Laosaurus
Encyclopedia
Laosaurus is a genus
of hypsilophodont
dinosaur
. The type species is Laosaurus celer, first described by O.C. Marsh
in 1878 from remains from the Oxfordian
-Tithonian
-age Upper Jurassic Morrison Formation
of Wyoming
. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species from the Morrison Formation, L. gracilis, and a species from the late Cretaceous
of Alberta
, Laosaurus minimus, are also considered dubious
. It is believed that the three species were hypsilophodont
s, basal
ornithopod
s.
at Como Bluff
, Wyoming
, from rocks of the Morrison Formation
. The type
material includes nine partial and two complete tail vertebral centra
, which he concluded came from a "fox
-sized" animal. In the same year, he named two other species: L. gracilis, originally based on a back vertebral centrum, a tail vertebral centrum, and part of an ulna
; and L. altus, originally based on a pelvis
, hindlimb, and tooth (YPM 1876). A review by Peter Galton
in 1983 found the type of L. gracilis to consist of thirteen back and eight tail centra, and portions of both hindlimbs. Charles Gilmore
had assigned additional remains, including a partial skeleton (CM
11340), to L. gracilis based on size, but Galton transferred the remains to other taxa, assigning the skeleton to Dryosaurus.
Marsh returned to the genus in 1894, when additional remains convinced him that L. altus deserved its own genus (Dryosaurus
), and that there was another species present: L. consors, based on YPM 1882, a partial skeleton also from Como Bluff. In 1895, he coined the family Laosauridae for his genus, but this was eventually considered synonymous with Hypsilophodontidae.
Charles Gilmore in 1909 assigned a juvenile femur
(USNM
5808) to L. gracilis, and in 1925 added partial skeleton CM 11340 to L. gracilis, based on size, but Galton transferred the femur to Othnielia
and the skeleton to Dryosaurus in 1983. Gilmore also described the fifth and final species, L. minimus (species name for its small size), based on NMC
9438, a partial left hindlimb and vertebral bits from the Oldman Formation
(Upper Cretaceous, middle Campanian
-age) of Alberta
, Canada
. At the time, though, the discovery locality was thought to be in the Lower Cretaceous Blairmore Formation, which may partially explain why Gilmore chose to assign the remains to the late Jurassic genus Laosaurus. Loris Russell in 1949 pointed out the new geological information and disputed the generic assignment, recommending that it be referred to as "Laosaurus" minimus. He found it to be most like Hypsilophodon
, from the Lower Cretaceous Wealden
of England
.
The next major publications which mentioned Laosaurus prominently were by Galton. In 1977, he assigned L. consors and L. gracilis to his new taxon
Othnielia rex
; and in 1983 he redescribed most of the material and reassigned some of it, as described above. Galton (1983) is also one of the sources for the "Troodon
as carnivorous
ornithopod
" hypothesis
of the early 1980s, because it assigns L. minimus to Troodon, based on unpublished evidence. This would tie in with the Orodromeus
/Troodon
egg
confusion of a few years later, which was eventually settled as Troodon individuals eating Orodromeus individuals at their nesting site (the troodontid embryo
es were confused with hypsilophodont embryoes). L. celer was assessed as dubious by Galton, a status it has kept through the last major reviews.
Two further developments have occurred. First, L. minimus is seen as a possible second species or specimen of Orodromeus
(Sues and Norman, 1990), although the remains are too meager to be certain. Second, Galton, in a 2007 review, declared Othnielia rex to be based on undiagnostic remains, and shifted diagnostic referred remains to new taxon Othnielosaurus consors
, a new combination based on the original L. consors partial skeleton.
al cursorial
herbivore
s.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...
dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
. The type species is Laosaurus celer, first described by O.C. Marsh
Othniel Charles Marsh
Othniel 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...
in 1878 from remains from the Oxfordian
Oxfordian stage
The Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 161.2 ± 4 Ma and 155.7 ± 4 Ma...
-Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
-age Upper Jurassic Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
of Wyoming
Wyoming
Wyoming 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...
. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species from the Morrison Formation, L. gracilis, and a species from the late Cretaceous
Late Cretaceous
The 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...
of Alberta
Alberta
Alberta 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...
, Laosaurus minimus, are also considered dubious
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
. It is believed that the three species were hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...
s, basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
s.
History and taxonomy
Marsh (1878a) named his new genus from vertebrae (YPM 1874) found by Samuel Wendell WillistonSamuel Wendell Williston
Samuel Wendell Williston was an American educator and paleontologist who was the first to propose that birds developed flight cursorially , rather than arboreally . He was also an entomologist, specialising in Diptera.-Early life:Williston was born in Boston, Massachusetts to Samuel Williston and...
at Como Bluff
Como Bluff
Como Bluff is a long ridge extending east-west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing...
, Wyoming
Wyoming
Wyoming 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...
, from rocks of the Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
. The type
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
material includes nine partial and two complete tail vertebral centra
Body of vertebra
The body is the largest part of a vertebra, and is more or less cylindrical in shape. For vertebrates other than humans, this structure is usually called a centrum....
, which he concluded came from a "fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...
-sized" animal. In the same year, he named two other species: L. gracilis, originally based on a back vertebral centrum, a tail vertebral centrum, and part of an ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
; and L. altus, originally based on a pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
, hindlimb, and tooth (YPM 1876). A review by Peter Galton
Peter Galton
Peter M. Galton is a British vertebrate paleontologist working in America, who has to date written or co-written about a hundred papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosauropod dinosaurs.With Robert Bakker in a joint article...
in 1983 found the type of L. gracilis to consist of thirteen back and eight tail centra, and portions of both hindlimbs. Charles Gilmore
Charles W. Gilmore
Charles Whitney Gilmore was an American paleontologist, who named dinosaurs in North America and Mongolia, including the Cretaceous sauropod Alamosaurus, Alectrosaurus, Archaeornithomimus, Bactrosaurus, Brachyceratops, Chirostenotes, Mongolosaurus, Parrosaurus, Pinacosaurus, Styracosaurus and...
had assigned additional remains, including a partial skeleton (CM
Carnegie Museum of Natural History
Carnegie Museum of Natural History, located at 4400 Forbes Avenue in the Oakland neighborhood of Pittsburgh, Pennsylvania, USA, was founded by the Pittsburgh-based industrialist Andrew Carnegie in 1896...
11340), to L. gracilis based on size, but Galton transferred the remains to other taxa, assigning the skeleton to Dryosaurus.
Marsh returned to the genus in 1894, when additional remains convinced him that L. altus deserved its own genus (Dryosaurus
Dryosaurus
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont . Fossils have been found in the western United States, and were first discovered in the late 19th century...
), and that there was another species present: L. consors, based on YPM 1882, a partial skeleton also from Como Bluff. In 1895, he coined the family Laosauridae for his genus, but this was eventually considered synonymous with Hypsilophodontidae.
Charles Gilmore in 1909 assigned a juvenile femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
(USNM
National Museum of Natural History
The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. Admission is free and the museum is open 364 days a year....
5808) to L. gracilis, and in 1925 added partial skeleton CM 11340 to L. gracilis, based on size, but Galton transferred the femur to Othnielia
Othnielia
Othnielia is a genus of ornithischian dinosaur, named after its original describer, Professor Othniel Charles Marsh, an American paleontologist of the 19th century...
and the skeleton to Dryosaurus in 1983. Gilmore also described the fifth and final species, L. minimus (species name for its small size), based on NMC
Canadian Museum of Nature
The Canadian Museum of Nature is a natural history museum in Ottawa, Ontario, Canada. Its collections, which were started by the Geological Survey of Canada in 1856, include all aspects of the intersection of human society and nature, from gardening to gene-splicing...
