Triceratops is a
genusIn 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
ceratopsidCeratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
dinosaurDinosaurs 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...
which lived during the
late MaastrichtianThe Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage of the Late
CretaceousThe 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...
Period, around 68 to 65 million years ago (Mya) in what is now
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It was one of the last dinosaur genera to appear before the great
Cretaceous–Paleogene extinction eventThe Cretaceous–Paleogene extinction event, formerly named and still commonly referred to as the Cretaceous-Tertiary extinction event, occurred approximately 65.5 million years ago at the end of the Maastrichtian age of the Cretaceous period. It was a large-scale mass extinction of animal and plant...
. The term
Triceratops, which literally means "three-horned face," is derived from the
GreekAncient 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...
τρί- (
tri-) meaning "three", κέρας (
kéras) meaning "horn", and ὤψ (
ops) meaning "face".
Bearing a large bony
frillNeck frill is the popular term for the relatively extensive margin seen on the back of the heads of reptiles with either a bony support such as those present on the skulls of dinosaurs of the suborder Marginocephalia or a cartilaginous one as in the Frill-necked Lizard...
and three
hornsA horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...
on its large four-legged body, and conjuring similarities with the modern
rhinocerosRhinoceros , also known as rhino, is a group of five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia....
,
Triceratops is one of the most recognizable of all dinosaurs and the best known ceratopsid. It shared the landscape with and was
preyed uponIn ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
by the fearsome
TyrannosaurusTyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
, though it is less certain that the two did battle in the manner often depicted in traditional museum displays and popular images.
The exact placement of the
Triceratops genus within the ceratopsid group has been debated by
paleontologistsPaleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
. Two
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
,
T. horridus and
T. prorsus, are considered valid although many other species have been named. Recent research suggests that the contemporaneous
TorosaurusTorosaurus is a genus of ceratopsid dinosaur that lived during the late Cretaceous period , between 70 and 65 million years ago. It possessed one of the largest skulls of any known land animal. The frilled skull reached in length...
, a ceratopsid long regarded as a separate genus, actually represents
Triceratops in its mature form.
Triceratops has been documented by numerous remains collected since the genus was first described in 1889, including at least one complete individual skeleton. Paleontologist John Scannella observed: "It is hard to walk out into the
Hell Creek FormationThe Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...
and not stumble upon a
Triceratops weathering out of a hillside." Forty-seven complete or partial skulls were discovered in just that area during the decade 2000–2010. Specimens representing life stages from hatchling to adult have been found.
The function of the frills and three distinctive facial horns has long inspired debate. Traditionally these have been viewed as defensive weapons against predators. More recent theories, noting the presence of blood vessels in the skull bones of ceratopsids, find it more probable that these features were primarily used in identification,
courtshipIn biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
and dominance displays, much like the
antlerAntlers are the usually large, branching bony appendages on the heads of most deer species.-Etymology:Antler originally meant the lowest tine, the "brow tine"...
s and horns of modern
reindeerThe reindeer , also known as the caribou in North America, is a deer from the Arctic and Subarctic, including both resident and migratory populations. While overall widespread and numerous, some of its subspecies are rare and one has already gone extinct.Reindeer vary considerably in color and size...
,
mountain goatThe Mountain Goat , also known as the Rocky Mountain Goat, is a large-hoofed mammal found only in North America. Despite its vernacular name, it is not a member of Capra, the genus of true goats...
s, or
rhinoceros beetleThe Rhinoceros Beetles or Rhino Beetles are a subfamily of the scarab beetle family . Other common names – some for particular groups of rhino beetles – are for example Hercules beetles, unicorn beetles or horn beetles...
s. The theory finds additional support if
Torosaurus represents the mature form of
Triceratops, as this would mean the frill also developed holes (fenestrae) as individuals reached maturity, rendering the structure more useful for display than defense.
Description
Individual
Triceratops are estimated to have reached about 7.9 to 9.0
mThe metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...
(26.0–29.5 ft) in length, 2.9 to 3.0 m (9.5–9.8 ft) in height, and 6.1–12.0
tonneThe tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s (13,000–26,000
lbThe pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
) in
weightIn science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...
. The most distinctive feature is their large
skullThe 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...
, among the largest of all land animals. The largest known skull (specimen
BYUBrigham Young University is a private university located in Provo, Utah. It is owned and operated by The Church of Jesus Christ of Latter-day Saints , and is the United States' largest religious university and third-largest private university.Approximately 98% of the university's 34,000 students...
12183) is estimated to have been 2.5 metres (8.2 ft) in length when complete, and could reach almost a third of the length of the entire animal. It bore a single horn on the snout, above the
nostrilA nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s, and a pair of horns approximately 1 m (3 ft) long, with one above each eye. To the rear of the skull was a relatively short, bony frill, adorned with epoccipitals in some specimens. Most other ceratopsids had large
fenestraeFenestræ is a Latin word that means "window".* In histology, fenestræ are small pores in endothelial cells that allow for rapid exchange of molecules between sinusoid blood vessels and surrounding tissue...
in their frills, while those of
Triceratops were noticeably solid.
