
s ornamenting its edge. The side bones of the neck shield, the squamosals, bear episquamosals, with the holotype individual six on the left side and seven on the right side. The front episquamosal projects into the jugal notch between the frill and the cheek elements and forms a triangle six to seven centimetres in length. More to the rear, the episquamosals gradually become wider and lower, but ultimately increase in length again. The rear bones of the frill, the parietals, each carry three epiparietals. In ''Spiclypeus'' these are very wide osteoderms, connected and fused at their bases to form a continuous bone sheath covering almost the entire rear edge of the frill. At the wide notch at the centre of the rear frill edge, this sheath curls to the front, overgrowing the transverse parietal bar behind the fenestrae. The bone flap represents the first and second epiparietal pairs, the "P1s" and "P2s", as is evidenced by the osteoderm points still being visible, those of the first pair pointing to the front near the midline, those of the second pair forming the corners of the flap. The third epiparietals, pointing to behind, together form a pincer-like construction around the notch. At each rear corner of the frill a very large osteoderm is present. As it spans the suture between the squamosal and the parietal, this has been called an epiparietosquamosal or "EPS".


Classification

''Spiclypeus'' was placed in the
Chasmosaurinae Chasmosaurinae is a subfamily of ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-avian dinosaurs, during ...
by Mallon ''et al.'' (2016). It was part of the ''
Chasmosaurus ''Chasmosaurus'' ( ) is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings ( fenestrae) in its frill (Greek ''chasma'' meaning 'opening' or 'hollow' ...
'' instead of the ''
Triceratops ''Triceratops'' ( ; ) is a genus of herbivore, herbivorous Chasmosaurinae, chasmosaurine Ceratopsidae, ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous Period (geology), period, about 68 m ...
'' branch, as a
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 t ...
of a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
formed by ''
Kosmoceratops ''Kosmoceratops'' () is a genus of ceratopsid dinosaur that lived in North America about 76–75.9 million years ago during the Late Cretaceous period. Specimens were discovered in Utah in the Kaiparowits Formation of the Grand Staircase–Esc ...
'' and ''
Vagaceratops ''Vagaceratops'' (meaning "wandering (''vagus'', Latin) horned face", in reference to its close relationship with ''Kosmoceratops'' from Utah) is a genus of herbivorous ceratopsian dinosaur. It is a chasmosaurine ceratopsian which lived during ...
''. Below is the result of their
phylogenetic analysis 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 ...
after the removal of ''
Bravoceratops ''Bravoceratops'' is a genus of large chasmosaurine ceratopsid dinosaur that lived approximately 70 million years ago, and is known from the Late Cretaceous Javelina Formation in what is now Texas, United States. Discovery and naming ''Bravocer ...
'' that groups either with ''Coahuilaceratops'' or in the ''Triceratops'' branch, and ''
Eotriceratops ''Eotriceratops'' (meaning "dawn three-horned face") is a genus of herbivorous ceratopsian dinosaurs which lived in the area of North America during the late Cretaceous period. The only named species is ''Eotriceratops xerinsularis''. Discovery ...
'' that was found to decrease resolution in the ''Triceratops'' branch. Within
Triceratopsini Triceratopsini is a tribe of herbivorous chasmosaurine dinosaurs that lived between the late Campanian to the late Maastrichtian stages of the Cretaceous period, between 74.73 and 66 million years ago. Fossils of these animals have been found in ...
the analysis recovered a
polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tr ...
of six taxa including ''
Ojoceratops ''Ojoceratops'' ( meaning "Ojo Alamo horned face") is a genus of ceratopsian dinosaur which lived in what is now New Mexico, United States. ''Ojoceratops'' fossils have been recovered from strata of the Ojo Alamo Formation (Naashoibito Member), d ...
'', ''
Titanoceratops ''Titanoceratops'' (meaning "titanic horned face") is a controversial genus of herbivorous ceratopsian dinosaur. It was a giant chasmosaurine ceratopsian that lived in the Late Cretaceous period (Campanian stage, about 75 million years agoFowler ...
'', ''
Nedoceratops ''Nedoceratops'' (meaning "insufficient horned face") is a controversial genus of ceratopsid dinosaur from the Late Cretaceous period Lance Formation of North America. It is known only from a single skull discovered in Wyoming. Its status is the ...
'', '' Torosaurus latus'', '' "Torosaurus" utahensis'', and a clade formed by the two species of ''Triceratops''.


Paleobiology

The type specimen of ''Spiclypeus'' appears to have sustained a significant infection in its frill, hypothesised by the authors to have been due to an injury inflicted by a rival of its own species. However, more evidence is needed to determine the cause of the infection. Both the left and right squamosal had received longitudinal injuries. In itself it is not exceptional that adult individuals developed holes in their squamosals, due to bone resorption at an advanced age. However, the perforations in the shield of the ''Spiclypeus'' holotype are different in having a parallel orientation and being located close to the frill edge. It was concluded that they were probably the result of intraspecific combat, the brow horns of an opponent having pierced the shield bone. Another, much more serious, infection was present in the left humerus. The entire lower half of the bone was diseased. Most of the lower joint surface must have been dysfunctional, a large
abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...
having largely eaten away the condyles. The bone had been reworked in reaction, rotating the joint over 90° from its normal orientation. In the middle of the shaft a deep drainage canal had developed, through which the pus ran out. Extensive remodelling of the bone shows that the infection had not been immediately lethal and was perhaps the result of a less virulent
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
or
fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
. The upper part of the humerus also was pathological, showing a large arthritic bone mass. Examination of the specimen's bones also indicates that this specimen was a mature individual at least ten years of age as there were no signs of on-going rapid growth associated with juvenile ceratopsians. The calfbone was sawed to determine the number of "lines of arrested growth" that are usually interpreted as annual growth lines. Seven of these LAGs are present and probably a minimum number of three lines had been obfuscated by later growth processes, resulting in the minimum age estimate of ten years. That the holotype individual had reached a relatively advanced age despite the severe infections, reflects the generally robust ceratopsid build.


See also

*
Timeline of ceratopsian research This timeline of ceratopsian research is a chronological listing of events in the history of paleontology focused on the ceratopsians, a group of herbivorous marginocephalian dinosaurs that evolved parrot-like beaks, bony frills, and, later, spe ...
*
2016 in paleontology Flora Plants Fungi Cnidarians Research * '' Yunnanoascus haikouensis'', previously thought to be a member of Ctenophora, is reinterpreted as a crown-group medusozoan by Han ''et al.'' (2016). * A study on the fossil corals from the Late Tri ...


References

{{Taxonbar, from=Q24091046 Chasmosaurines Late Cretaceous dinosaurs of North America Fossil taxa described in 2016 Paleontology in Montana Ornithischian genera