9438, a partial left hindlimb and vertebral bits from the Oldman Formation
Oldman Formation
The Oldman Formation is the middle member of the Judith River Group, a major geologic unit in southern Alberta. The formation is widely recognized as bearing a great number of well preserved dinosaur skeletons, as well as other fossils.-Age:...
(Upper Cretaceous, middle Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
-age) of Alberta
Alberta
Alberta 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...
, Canada
Canada
Canada 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...
. At the time, though, the discovery locality was thought to be in the Lower Cretaceous Blairmore Formation, which may partially explain why Gilmore chose to assign the remains to the late Jurassic genus Laosaurus. Loris Russell in 1949 pointed out the new geological information and disputed the generic assignment, recommending that it be referred to as "Laosaurus" minimus. He found it to be most like Hypsilophodon
Hypsilophodon
Hypsilophodon is an ornithopod dinosaur genus from the Early Cretaceous period of Europe. It was a small bipedal animal with an herbivorous or possibly omnivorous diet...
, from the Lower Cretaceous Wealden
Wealden
For the stone, see Wealden GroupWealden is a local government district in East Sussex, England: its name comes from the Weald, the area of high land which occupies the centre of its area.-History:...
of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
The next major publications which mentioned Laosaurus prominently were by Galton. In 1977, he assigned L. consors and L. gracilis to his new taxon
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...
Othnielia rex
Othnielia
Othnielia is a genus of ornithischian dinosaur, named after its original describer, Professor Othniel Charles Marsh, an American paleontologist of the 19th century...
; and in 1983 he redescribed most of the material and reassigned some of it, as described above. Galton (1983) is also one of the sources for the "Troodon
Troodon
Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous period . Discovered in 1855, it was among the first dinosaurs found in North America...
as carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
" hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
of the early 1980s, because it assigns L. minimus to Troodon, based on unpublished evidence. This would tie in with the Orodromeus
Orodromeus
Orodromeus is a genus of herbivorous ornithopod dinosaur from the Late Cretaceous of North America.-Discovery and naming:...
/Troodon
Troodon
Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous period . Discovered in 1855, it was among the first dinosaurs found in North America...
egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
confusion of a few years later, which was eventually settled as Troodon individuals eating Orodromeus individuals at their nesting site (the troodontid embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
es were confused with hypsilophodont embryoes). L. celer was assessed as dubious by Galton, a status it has kept through the last major reviews.
Two further developments have occurred. First, L. minimus is seen as a possible second species or specimen of Orodromeus
Orodromeus
Orodromeus is a genus of herbivorous ornithopod dinosaur from the Late Cretaceous of North America.-Discovery and naming:...
(Sues and Norman, 1990), although the remains are too meager to be certain. Second, Galton, in a 2007 review, declared Othnielia rex to be based on undiagnostic remains, and shifted diagnostic referred remains to new taxon Othnielosaurus consors
Othnielosaurus
Othnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologist Othniel Charles Marsh, and was formerly assigned to the genus...
, a new combination based on the original L. consors partial skeleton.
Taxonomic summary
- L. celer (type species) = dubiousNomen dubiumIn zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
basal ornithopod - L. altus = Dryosaurus altusDryosaurusDryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont . Fossils have been found in the western United States, and were first discovered in the late 19th century...
- L. consors = Othnielosaurus consorsOthnielosaurusOthnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologist Othniel Charles Marsh, and was formerly assigned to the genus...
- L. gracilis = unknown (gracilis predates consors, which would require a name change if referred to Othnielosaurus consors), probably a dubious basal ornithopod
- L. minimus = dubious basal ornithopod, possibly the same as Orodromeus
Paleobiology
Too little of the various species is known to make any detailed assessments, but as hypsilophodonts or basal ornithopods, they were probably small, bipedBiped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
al cursorial
Cursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
herbivore
Herbivore
Herbivores 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...
s.
External links
- More on the taxonomy of Nanosaurus, Othnielia, and Laosaurus, from the Dinosaur Mailing List
- First page and abstract of Russell, 1949