The skin of
Triceratops was unusual compared to other dinosaurs. Skin impressions from an as-yet undescribed specimen show that some species may have been covered in bristle-like structures, similar to the more primitive ceratopsian
PsittacosaurusPsittacosaurus is a genus of psittacosaurid ceratopsian dinosaur from the Early Cretaceous Period of what is now Asia, about 130 to 100 million years ago. It is notable for being the most species-rich dinosaur genus...
.
Limbs
Triceratops species possessed a sturdy build, with strong limbs and short three-hoofed hands and four-hoofed feet. Although certainly
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al, the posture of these dinosaurs has long been the subject of some debate. Originally, it was believed that the front legs of the animal had to be sprawling at angles from the
thoraxThe thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
, in order to better bear the weight of the head. This stance can be seen in paintings by
Charles KnightCharles Robert Knight was an American artist best known for his influential paintings of dinosaurs and other prehistoric animals...
and
Rudolph ZallingerRudolph Franz Zallinger was an American-based artist notable for his mural The Age of Reptiles at Yale's Peabody Museum of Natural History and for the popular illustration known as March of Progress , one of the world's most recognizable scientific images.-Biography:Zallinger was born in Irkutsk,...
. However,
ichnologicalIchnology is the branch of geology that deals with traces of organismal behavior, such as burrows and footprints. It is generally considered as a branch of paleontology; however, only one division of ichnology, paleoichnology, deals with trace fossils, while neoichnology is the study of modern traces...
evidence in the form of
trackwaysA fossil trackway is a type of trace fossil, a trackway made by an organism. Many fossil trackways were made by dinosaurs, early tetrapods, and other quadrupeds and bipeds on land...
from horned dinosaurs, and recent reconstructions of skeletons (both physical and digital) seem to show that
Triceratops and other ceratopsids maintained an upright stance during normal locomotion, with the elbows flexed and slightly bowed out, in an intermediate state between fully upright and fully sprawling (as in the modern rhinoceros).
The hands and forearms of
Triceratops retained a fairly primitive structure compared to other quadrupedal dinosaurs such as
thyreophoraThe Thyreophora were a subgroup of the ornithischian dinosaurs...
ns and many
sauropodsSauropoda , or the sauropods , are an infraorder of saurischian dinosaurs. They had long necks, long tails, small heads , and thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land...
. In those two groups, the forelimbs of quadrupedal species were usually rotated so that the hands faced forward with palms backward ("pronated") as the animals walked. However,
Triceratops, like other ceratopsians and the related quadrupedal ornithopods, walked with most of their fingers pointing out and away from the body, the primitive condition for dinosaurs also retained by bipedal forms like the
theropodsTheropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
. In
Triceratops, the weight of the body was carried by only the first three fingers of the hand, while the third and fourth were vestigial and lacked claws or hooves.
Classification
Triceratops is the best known genus of the
CeratopsidaeCeratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
, a family of large North American
horned dinosaursCeratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. The earliest known ceratopsian, Yinlong downsi, lived between 161.2 and 155.7...
. The exact location of
Triceratops among the ceratopsians has been debated over the years. Confusion stemmed mainly from the combination of short, solid frills (similar to that of
CentrosaurinaeThe Centrosaurinae is a subfamily of ceratopsid dinosaurs named by paleontologist Lawrence Lambe, in 1915, with Centrosaurus as the type genus...
), and the long brow horns (more akin to
CeratopsinaeCeratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
, also known as Chasmosaurinae). In the first overview of horned dinosaurs,
R. S. LullRichard Swann Lull was an American paleontologist from the early 20th century, active at Yale University, who is largely remembered now for championing a Pre-Neo-Darwinian Synthesis view of evolution, whereby mutation could unlock mysterious genetic drives that, over time, would lead populations...
hypothesized two lineages, one of
MonocloniusMonoclonius was a ceratopsian dinosaur from the Judith River Formation of Late Cretaceous Montana and Canada. It is often confused with Centrosaurus, a similar genus of ceratopsian . Monoclonius was described by Edward Drinker Cope in 1876...
and
CentrosaurusCentrosaurus is a genus of herbivorous ceratopsian dinosaurs from the late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation and uppermost Oldman Formation, dating from 76.5 to 75.5 million years ago....
leading to
Triceratops, the other with
CeratopsCeratops is a dubious genus of ceratopsian dinosaur which lived during the Late Cretaceous. Its fossils have been found in Montana. Although poorly known, Ceratops is important in the history of dinosaurs, since it is the type species for which both Ceratopsia and Ceratopsidae are named...
and
TorosaurusTorosaurus is a genus of ceratopsid dinosaur that lived during the late Cretaceous period , between 70 and 65 million years ago. It possessed one of the largest skulls of any known land animal. The frilled skull reached in length...
, making
Triceratops a centrosaurine as the group is understood today. Later revisions supported this view, formally describing the first, short-frilled group as Centrosaurinae (including
Triceratops), and the second, long-frilled group as Chasmosaurinae.
In 1949,
C. M. SternbergCharles M. Sternberg was an American-Canadian fossil collector and paleontologist, son of Charles Hazelius Sternberg.Late in his career, he collected and described Pachyrhinosaurus, Brachylophosaurus, Parksosaurus and Edmontonia...
was the first to question this and favoured instead that
Triceratops was more closely related to
ArrhinoceratopsArrhinoceratops is a genus of ceratopsian dinosaur. The name was coined as its original describer concluded it had no nose-horn, however further analysis revealed this not to be the case...
and
ChasmosaurusChasmosaurus is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings in its frill . With a length of and a weight of , Chasmosaurus was a ceratopsian of average size...
based on skull and horn features, making
Triceratops a ceratopsine (chasmosaurine of his usage) genus. However, he was largely ignored with
John OstromJohn H. Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s, when he demonstrated that dinosaurs are more like big non-flying birds than they are like lizards , an idea first proposed by Thomas Henry Huxley in the 1860s, but which had garnered...
, and later David Norman, both placing
Triceratops within Centrosaurinae.
Subsequent discoveries and analyses upheld Sternberg's view on the position of
Triceratops, with Lehman defining both subfamilies in 1990 and diagnosing
Triceratops as ceratopsine (chasmosaurine of his usage) on the basis of several morphological features. In fact, it fits well into the ceratopsine subfamily, apart from its one feature of a shortened frill. Further research by
Peter DodsonPeter Dodson is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs and sauropods, and is a co-editor of The Dinosauria, widely considered the...
, including a 1990
cladisticCladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
analysis and a 1993 study using RFTRA (resistant-fit theta-rho analysis), a
morphometric techniqueMorphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...
which systematically measures similarities in skull shape, reinforces
Triceratops placement in the ceratopsine subfamily.
This classification found additional support in 2010 from John Scannella and Jack Horner at the Museum of the Rockies (Bozeman, Montana). After examining 38 skulls from the Hell Creek formation, Scanella and Horner concluded that the mature form of Triceratops
did not even have a shortened frill. The specimens long classified as Triceratops
, they argued, represented juvenile and young adult individuals while mature individuals had been incorrectly assigned to a separate genus, Torosaurus
. It was already known that the frills of Triceratops
grew progressively longer as individuals matured; Scanella and Horner said their findings showed that this growth could culminate in the extended, fenestrated frill associated with Torosaurus
. With the name Triceratops
taking historical priority, they announced that references to the genus Torosaurus
would be eliminated from Museum of the Rockies exhibits.
Use in phylogenetics
In phylogenetic taxonomyIn biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
, the genus has been used as a reference point in the definition of Dinosauria; Dinosaurs have been designated as all descendants of the most recent common ancestorIn genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
of Triceratops
and NeornithesModern birds are the most recent common ancestor of all living birds and all its descendants.Modern birds are characterised by feathers, a beak with no teeth , the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton...
(i.e. modern birdBirds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s). Furthermore, the bird-hipped dinosaurs, OrnithischiaOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
, have been designated as all dinosaurs with a more recent common ancestor to Triceratops
than modern birds.
Discovery and identification
The first named specimen now attributed to Triceratops
is a pair of brow horns attached to a skull roof, found near Denver, ColoradoThe City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains...
in the spring of 1887. This specimen was sent to Othniel Charles MarshOthniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
, who believed that the formationA formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
from which it came dated from the PlioceneThe Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
, and that the bones belonged to a particularly large and unusual bisonMembers of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
, which he named Bison alticornis
. He realized that there were horned dinosaurs by the next year, which saw his publication of the genus CeratopsCeratops is a dubious genus of ceratopsian dinosaur which lived during the Late Cretaceous. Its fossils have been found in Montana. Although poorly known, Ceratops is important in the history of dinosaurs, since it is the type species for which both Ceratopsia and Ceratopsidae are named...
from fragmentary remains, but he still believed B. alticornis
to be a Pliocene mammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
. It took a third and much more complete skull to change his mind. The specimen, collected in 1888 by John Bell HatcherJohn Bell Hatcher was an American paleontologist and fossil hunter best known for discovering Torosaurus.-Biography:...
from the Lance FormationThe Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
of WyomingWyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, was initially described as another species of Ceratops
. After reflection, however, Marsh changed his mind and gave it the generic name Triceratops
, accepting his Bison alticornis
as another species of Ceratops
(it would later be added to Triceratops
). The sturdy nature of the animal's skull has ensured that many examples have been preserved as fossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s, allowing variations between speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
and individuals to be studied. Triceratops
remains have subsequently been found in the American states of MontanaMontana 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,...
and South DakotaSouth Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
(in addition to Colorado and Wyoming), and in the CanadianCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
provinces of SaskatchewanSaskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
and AlbertaAlberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
.
Species
Within the first decades after Triceratops
was described, various skulls were collected, which varied to a lesser or greater degree from the original Triceratops
, named T. horridus
by Marsh (from the LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
horridus
; "rough, rugose", suggesting the roughened texture of those bones belonging to the type specimen, later identified as an aged individual). This variation is unsurprising, given that Triceratops skulls are large three-dimensional objects, coming from individuals of different ages and both sexes, and which were subjected to different amounts and directions of pressure during fossilization. Discoverers would name these as separate species (listed below), and came up with several phylogenetic schemes for how they were related to each other.
In the first attempt to understand the many species, Lull found two groups, although he did not say how he distinguished them: one composed of T. horridus
, T. prorsus
, and T. brevicornus
; the other of T. elatus
and T. calicornis
. Two species (T. serratus
and T. flabellatus
) stood apart from these groups. By 1933, and his revision of the landmark 1907 Hatcher-Marsh-Lull monographA monograph is a work of writing upon a single subject, usually by a single author.It is often a scholarly essay or learned treatise, and may be released in the manner of a book or journal article. It is by definition a single document that forms a complete text in itself...
of all known ceratopsians, he retained his two groups and two unaffiliated species, with a third lineage of T. obtusus
and T. hatcheri
that was characterized by a very small nasal horn. T. horridus
-T. prorsus
-T. brevicornus
was now thought to be the most conservative lineage, with an increase in skull size and a decrease in nasal horn size, and T.-elatus
-T. calicornis
was defined by large brow horns and small nasal horn. C. M. Sternberg made one modification, adding T. eurycephalus
and suggesting that it linked the second and third lineages closer together than they were to the T. horridus
lineage. This pattern was followed until the major studies of the 1980s and 1990s.
With time, however, the idea that the differing skulls might be representative of individual variation within one (or two) species gained popularity. In 1986, Ostrom and Wellnhofer published a paper in which they proposed that there was only one species, Triceratops horridus
. Part of their rationale was that generally there are only one or two species of any large animal in a region (modern examples being the elephant and the giraffeThe giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...
in modern Africa). To their findings, Lehman added the old Lull-Sternberg lineages combined with maturity and sexual dimorphismSexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, suggesting that the T. horridus
-T. prorsus
-T. brevicornus
lineage was composed of females, the T.calicornis
-T.elatus
lineage was made up of males, and the T. obtusus
-T. hatcheri
lineage was of pathologicPathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
old males. His reasoning was that males had taller, more erect horns and larger skulls, and females had smaller skulls with shorter, forward-facing horns.
These findings, however, were contested a few years later by Catherine Forster, who reanalyzed Triceratops
material more comprehensively and concluded that the remains fell into two species, T. horridus
and T. prorsus
, although the distinctive skull of T.
("Nedoceratops
") hatcheri
differed enough to warrant a separate genus. She found that T. horridus
and several other species belonged together, and T. prorsus
and T. brevicornus
stood alone, and since there were many more specimens in the first group, she suggested that this meant the two groups were two species. It is still possible to interpret the differences as representing a single species with sexual dimorphism.
In 2009, John Scannella and Denver Fowler supported the separation of T. prorsus
and T. horridus
, and noted that the two species are also separated stratigraphically within the Hell Creek Formation, indicating that they did not live together at the same time.
Valid species
T. horridus
(Marsh, 1889) (originally CeratopsCeratops is a dubious genus of ceratopsian dinosaur which lived during the Late Cretaceous. Its fossils have been found in Montana. Although poorly known, Ceratops is important in the history of dinosaurs, since it is the type species for which both Ceratopsia and Ceratopsidae are named...
) (type speciesIn 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...
)
T. prorsus
(Marsh, 1890)
Synonyms and doubtful species
The following species are considered nomina dubiaIn zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
("dubious names"), and are based on remains that are too poor or incomplete to be distinguished from pre-existing Triceratops
species.
T. albertensis
(C. M. SternbergCharles M. Sternberg was an American-Canadian fossil collector and paleontologist, son of Charles Hazelius Sternberg.Late in his career, he collected and described Pachyrhinosaurus, Brachylophosaurus, Parksosaurus and Edmontonia...
, 1949)
T. alticornis
(MarshOthniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
, 1887 [originally BisonMembers of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
])
T. eurycephalus
(SchlaikjerErich Maren Schlaikjer was an American geologist and dinosaur hunter. Assisting Barnum Brown, he co-described Pachycephalosaurus and what is now Montanoceratops. Other discoveries include Miotapirus and a new species of Mesohippus....
, 1935)
T. galeus
(Marsh, 1889)
T. hatcheri
(Lull, 1907) (contentious; see Nedoceratops
below)
T. ingens
(LullRichard Swann Lull was an American paleontologist from the early 20th century, active at Yale University, who is largely remembered now for championing a Pre-Neo-Darwinian Synthesis view of evolution, whereby mutation could unlock mysterious genetic drives that, over time, would lead populations...
, 1915)
T. maximus
(BrownBarnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...
, 1933)
T. sulcatus
(Marsh, 1890)
Misassignments
T. brevicornus
(Hatcher, 1905) (=T. prorsus
)
T. calicornis
(Marsh, 1898) (=T. horridus
)
T. elatus
(Marsh, 1891) (=T. horridus
)
T. flabellatus
(Marsh, 1889) (=T. horridus
)
T. mortuarius
(CopeEdward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
, 1874) (nomen dubium
; originally PolyonaxPolyonax was a genus of ceratopsid dinosaur from the late Maastrichtian-age Upper Cretaceous Denver Formation of Colorado, USA...
; =Polyonax mortuarius
)
T. obtusus
(Marsh, 1898) (=T. horridus
)
T. serratus
(Marsh, 1890) (=T. horridus
)
T. sylvestris
(Cope, 1872) (nomen dubium
; originally AgathaumasAgathaumas is a dubious genus of a large ceratopsid dinosaur that lived in Wyoming during the Late Cretaceous . The name comes from Greek, αγαν - 'much' and θαυμα - 'wonder'...
sylvestris
)
Nedoceratops
The paper that described Nedoceratops
was originally part of O. C. Marsh's magnum opusMasterpiece in modern usage refers to a creation that has been given much critical praise, especially one that is considered the greatest work of a person's career or to a work of outstanding creativity, skill or workmanship....
, his Ceratopsidae monographA monograph is a work of writing upon a single subject, usually by a single author.It is often a scholarly essay or learned treatise, and may be released in the manner of a book or journal article. It is by definition a single document that forms a complete text in itself...
. Unfortunately, Marsh died (1899) before the work was completed, and John Bell HatcherJohn Bell Hatcher was an American paleontologist and fossil hunter best known for discovering Torosaurus.-Biography:...
endeavored to complete the Triceratops
section. However, he died of typhusEpidemic typhus is a form of typhus so named because the disease often causes epidemics following wars and natural disasters...
in 1904 at the age of 42, leaving the paper still uncompleted. It fell to Richard Swann Lull to complete the monograph in 1905, publishing Hatcher's description of a skull separately and giving it the name Diceratops hatcheri
; Diceratops
means "two horned face."
Since the Diceratops
paper had been written by Hatcher, and Lull had only contributed the name and published the paper after Hatcher's death, Lull was not quite as convinced of the distinctiveness of Diceratops
, thinking it primarily pathological. By 1933, Lull had had second thoughts about Diceratops
being a distinct genus and he put it in a subgenus of Triceratops
: Triceratops
(Diceratops
), including T. obtusus
; largely attributing its differences to being that of an aged individual.
Because the name Diceratops
was already in use for a hymenoptera Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
n (Foerster, 1868), Andrey Sergeyevich Ukrainsky gave the animal its current name Nedoceratops
in 2007. Unaware that Ukrainsky had already re-named the animal, Octávio MateusOctávio Mateus is a Portuguese dinosaur paleontologist and biologist . He received his PhD at Universidade Nova de Lisboa in 2005...
coined another new name for it in 2008, Diceratus
. Diceratus
is thus a junior synonym of Nedoceratops
.
Opinion has varied on the validity of a separate genus for hatcheri
. John Scannella and Jack HornerJohn "Jack" R. Horner is an American paleontologist who discovered and named Maiasaura, providing the first clear evidence that some dinosaurs cared for their young. He is one of the best-known paleontologists in the United States...
regarded it as an intermediate growth stage between Triceratops
and Torosaurus
. Andrew Farke, in his 2011 redescription of the only known skull, concluded that it was an aged individual of its own valid taxon|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
, Nedoceratops hatcheri
.
Torosaurus
TorosaurusTorosaurus is a genus of ceratopsid dinosaur that lived during the late Cretaceous period , between 70 and 65 million years ago. It possessed one of the largest skulls of any known land animal. The frilled skull reached in length...
is a ceratopsid genus first identified from a pair of skulls in 1891, two years after the identification of Triceratops
. The Torosaurus
genus resembles Triceratops in geological age, distribution, anatomy and physical size and it has been recognised as a close relative. Its distinguishing features are an elongated skull and the presence of two fenestrae, or holes, in the frill. Paleontologists investigating dinosaur
ontogenyOntogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
(growth and development of individuals over the life span) in the
Hell Creek FormationThe Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...
of
MontanaMontana 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,...
, have recently presented evidence that the two actually represent a single genus.
John Scannella, in a paper presented in
BristolBristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
, UK at the conference of the
Society of Vertebrate PaleontologyThe Society of Vertebrate Paleontology was founded in 1940 for individuals with an interest in vertebrate paleontology. SVP now has almost 2,000 members. The society's website states that SVP "is organized exclusively for educational and scientific purposes...
(2009 September 25) reclassified Torosaurus
as especially mature Triceratops individuals, perhaps representing a single sex. Jack Horner, Scannella's mentor at Montana State University, noted that ceratopsian skulls consist of metaplastic bone. A characteristic of metaplastic bone is that it lengthens and shortens over time, extending and resorbing to form new shapes. Significant variety is seen even in those skulls already identified as Triceratops
, Horner said, "where the horn orientation is backwards in juveniles and forward in adults". Approximately 50% of all subadult Triceratops
skulls have two thin areas in the frill that correspond with the placement of "holes" in Torosaurus
skulls, suggesting that holes developed to offset the weight that would otherwise have been added as maturing Triceratops
individuals grew longer frills. A paper describing these findings in detail was published in July 2010 by Scannella and Horner. In it, they formally argued that Torosaurus
as well as the similar contemporary Nedoceratops
were synonymous with Triceratops
. Farke (2011) disagreed with their conclusions. He found Nedoceratops
to be distinct and the proposed changes required to "age" a Triceratops
into a Torosaurus
without precedent among ceratopsids, requiring addition of epoccipitalEpoccipital is an anatomical term for the distinctive bones found lining the frills of ceratopsid dinosaurs. The name is a misnomer, as they are not associated with the occipital bone. Epoccipitals begin as separate bones that fuse during the animal's growth to either the squamosal or parietal...
s, reversion of bone texture from adult to immature back to adult, and late growth of holes in the frill.
Ojoceratops
and Tatankaceratops
In one subsequent paper, paleontologist Nick Longrich argued that the synonymy of Triceratops
and Torosaurus
could not be supported without better intermediate forms than Scannella and Horner initially provided. Longrich did, however, agree that Nedoceratops
is a synonym of Triceratops
, and furthermore suggested that the recently described OjoceratopsOjoceratops is a genus of ceratopsian dinosaur which lived in what is now New Mexico. Ojoceratops fossils have been recovered from strata of the Ojo Alamo Formation , dating to the late Cretaceous period . The type species is Ojoceratops fowleri...
was indistinguishable from T. horridus
specimens previously attributed to the defunct species T. serratus
. Longrich suggested that another new species at the time, TatankaceratopsTatankaceratops is a controversial genus of herbivorous ceratopsian dinosaur. It is a small chasmosaurine ceratopsian which lived during the Late Cretaceous period in what is now South Dakota. It is known from a single partial skull which was collected from the Hell Creek Formation, dating to...
, possessed a strange mix of characteristics from adult and juvenile Triceratops
specimens. Longrich noted that this could represent a dwarf Triceratops
species or simply a Triceratops
specimen with a developmental disorder which caused it to stop growing prematurely.
Evolutionary origins
For many years after its discovery the evolutionary origins of Triceratops
remained largely obscure. In 1922 the newly discovered ProtoceratopsProtoceratops is a genus of sheep-sized herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs...
was seen as its ancestor by Henry Fairfield OsbornHenry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...
, but many decades passed before additional findings came to light. However, recent years have been fruitful for the discovery of several dinosaurs related to ancestors of Triceratops
. ZuniceratopsZuniceratops was a ceratopsian dinosaur from the mid Turonian of the Late Cretaceous Period of what is now New Mexico, United States...
, the earliest known ceratopsian with brow horns, was described in the late 1990s, and YinlongYinlong is a genus of basal ceratopsian dinosaur from the Late Jurassic Period of central Asia. It was a small, primarily bipedal herbivore, approximately 1.2 meters long...
, the first known JurassicThe Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
ceratopsian, in 2005.
These new finds have been vital in illustrating the origins of horned dinosaurs in general, suggesting an AsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
n origin in the Jurassic, and the appearance of truly horned ceratopsians by the beginning of the late Cretaceous in North America. As Triceratops
is increasingly shown to be a member of the long-frilled Ceratopsinae subfamily, a likely ancestor may have resembled ChasmosaurusChasmosaurus is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings in its frill . With a length of and a weight of , Chasmosaurus was a ceratopsian of average size...
, which thrived some 5 million years earlier.
Paleobiology
Although Triceratops
are commonly portrayed as herdHerd refers to a social grouping of certain animals of the same species, either wild or domestic, and also to the form of collective animal behavior associated with this or as a verb, to herd, to its control by another species such as humans or dogs.The term herd is generally applied to mammals,...
ing animals, there is currently little evidence that they lived in herds. While several other genera of horned dinosaurs are known from bonebeds preserving bones from two to hundreds or thousands of individuals, to date there is only one documented bonebed dominated by Triceratops
bones: a site in southeastern Montana with the remains of three juveniles. It may be significant that only juveniles were present.
For many years, Triceratops
finds were known only from solitary individuals. However, these remains are very common; for example, Bruce EricksonBruce R. Erickson is an American paleontologist and former Chair of Paleontology at the Science Museum of Minnesota. He retired as Chair of Paleontology in 1996. During the course of his lifetime and his 44 years as a paleontologist, he has "collected about a million specimens" and discovered...
, a paleontologist of the Science Museum of MinnesotaThe Science Museum of Minnesota is an American museum focused on topics in technology, natural history, physical science and mathematics education. Founded in 1907 and located in Saint Paul, Minnesota, the 501 nonprofit institution is staffed by over 500 employees and over 1,600 volunteers...
, has reported having seen 200 specimens of T. prorsus
in the Hell Creek FormationThe Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...
of MontanaMontana 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,...
. Similarly, Barnum BrownBarnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...
claimed to have seen over 500 skulls in the field. Because Triceratops teeth, horn fragments, frill fragments, and other skull fragments are such abundant fossils in the
Lancian faunal stageThe Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
of the late
MaastrichtianThe Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
(
late CretaceousThe Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
, 68 to 65 mya) Period of western North America, it is regarded as among the dominant herbivores of the time, if not the most dominant herbivore. In 1986, Robert Bakker estimated it as making up 5/6ths of the large dinosaur fauna at the end of the Cretaceous. Unlike most animals, skull fossils are far more common than
postcraniaPostcrania[p] in zoology and vertebrate paleontology refers to all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g...
l bones for Triceratops
, suggesting that the skull had an unusually high preservation potential.
Triceratops
was one of the last ceratopsian genera to appear before the Cretaceous-Tertiary extinction eventThe Cretaceous–Paleogene extinction event, formerly named and still commonly referred to as the Cretaceous-Tertiary extinction event, occurred approximately 65.5 million years ago at the end of the Maastrichtian age of the Cretaceous period. It was a large-scale mass extinction of animal and plant...
. The related TorosaurusTorosaurus is a genus of ceratopsid dinosaur that lived during the late Cretaceous period , between 70 and 65 million years ago. It possessed one of the largest skulls of any known land animal. The frilled skull reached in length...
, and the more distantly related diminutive LeptoceratopsLeptoceratops , was a primitive ceratopsian dinosaur genus from the Late Cretaceous Period of what is now Western North America, at the same time as its giant...
, were also present, though their remains have been rarely encountered.
Dentition and diet
Triceratops
were herbivorousHerbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, and because of their low head, their primary food was probably low growth, although they may have been able to knock down taller plantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s with their horns, beakThe beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
, and bulk. The jawThe jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s were tipped with a deep, narrow beak, believed to have been better at grasping and plucking than biting.
Triceratops
teethTeeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
were arranged in groups called batteries, of 36 to 40 tooth columns, in each side of each jaw with 3 to 5 stacked teeth per column, depending on the size of the animal. This gives a range of 432 to 800 teeth, of which only a fraction were in use at any given time (tooth replacement was continuous and occurred throughout the life of the animal). They functioned by shearing in a vertical to near-vertical orientation. The great size and numerous teeth of Triceratops
suggests that they ate large volumes of fibrous plant material, with some suggesting palmsArecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...
and cycadCycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s, and others suggesting fernA fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, which then grew in prairies.
Functions of the horns and frill
There has been much speculation over the functions of Triceratops head adornments. The two main theories have revolved around use in combat, or display in courtship, with the latter thought now to be the most likely primary function.
Early on, Lull postulated that the frills may have served as anchor points for the jaw muscles to aid chewing by allowing increased size and thus power for the muscles. This has been put forward by other authors over the years, but later studies do not find evidence of large muscle attachments on the frill bones.
Triceratops were long thought to have possibly used their horns and frills in combat with predators such as
TyrannosaurusTyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
, the idea being discussed first by
C. H. SternbergCharles Hazelius Sternberg , was an American fossil collector and amateur paleontologist. His older brother, Dr. George M. Sternberg was a military surgeon assigned to Fort Harker near Ellsworth, Kansas and brought the rest of Sternberg family to Kansas to live on his ranch about 1868...
in 1917 and 70 years later by Robert Bakker. There is evidence that
Tyrannosaurus did have aggressive head-on encounters with
Triceratops, based on partially healed tyrannosaur tooth marks on a
Triceratops brow horn and
squamosalThe 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,...
; the bitten horn is also broken, with new bone growth after the break. Which animal was the aggressor is not known.
Tyrannosaurus is also known to have fed on
Triceratops. Evidence for this includes a heavily tooth-scored
Triceratops iliumThe ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
and
sacrumIn vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
.
In addition to combat with predators using horns,
Triceratops are classically shown engaging each other in combat with horns locked. While studies show that such activity would be feasible, if unlike that of present-day horned animals, there is disagreement about whether they actually did so. Additionally, although pitting, holes, lesions, and other damage on
Triceratops skulls (and the skulls of other ceratopsids) are often attributed to horn damage in combat, a recent study finds no evidence for horn thrust injuries causing these forms of damage (for example, there is no evidence of infection or healing). Instead, non-pathological
bone resorptionBone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....
, or unknown bone diseases, are suggested as causes. However, a newer study compared incidence rates of skull lesions and
periosteal reactionA periosteal reaction is the formation of new bone in response to injury or other stimuli of the periosteum surrounding the bone. It is most often identified on X-ray films of the bones.-Etiology:...
in
Triceratops and
CentrosaurusCentrosaurus is a genus of herbivorous ceratopsian dinosaurs from the late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation and uppermost Oldman Formation, dating from 76.5 to 75.5 million years ago....
and showed that these were consistent with
Triceratops using its horns in combat and the frill being adapted as a protective structure, while lower pathology rates in
Centrosaurus may indicate visual rather than physical use of cranial ornamentation, or a form of combat focused on the body rather than the head. The researchers also concluded that the damage found on the specimens in the study was often too localized to be caused by bone disease.
The large frill also may have helped to increase body area to
regulate body temperatureThermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
. A similar theory has been proposed regarding the plates of
StegosaurusStegosaurus is a genus of armored stegosaurid dinosaur. They lived during the Late Jurassic period , some 155 to 150 million years ago in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well...
, although this use alone would not account for the bizarre and extravagant variation seen in different members of the
CeratopsidaeCeratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
. This observation is highly suggestive of what is now believed to be the primary function, display.
The theory of their use in sexual display was first proposed by Davitashvili in 1961 and has gained increasing acceptance since. Evidence that visual display was important, either in courtship or in other social behavior, can be seen in the fact that horned dinosaurs differ markedly in their adornments, making each species highly distinctive. Also, modern living creatures with such displays of horns and adornments use them in similar behavior. A recent study of the smallest
Triceratops skull, ascertained to be a juvenile, shows the frill and horns developed at a very early age, predating sexual development and thus probably important for visual communication and species recognition in general.
Depiction in recent popular media
The distinctive appearance of
Triceratops has led to them being frequently depicted in films, computer games and documentaries, including the
Don BluthDonald Virgil "Don" Bluth is an American animator and independent studio owner. He is best known for his departure from The Walt Disney Company in 1979 and his subsequent directing of animated films such as The Secret of NIMH , An American Tail ,The Land Before Time , and All Dogs Go to Heaven ,...
film
The Land Before TimeThe Land Before Time is a 1988 American animated adventure film directed and co-produced by Don Bluth , and executive-produced by Steven Spielberg, George Lucas, Kathleen Kennedy, and Frank Marshall....
, which featured a young
Triceratops as a main character, the 1993 film
Jurassic ParkJurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg. The film is based on the novel of the same name by Michael Crichton. It stars Sam Neill, Laura Dern, Jeff Goldblum, Richard Attenborough, Martin Ferrero, and Bob Peck...
and the 1999
BBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
television documentary
Walking with DinosaursWalking with Dinosaurs is a six-part documentary television miniseries that was produced by BBC, narrated by Kenneth Branagh, and first aired in the United Kingdom, in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that...
.
Triceratops (the species are not identified) is the official
state fossilMost American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single species....
of
South DakotaSouth Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
, and the official state dinosaur of
WyomingWyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
.
A recurring theme, especially in children's dinosaur books, is a climactic showdown or battle between
Triceratops and
Tyrannosaurus. In 1942,
Charles R. KnightCharles Robert Knight was an American artist best known for his influential paintings of dinosaurs and other prehistoric animals...
painted a mural incorporating a confrontation between the two dinosaurs in the
Field Museum of Natural HistoryThe Field Museum of Natural History is located in Chicago, Illinois, USA. It sits on Lake Shore Drive next to Lake Michigan, part of a scenic complex known as the Museum Campus Chicago...
for the
National Geographic SocietyThe National Geographic Society , headquartered in Washington, D.C. in the United States, is one of the largest non-profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the promotion of environmental and historical...
, establishing them as enemies in popular thought. Paleontologist Bob Bakker said of the imagined rivalry between
Tyrannosaurus and
Triceratops, "No matchup between predator and prey has ever been more dramatic. It's somehow fitting that those two massive antagonists lived out their co-evolutionary belligerence through the very last days of the very last epoch of the Age of Dinosaurs."
External links